EE 477 Final Report - Purdue Engineering 477 Final Report Fall 2010 Team 6 Defender ... 1.0 Project Overview and Block Diagram ... The camera for target tracking is a Canon VC-C50i[1]

ECE 477 Final Report Fall 2010

Team 6 Defender

Team Members:

#1: Stephen Wolf________________ Signature: ____________________ Date: _________

#2: Kirk Iler____________________ Signature: ____________________ Date: _________

#3: Fuhe Xu____________________ Signature: ____________________ Date: _________

#4: Brian Bentz_________________ Signature: ____________________ Date: _________

CRITERION SCORE MPY PTS

Technical content 0 1 2 3 4 5 6 7 8 9 10 3

Design documentation 0 1 2 3 4 5 6 7 8 9 10 3

Technical writing style 0 1 2 3 4 5 6 7 8 9 10 2

Contributions 0 1 2 3 4 5 6 7 8 9 10 1

Editing 0 1 2 3 4 5 6 7 8 9 10 1

Comments: TOTAL

ECE 477 Final Report Spring 2011

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TABLE OF CONTENTS

Abstract 1

1.0 Project Overview and Block Diagram 1

2.0 Team Success Criteria and Fulfillment 3

3.0 Constraint Analysis and Component Selection 3

4.0 Patent Liability Analysis 8

5.0 Reliability and Safety Analysis 11

6.0 Ethical and Environmental Impact Analysis 14

7.0 Packaging Design Considerations 17

8.0 Schematic Design Considerations 20

9.0 PCB Layout Design Considerations 23

10.0 Software Design Considerations 26

11.0 Version 2 Changes 29

12.0 Summary and Conclusions 30

13.0 References 31

Appendix A: Individual Contributions A-1

Appendix B: Packaging B-1

Appendix C: Schematic C-1

Appendix D: PCB Layout Top and Bottom Copper D-1

Appendix E: Parts List Spreadsheet E-1

Appendix F: FMECA Worksheet F-1


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Abstract

Defender is a turret-mounted coilgun-based security system featuring automated target

tracking. The primary goal of Defender is automated deterrence, and this is accomplished by

identifying targets, aiming the barrel of the coilgun, and propelling projectiles with

electromagnetic force. A user issues commands to the system through a simple interface on a

remote laptop connected to the system through an Ethernet connection. The system features an

option for both manual user control and automatic targeting. With a multitude of functionality,

Defender provides the user with a relatively inexpensive, reliable autonomous security system.

1.0 Project Overview and Block Diagram

The unit is overseen through a remote computer user interface allowing the ability to

choose between multiple modes of operation. In autonomous mode the unit will use an

embedded processor and camera to display and identify targets while following those targets

with a turret. In manual mode the user will send control signals to the processor for moving the

motors, targeting, and controlling the capacitor charging circuit. The user interface

communicates with the embedded Intel Atom processor handling the image processing and

command structure. The Atom processor then communicates with the microcontroller over a

USB interface. The microcontroller communicates over I2C with the motors, capacitors, and

sensing mechanisms.

The high voltage capacitor system is implemented with the ability to charge up to 400

volts, slowly discharge, or pulse current through a coil. When pulsed through a coil, the

electromagnetic force will propel a projectile at high speeds towards a target. The barrel and coil

housing is mounted on a two axis turret which utilizes stepper motors for fine position control.

As the system’s operation is potentially dangerous, a multitude of safety measures are

implemented on the system for user protection.


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Figure 1-1: Block Diagram

Figure 1-2: Completed Project


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2.0 Team Success Criteria and Fulfillment

1. An ability to fire a projectile using electromagnetic force

2. An ability to aim the projectile by controlling of the azimuth and elevation angles of the

barrel

3. An ability to charge a capacitor bank to a variable voltage, up to 400V

4. An ability to gather images and perform target recognition and tracking

5. An ability for a user to enter commands and display the status of the turret through an

external interface

The Defender system successfully completes the criteria of charging a capacitor bank to a

variable high voltage, gathering images and performing target recognition, controlling a two axis

turret, and displaying the status of the system through an external user interface.

The ability to fire a projectile using electromagnetic force is fully implemented, and the

team has no reason to believe it would not expel a projectile at a high speed. 500 amps were

successfully pulsed through a coil during a high voltage test. Due to time and safety constraints, the

firing of the projectile was delayed to a later date. As of the time of the writing of this report, the

team has not attempted to expel a projectile with the current through the coil.

3.0 Constraint Analysis and Component Selection

3.1 Introduction

Defender is a turret based defense system for high security installations. A computer base

station interfaces with an onboard atom processor which controls the coilgun turret system.

Onboard the turret system is an Atom processor to deal with the requirements of the image

processing software for target tracking and identification. The coilgun consists of a custom made

barrel and coil, a capacitor bank contained in insulators for protection, a high voltage adjustable

power supply, and a solid state discharge circuit. The turret itself consists of two stepper motors

controlled with their own specialized microcontroller for control of the azimuth and elevation

angles. A microcontroller will act as a master to communicate commands from the Atom board

to the various systems and to report back their status. There are also other minor components

present such as a speaker for auditory warnings and a keypad for entering PINs (Personal

Identification Numbers). An updated block diagram of the system can be found in appendix B.

3.2.0 Design Constraint Analysis

There are five major tasks that the Defender system must be able to accomplish; these

will be the main focus of this report. Those five are computation, communication, charging,

control of motors, and discharging. The computation is discussed in section 2.1. Devices for

communication (microcontroller options), charging (DC-DC converter), controlling of the


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motors (through a stepper motor IC), and discharging (IGBT options) are discussed in section

3.0. Besides those constraints induced by safety we have no particular weight, space, or

packaging constraints. The system is not currently designed for any particular area or hallway

and as such is only a general prototype without any of the size constraints a final physical

location would contain. However, it is desirable to make the barrel as light as possible to avoid

needing more powerful motors. More details on packaging design and constraint will be found in

section 2.6.

3.2.1 Computation Requirements

The Defender system has a significant computation requirement in its image processing,

taking in at least 60 frames per second. The ultimate goal of the cameras available to the system

is to take the image, identify anything in the image that is considered a target, construct a 3-D

position of the target based on a previously known size, and if necessary move the barrel or assist

the user in firing upon this target. All of these must be done in real time on a moving target and

communicate to the motors so that they can move quickly enough to track the target. The

objective for this prototype is for all of this to take place quickly enough to catch targets moving

at 1 m/s or less at a distance of 2-5m. In order to achieve this level of computation an onboard

Atom processor will be utilized. This processor will also serve as the communication hub as

described in section 2.2. All other computations are simple tasks, such as tracking motor position

based on commanded steps or calculating the voltage required to achieve a certain projectile

speed. The microcontroller itself has no real-time computation constraints that any 8 or 16bit

microcontroller cannot achieve.

3.2.2 Interface Requirements

The turret main system has three levels of devices that interface with each other. On the

top level is the PC base station which talks through Ethernet cable to an existing port on the

Atom board. The second level consists of the devices which will be connected to the Atom board

itself. The primary communication method of the Atom board to its peripherals is USB; both the

cameras and the master microcontroller will interface to the Atom board through the USB inputs

available. The microcontroller itself will then be communicating to its peripherals primarily

through a single master multi slave I2C bus. Some of the slave devices will be port expanders and

ADCs. A serial header for BDM will also be present on the board. We chose I2C because it is a

simple protocol without any serious current requirements and requires no special level

translators. USB requires special regulators to create the 3.3V necessary but all such hardware is

contained within the USB module on the microcontroller itself.

3.2.3 On-Chip Peripheral Requirements

The master microcontroller has two critical requirements: built in USB support and I2C

support. Only one USB module is needed to communicate with the Atom board. The chip will

require multiple external interrupts and timers, but there is nothing major constraining the


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devices besides the USB and I2C support. Any device which supports USB will likely have the

amount of pins, interrupts, and timers we need. Virtually all other functionality will be off loaded

from this chip onto external devices as detailed in section 2.4.

3.2.4 Off-Chip Peripheral Requirements

Defender will have a multitude of off-chip secondary devices that are all controlled either

directly through an I2C bus or through I

2C port expanders. To measure the voltage of the

capacitor bank we will use a resistor divider network connected to external ADC which

communicates to the microcontroller over I2C. This is necessary since the capacitor voltage is on

a different board than the microcontroller and I do not want to hook the high voltage directly to

the microcontroller ADC. Photodiodes and IR diodes will be present in the barrel for monitoring

the position and speed of the projectile. A special purpose IC for stepper motor control is

required to operate and monitor the stepper motors. A keypad encoder will also be utilized to

monitor the keypad for entering PINs. The camera for target tracking is a Canon VC-C50i[1]

with

its own Pan/Tilt/Zoom stage and requires no support besides the USB interface.

3.2.5 Power Constraints

Defender will be powered straight from the wall with a standard AC cable. While the

basic 12V and 3.3V rails for component operation are simple and have no particular concern, the

charging and discharging of the capacitor bank requires many special components and

precautions. The capacitor bank will consist of four 3900 µF U32L capacitors rated to 400V. A

high voltage transformer will be used to step up the voltage from the wall and this will be

rectified used to directly charge the capacitors. A triac switching current before rectification will

be used to turn the charging on and off. This capacitor bank will have to be well shielded to

prevent against both EMI. Due to the short nature of our pulses (<10ms) heat dissipation is not a

primary concern in the capacitors. Discharging the capacitors into the coil around the barrel will

be done through a solid state switch, specifically an IGBT. This IGBT will have to rated for at

least 500A and will be heatsinked using the chassis.

3.2.6 Packaging Constraints

There are no weight or space constraints on Defender besides those that would make it

impossible to eventually ceiling mount it as a defensive turret. There is very little recoil force on

our device due to the extremely low mass of our projectile so we do not have to worry about

being too light either. Therefore choices should be made to lessen weight were possible but this

is not an overriding priority as the maximum weight depends very much on where the turret

would be installed. The weight of the barrel and the stage that holds the barrel are however both

critical. These weights should be minimized as to reduce the stepper motor size and current

required. The primary packaging constraint is then safety. The capacitor bank is to be charged to

very high voltages and the barrel will be having large currents pass through as well as heating up.


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Electromagnetic shielding must also be used so as to not disrupt any nearby devices due to the

large pulses of energy associated with firing the device.

3.2.7 Cost Constraints

While similar systems exist in the realm of remotely operated turrets, such devices do not

normally have their prices freely disclosed and also contain much more advanced sensor

equipment as well as redundancies when compared to the prototype Defender. Two traditional

turret based systems are the TRT-25MM[2]

from BAE systems and the WASP[3]

from a French

company known as Panhard. BAE systems does not give an estimate of how much the TRT-

25MM costs but an article[4]

from the Defense News of Army Times Publishing Company quotes

the WASP at $62,000 per unit, far and above the estimate of $750 our prototype carries. This

price difference is the extra cost of R&D, manufacturability, and the reliability that the military

requires.

3.3 Component Selection Rationale

There are three microcontrollers that were looked at to act as the primary controller. The

MC9S08JM60(S08) from Freescale, the PIC18F65J50(PIC18) from Microchip, and the

PIC24FJ64GB004(PIC24) also from Microchip. These three were selected as having both USB

and I2C support, the availability in packages that are easy to solder such as 44 pin TQFP, the

availability of other useful peripherals such as ADCs and timer channels, and then selecting

those with the highest amounts of Flash and RAM to allow for significant overhead. Also

important considerations are the availability of an embedded C compiler and SDK for the

device, and debugging modes. The PIC24[5]

is the device selected to be used in Defender

primarily because of its 16 bit architecture where the PIC18 and the S08 are both 8 bit

architectures. All three chips have the necessary peripherals but the PIC24 has two I2C channels,

more timers and PWM channels, and the most flash and RAM. Instead of a standard USB

module the PIC24 also has a USB on the go module which allows for the possibility of the

microcontroller to become a USB host if further USB devices were integrated into the design.

The PIC24 is available in a compact 28pin SOIC package (24FJ64GB002) but the package that

will be used in the design is a 44pin TQFP(24FJ64GB004). The availability of more remap-able

pins will be useful in the case of any further design changes. The PIC24 and the S08 are both

the same price, around $5, with the PIC18 being slightly cheaper at $4. Samples are available

for the PIC24 and pricing is not an issue for this prototype.

We will be using a high voltage transformer to step up wall voltage to 360V rms in order

to charge our capacitor bank. A rectifier will be placed in front of this to only apply positive

voltage to the capacitor and we will also need a resistor to limit inrush current. A high power

triac will be used to switch the AC voltage on and off. This triac is controlled through an

optically isolated triac driver. While not the most optimal charging solution it is extremely

simplistic and allows us to charge our capacitors up to 400V in less than a minute.


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Two stepper motor drivers were looked at, the A3988 from Allegro Microsystems and

the DRV8821 from Texas Instruments. These chips are both PWM drivers for dual bipolar

stepper motors with capacities of up to 1.5A at 35V, more than enough power for our motors.

Our motors are 400mA motors that are capable of 2kg-cm of torque at those ratings, which

should be sufficient to move our barrel. The devices have packaged H-Bridges that allow for the

driving of stepper motors at high currents. The DRV8821[7]

is chosen for our application due to

its simpler control scheme of simple positive edges for steps and a voltage reference for current

limiting, the ability to achieve microstepping with 1/8 steps, and the packaging of the heatsinks

external to the chip with no pad underneath the IC. Samples are also available from TI.

The IGBT acts as a high voltage high current solid state switch to discharge the capacitor

bank into the coil surrounding the barrel. A cheaper option than an IGBT would have been to go

with an SCR. An SCR however cannot be turned off until a certain energy limit and requires

significantly more calibration than an IGBT module. Three IGBT’s were looked at, the

APT200GN60JDQ4 from Microsemi, the APTGT300SK60D3G also from Microsemi and the

SEMIX 453GAL12E4S from Semix. The maximum voltage from the capacitors is 400V while

the maximum pulsed current through the barrel is estimated at 300-600A. The SEMIX IGBT

has the highest ratings with 1200V and up to 1350A pulsed, 685A continuous. This module

would be guaranteed to not break but is extremely expensive at $215.48. The APTGT300

module is lower rated at 600V and 600A pulse, 400A continuous. However this module is also

expensive at the $155 price range. The reason that those two IGBT’s are so expensive is that

they come with massive attached heatsinks. The vast majority of the heat will be dissipated in

our coil as it contains the most resistance and not our IGBT. Our pulses are also very short

(<20ms) and therefore we go with the APT200 module[8]

. This module is rated even lower than

the APTGT300 with 600V and 600A pulse, 283 continuous, but these ratings are still more than

sufficient for our application as we are designing for a maximum firing current of 500A. It

comes in an ISOTOP package meant to mount directly to a chassis and is much more reasonably

priced at $42 per module.

3.4 Summary

The Defender turret system will give it’s user the ability to control and fire a coilgun

based turret while also having the automated capacity of tracking and firing at targets. Personnel

will have PINs to bypass the turret and prove to the user that they are allowed past the

checkpoint. Many of the components in the Defender system are either custom, like the

barrel/coil, or have already been donated or found in surplus, such as the cameras and capacitors.

This report looks at the other major components of the project and how they can best fit in terms

of functionality, cost, and safety. The PIC 24FJ64GB004 will be the primarily microcontroller in

the turret, communicating with an Atom board for image processing and a TI DVR8821 for

motor control. The power supply proved very difficult to locate an appropriate IC and will be

custom designed so that the charging of the capacitors can be achieved in a reasonable time

frame. Discharging will be done through a Microsemi IGBT, the APT200GN60JDQ4.


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4.0 Patent Liability Analysis

4.1 Introduction

The Defender turret based defense system consists of many areas of functionality, each of

which must be analyzed for potential patent infringement if the product were intended to be

brought to market. The general functionality of the Defender consists of utilizing a target

recognition system to aim a coilgun weapon and fire at a target. It also consists of a user

identification system used to enable and gain access to the weapon. The potential liability for

Defender mostly exists within the methods and implementations of combining certain features of

the device, as the device itself contains mostly basic functionality. Patents must be reviewed in

order to investigate the potential liability in the implementation of the functions of Defender.

Similar products must also be analyzed in order to investigate any relevant patents pending or

issued, and to get a sense for the prior art in the field. Utilizing the information gathered from

these sources, the Defender team looks to analyze potential liability in the case that the product

was to be taken to market.

4.2 Results of Patent and Product Search

The first patent of relevance to the Defender project claims a method of implementing an

autonomous weapon system. This patent, United States Patent 7210392[9]

, was filed on October

17, 2001 and subsequently published on May 1, 2007. The patent describes a weapon system

utilizing sensors to acquire images, processing this data to find targets, and controlling the

weapon to aim and fire at any identified relevant targets. The patent discusses full automation,

allowing functionality without user input.

Claim Language:

An autonomous weapon system that can engage targets without human intervention

A sensor system to acquire image data

Identify potential targets

Provide control signals

Autonomous firing control

Further peripheral functionality not of particular relevance to the production of Defender

is addressed in the other claims of the patent.

The second patent examined claims an implementation of weapon firing safeties and

methods of operating the same. This patent, United States Patent 7600339[10]

, was filed on

November 22, 2006 and published on October 13, 2009. The patent describes a method of

implementing weapon identification codes to communicate between a weapon system and a host.


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The patent primarily addresses utilizing identification codes to discern between and allow

enabling of multiple weapons individually.

Claim Language:

Enabling a weapon to shoot

A weapon identification code

Includes at least one registered weapon identification

Transmit an enabling signal to the safety device in the weapon

As with the first patent, further periphery functionality is given that is not of particular

relevance to the Defender project.

Many of the products with functionality similar to Defender are complex military

devices, but a commercial device was found that takes the form of a paintball gun. The Sentry

Project’s Paintball Sentry [11]

contains many functions similar to the implementation of Defender.

The product can be summarized as a turret mounted, target tracking paintball gun. It contains a

camera for target recognition and tracking, a rotating firing barrel, and a computer interface. The

Paintball Sentry device implements the same basic functions of the Defender device as

previously listed, utilizing a paintball gun instead of a coilgun. The manufacturer of the

Paintball Sentry was contacted, but stated that there were no patents involved with the device.

He further went on to imply that no existing patents were of particular concern to him in making

the devices. The argument was made that many products and hobbyist projects exist with similar

functionality, which implies that he thinks that the prior art in the field covers manufacturability

of the device.

4.3 Analysis of Patent Liability

It is difficult to determine whether infringement of the patent on a method of

implementing an autonomous weapon system exists. Differences can be argued between the

implementation of the Defender autonomous state and the patent autonomous state description.

The Defender implementation is a temporary semi-autonomous state that is enabled by the user.

When enabled, Defender fires one time, and then control will revert to the user to issue further

commands. It could be argued that the form of semi-autonomy present in the Defender design

does not satisfy the condition in the patent of full automation without user input. Defender does

contain some literally infringing functions such as having an automatic mode with target

recognition, aiming, and firing, but these are fairly general functions that would seem to exist in

any device of this nature. As the primary claim addresses mostly these general functions, it

becomes difficult to clarify the scope of this patent as it applies to basic functionality in the field,

as in Defender’s case. The prior art would have to be thoroughly reviewed in order to examine

precisely what functionality this patent is claiming and ensure that Defender does not infringe.

The patent on an implementation of weapon firing safeties and methods of operating the

same is relevant due to an enabling mechanism of Defender. Enabling Defender functionality


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consists of utilizing a password or personal identification code on the weapon, input through a

keypad. The argument of a password and a code for identification of a weapon type could

possibly be argued as infringing under the doctrine of equivalents if the user input allows

recognizing and discerning the particular type of device attached from other devices. The claim

language particularly addresses ―at least one registered weapon identification‖, but the

abstraction of weapon identification for only one device arguably does not hold much weight.

Since our product does not consist of multiple devices with different passwords to enable

different devices, the potential for liability due to violation of this patent is negligible as the

Defender design currently stands. It is still worth noting this patent to ensure that future

adaptation and change in functionality of Defender does not infringe.

The Paintball Sentry was the commercial product found to be most similar to our device

in functionality. Defender and the Paintball Sentry both consist of a turret mounted weapon that

performs target recognition in order to aim and fire at targets. The Paintball Sentry is designed

to interface with most trigger based guns, while Defender is only designed to interface with a

coilgun, which has no mechanical triggering mechanism. The basic functionality of these

devices would likely be similar to any non-military automated weapon device, and thus the

potential for infringement is low due to the amount of prior art in the field.

4.4 Action Recommended

The patent on an autonomous weapon system is the patent of the most concern to the

Defender project. The primary claim in the patent addresses essentially the entire functionality

of our product, generalized for any type of weapon. Since the scope of the patent addresses very

generalized functionality of automated targeting systems, more investigation into liability would

be necessary. Certainly the prior art in the field must cover some of the basic functionality

necessary in devices like Defender. The final verdict would likely be that either the patent is

addressing extremely specific forms of functionality not covered by the prior art, or that the

patent itself is too generalized and thus invalid. The best course of action would be to contact an

individual with knowledge and expertise in the prior art in the field of automated weapon

systems.

The patent on an implementation of weapon firing safeties and methods of operating the

same is only of marginal concern to the design of Defender. In expanding product functionality,

there may be concern of infringement under the doctrine of equivalents, but so long as the

functionality of Defender is not expanded to include different passwords for different devices

potential for liability is very low.

The potential for liability based on the examination of similar products is low. The

contacted Paintball Sentry manufacturer implied that he is covered by the prior art in the field.

Based on the patent research and product research, and because as our product stands it simply

contains basic functionality, the Defender is most likely covered under prior art. If the Defender

was to be greatly expanded to contain much more complex and precise methods of functionality,

military products could be examined to find similar products in the field. As the functionality of


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the first implementation of Defender stands, there is little concern for liability based on the

products in the field.

4.5 Summary

Defender’s potential liability was investigated through research of relevant patents and

products in the field. Of particular concern was a patent on an autonomous weapon system that

will require further investigation to ensure a low potential for infringement. A patent on an

implementation of weapon firing safeties was determined to have little reason for liability unless

the functionality of the keypad user input was expanded. Similar products in the field were

determined to be mostly covered under prior art in automated weapon systems. If Defender was

to be expanded to military functionality and precision, methods of implementing more complex

functions and algorithms would need to be further researched. As it stands, the overall potential

for liability in manufacturing the Defender device is low.

5.0 Reliability and Safety Analysis

5.1 Introduction

Defender is a turret-mounted coilgun that uses image processing to control the operation

of the turret-coilgun system, which includes operations such as aiming the turret, charging the

capacitors, and firing the coilgun. The intended function of the Defender project, thus, is to be

able to launch a projectile capable of striking a particular target, a function closely associated to

personal injury. Furthermore, the usage of a coilgun requires implementation of potentially

hazardous circuit elements that present dangers of electrocution and explosion, and software

problems can cause projectiles to be fired unexpectedly. Therefore, the possibilities of harming

users and non-users alike are of the highest criticality, followed by the possibility of elements

overheating and other software errors.

5.2 Reliability Analysis

Four components that are likely to fail are the DRV8821 motor controllers, the

PIC24FJ64GB004 microcontroller, the APT200GN60JDQ4MI-ND IGBT firing controllers, and

the E32D401HPN392MDD0M 400V electrolytic capacitors. The motor microcontrollers are

expected to dissipate a high amount of power at a high temperature and are capable of thermal

shutdown, as specified in the parts reference. This is one of the hotter parts on the board and tied

directly to the aiming of the projectile. The microcontroller is a 44-pin device that directly talks

to two I2C port expanders, the motor controllers, the firing IGBTs, and the atom board, thereby

having complexity through connections and having to run software. The IGBTs are at risk due to

handling high currents and voltages. They are expected to have to handle a 400A pulsing current.

The capacitors are dangerous due to the high voltage they have to handle-400V, and in addition


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have the added danger of being of an uncertain age, increasing the likelihood of them exceeding

their load life expectancy, an event that would lead to less reliable ESR and Capacitance values.

Table 2.1: PIC24FJ64GB004 – Monolithic MOS Digital Microcircuit

λp = (C1πT + C2 πE) πQ πL Failures/106 hours

Parameter

name

Description

Value Comments

C1 Die Complexity .28 MOS, assumption of 1000-

3000 gates

πT Temperature factor .84 TJ = 80 oC (assumed a high

value in range, upper

third)[14]

C2 Package Failure Rate .0235

Nonhermetic SMT,

48 pins

πE Environmental Factor .5 Ground, benign

πQ Quality Factors 10.0 Commercial product

πL Learning Factor 1.0 In production for >2 years

λp Failure Rate 2.4695 * 10-6

Failures/hour

MTTF Mean Time to Failure 404940.27 hrs

= 46.22 yrs

Table 2.2: DRV8821 Monolithic MOS Digital Microcircuit

λp = (C1πT + C2 πE) πQ πL Failures/106 hours

Parameter

name

Description

Value Comments

λb Base Failure Rate .00074

πT Temperature Factor 11 TJ = TC+ɵ JC*P

=35 + 0.22*682

Parameter

name

Description

Value Comments

C1 Die Complexity[12]

.0050 16-bit MOS

Microcontroller[13]

πT Temperature factor .84 TJ = 80 oC (same as

motors), digital MOS

C2 Package Failure Rate .021

Nonhermetic SMT,

44 pins

πE Environmental Factor .5 Ground, benign

πQ Quality Factors 10.0 Commercial product

πL Learning Factor 1.0 In production for >2 years

λp Failure Rate 1.47 * 10 -7

Failures/hour


= 776.57 yrs


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=185.04

πA Application Factor .7 Switching

πR Power Rating Factor 11.18 P = 682[15]

πS Voltage Stress Factor .39 400/600 = .66 ratio

πQ Quality Factor 2.4 Assumed JAN

πE Environmental Factor 1.0 Ground, benign

λp Failure Rate 5.963 * 10 -8

Failures/hour


= 1914.50 yrs

Table 2.3: APT200GN60JDQ4MI-ND Transistor, high power, high frequency, bipolar

λp = λbπTπAπRπSπQπE Failures/106 hours

Parameter

name

Description

Value Comments

TA Ambient Temperature 60 Assumed

λb Base Failure Rate .26 Aluminum, Fixed, 105oC

max rated, Stress = .9 [16]

πCV Capacitance Factor 1.51 C = 3,900 µF

πQ Quality Factor 3.0

Non-established reliability

(do not know age)

πE Environmental Factor 1.0 Ground, benign

λp Failure Rate 1.1778 * 10-6

Failures/hour

MTTF Mean Time to Failure 849040.58 hours

= 96.922 years

Table 2.4: U32D – Electrolytic Aluminum Fixed Capacitor

λp = λbπCV πQ πE Failures/106 hours

Essentially, the motor drivers have the shortest mean time to failure due to high operating

temperature for a device of its complexity, as well as the expectation that we may need them to

go into thermal shutdown in case of high operating temperature. As far as refinement goes,

ambient temperature is a large concern, a concern that can be mitigated with proper heat sinking.

Newer capacitors would be more predictable in behavior. The calculated lifespan for a system

like this is much higher than the market would call for considering the purpose of the device, but

given the dangerous consequences of particular failures, Defender’s reliability should be refined

as much as possible.

5.3 Failure Mode, Effects, and Criticality Analysis (FMECA)

Defender is divided into 3 major subsystems: power and capacitors; the microcontroller

and atom board; and the motors, divided thusly due to their function. The power and capacitor

subsystem consists of the power supplies and their regulators, the transformer, the 400V

capacitors used for the coilgun barrel, and the I2C port expander that controls coilgun charging

and firing. The microcontroller and atom board subsystem consists of the microcontroller, the


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keypad and its encoder, the atom board, the USB connection between the microcontroller and the

atom board, and the connection to the I2C port expander that controls the motors. The motor

subsystem consists of the motors, the motor controllers, and the I2C port expander that interfaces

the microcontroller to the motor controllers. For these subsystems a uniform criticality system is

defined thusly:

Low criticality refers to a failure of some form of intended operation with no

damage to the system or a user. < 10-5

is the acceptable failure rate for this

level.

Medium criticality refers to a failure that causes damage to a part or all of the

system. < 10-7

is the acceptable failure rate for this level.

High criticality refers to a failure that does or can cause potential harm to a user

given proper operation guidelines were followed. Since defender is a projectile

launcher its proper usage can result in injury, an injury that results from misuse

cannot be attributed to a high criticality system failure. The acceptable failure rate

for this level is < 10-9

5.4 Summary

Although Defender is a project designed to provide a measure of security, it is

nonetheless also a system that incorporates a projectile launcher and high-voltage systems. Due

to these attributes, there are numerous failure pathways with Defender that could lead to injury.

Therefore, many safety measures are implemented within the design to mitigate the impact of

such dangers, including fuses and external motor stops. Even with these measures Defender as a

system will require extensive testing, with appropriate safety measures for said tests, to ensure

safe operation. System reliability hinges on software design and operating temperatures.

Software is tested vigorously as it is coded in each stage and operating temperatures can be

mitigated with proper use of heat sinks. Defender is, in the end, inherently a system that requires

special attention to both safety and reliability, and both needs are being tended to with each step

of development.

6.0 Ethical and Environmental Impact Analysis

6.1 Introduction

The Defender turret based defense system is a turret-mounted coil gun that uses image

processing to accurately target specified objects. Defender poses several challenging

environmental and ethical concerns throughout the course of its life-cycle. During the

manufacture phase, the printed circuit boards and various integrated circuits must be synthesized.

During normal use phase, a significant amount of power must be supplied to the turret. Finally,

during the disposal phase, many of the parts on Defender can be easily recycled, while others

must be properly disposed of. All of these concerns must be addressed to assure minimum


-15-

environmental impact during Defender’s life-cycle. On the ethical side, product safety is a huge

concern. The high voltages, moving parts, and high projectile velocities can all lead to user

injury. If it is commercialized, the device must also be properly distributed and tested so that it

is FCC approved.

6.2 Environmental Impact Analysis

The main environmental concerns during the manufacture of Defender are the synthesis

of the printed circuit board (PCB) and the integrated circuits (ICs). Most of the ICs are RoHS

certified[18]

, which means the hazardous chemicals used to synthesize them were limited.

However, there is still a significant negative impact on the environment during their

manufacture. Generation of the PCB is also damaging to the environment because it requires the

use of several poisonous and environmentally dangerous chemicals such as

polytetrafluroethylene (Teflon)[19]

and lead. The amount of hazardous chemicals needed to

produce the PCB and IC’s must be reduced in order minimize the negative effect on the

environment incurred through the manufacturing phase.

Also involved in the manufacture of the turret are several natural resources. These

natural resources are used to create the base of the turret, the coil, the barrel, and the rotator arm.

To create the base of the turret, wide sheets of eighth-inch aluminum are used. To wind the coil,

almost 100 feet of 18 gauge magnet wire is required, and an additional amount of brass and

aluminum is needed for the barrel and rotator arm. All of these metals are in limited supply, and

their production has a negative effect on the environment.

There are several things that can be done to reduce environmental impact during the

manufacture of Defender. To reduce the amount of chemicals used in the synthesis of the PCB

and ICs, the area of the PCB must be minimized as well as the number of ICs required for the

control circuitry. To limit the use of natural resources, the base of the turret will be made as

small as possible, and the coil will be designed such that it requires a minimum amount of

magnet wire.

During the normal use phase of the product’s life-cycle there is little environmental

impact except for power usage. The majority of this power goes to run the Atom board, motors,

and high voltage capacitors. Without charging the capacitors, the system requires 90W to run.

To charge and fire the capacitors, the system requires an additional 1.5 kJ of energy. These

values are relatively high because of the large amount of power needed to run the Atom board

and generate the high voltages required to charge the capacitors. To reduce the energy usage, the

turret has been designed to only charge the capacitors when the system is about to fire, rather

than leave them charged continuously.

The final phase of the life-cycle of Defender is the disposal stage. This is the stage where

the product has become unreliable due to age and must be disassembled and thrown away. There

are many challenges that come with the disposal of Defender because of the toxic nature of many

of its materials, and the large amount of recyclable components. The PCB and ICs are obviously

not biodegradable and must be properly disposed of because they contain lead. All of the


-16-

aluminum, brass, and copper used to make the base, barrel, and coil can be easily recycled.

Also, if they are still functioning properly, the high voltage capacitors and camera can be taken

off and re-used because of their long life times compared to the rest of the system.

To encourage proper disposal of Defender, its distributor will be required to offer a

monetary incentive for the customer to return the product. Once it has been returned, it can be

disassembled and disposed of properly. The PCB and ICs can be taken to a waste disposal

center, all of the parts including the capacitors and camera can be tested and re-used, and all of

the metal can be recycled. This is the best method to minimize the environmental impact of

Defender because it does not require the user to disassemble any parts of Defender.

6.3 Ethical Challenges

There are many ethical challenges facing Defender. The most significant of these are the

plethora of safety issues that come along with building a turret mounted coil gun, which include

high voltages, moving parts, and high speed projectiles. Each of these issues must be addressed

to ensure that no harm comes to the user during normal operation of Defender.

To protect the user from high voltages, warnings will be placed on the base that power

should be completely off before it is opened. Inside the base, there will be several visual

indications if high voltage is present. A red LED controlled by the microcontroller will be on if

the high voltage supply is enabled, and a neon bulb across the high voltage capacitors will glow

if the capacitors are charged. It is not expected that the user will need to open the base of the

turret, but these precautions are still necessary.

The fact that there are moving parts in the design may not seem like a safety issue, but it

turns into one because of the high speed projectile. If there is an error in the code for example,

the motors may move the barrel to a position that may harm the user if the coil were to fire.

Therefore it is necessary to install stoppers on each side of the barrel to limit its range of

movement.

The nature of the coil on the coil gun leads to the possibility that the projectile will be

fired backwards through the barrel rather than forwards. This can happen because the

electromagnetic force applied to the projectile is directed to the center of the coil, and once the

projectile passes the center, the force points backwards. Normally this would only slow the

projectile down, but if the rise time of the voltage pulse is too long, it could cause the projectile

to fire backwards. To prevent this, a metal cap will be welded to the back of the barrel.

Along with the many safety concerns involved in the operation of Defender, there are

also ethical implications involved with its distribution. This product has not been designed for

public use, but if it were to be commercialized, its distribution would need to be controlled just

as the distribution of guns is controlled. To purchase a system, the user would need provide

several forms of identification and submit to a background check.

The electromagnetic interference (EMI) that is induced by the high voltage LC pulser on

the coil gun is also a significant ethical concern. If Defender is operating in close proximity to

other electronics, there is a possibility that any EMI given off when it fires could damage or


-17-

destroy the electronics. Therefore it is important that the LC circuit be properly shielded to

prevent damage. If this product were to become commercialized, it would need to be verified by

the FCC before it could go into production.

6.4 Summary

The Defender turret defense system poses many challenging environmental and ethical

problems. During its life-cycle, the system must be properly manufactured, operated, and

disposed of in order to minimize its environmental impact. Of these phases, the disposal phase is

the most important because it is here that the parts are recycled or properly disposed of. In order

to protect the user, there are many safety precautions that must be made to protect against high

voltages, moving parts, and high velocity projectiles. Warnings will be placed on the base, and

stoppers will be used to prevent unwanted rotation of the barrel. The system will be shielded to

minimize the effects of EMI, and if commercialized, a background check will be required in

order to purchase the Defender system.

7.0 Packaging Design Considerations

7.1 Introduction

The Defender turret based defense system consists of four major physical components:

the base, the rotator, the coil gun, and the camera. The base is a divided metal box which houses

all of the critical control components along with the high voltage capacitors. The coil gun is

mounted on top of the rotator, and the rotator is mounted on top of the metal box. Stepper

motors in the rotator allow the coil gun to be directed at certain targets. The camera will be

mounted on the metal box because it has its own panning abilities. An Atom board and a

microcontroller are located on one side of the metal box and act as the controls for the coil gun,

the camera, and the stepper motors. The other side of the divided metal box houses the high

voltage capacitors. The purpose of the packaging design is to minimize EMI (Electromagnetic

Interference), and allow the Defender to be easily mounted.

7.2.0 Commercial Product Packaging

Due to the military nature of the coil gun and the turret, it is very difficult to find similar

commercial products. However, one hobbyist was found who sells motion-tracking turrets

similar to what the Defender design.[20]

A very expensive vehicle-mounted turret designed for

Armored Personnel Carriers was also found.[21]

7.2.1 Product #1: Sentry Project Turret

System

One product that is similar to the turret

design of the Defender is the Sentry Project Turret

System. Positive aspects of the Sentry Project


-18-

include an ability to interface with any trigger controlled gun, semi to full auto firing, movement

detection, automated firing, portability, and a comprehensive GUI system. Negative aspects

include that the camera must be stationary in order to operate, and a coil gun cannot be interfaced

with the turret. The Defender will have a turret stage similar to the Sentry Turret. However, the

turret will be mounted on top of the box instead of to the side, and there will be no tripod

attached to the base. The base will also be much larger.

7.2.2 Product #2: Tactical Remote Turret

A second product that resembles the Defender

system is the TRT-25MM, or the Tactical Remote Turret

(TRT). Positive aspects of the TRT include adaptability

to a number of different weapons, ability to operate

during the day or at night, operable while moving,

simple user interface, and light-weight (compared to that

of the vehicle). Negative aspects include that it is very

expensive and not capable of interfacing with a coil gun.

The Defender packaging design will be very different

from the TRT because its turret is designed to be mounted indoors, and will not need to be

armored to the extent of the TRT. However, the camera will be mounted beneath the barrel,

similar to the TRT design.

7.3 Project Packaging Specifications

There are three major packaging design constraints for Defender. The first is portability,

which is required because future iterations of Defender will be ceiling mountable. This requires

that it be relatively compact and lightweight. The second is EMI effects from the coil gun,

which may damage certain sensitive control circuitry. The third is high voltage safety

precautions, which arise from the high voltage required to fire the coil gun.

To make Defender compact, PCBs and base have been designed to minimize the amount

of unused space. The atom board and the high voltage capacitors take up the majority of the real

estate inside the base. The rest of the space is taken up by the stepper motor and the PCBs. The

length of the Rotator will be minimized to the extent that the coil gun has the maximum degrees

of freedom. Since this is the first iteration of Defender, portability will not be prioritized.

To reduce EMI effects, the base section of the turret will be physically divided into two

components. One compartment will contain all of the circuitry which is sensitive to EMI (PCB

1) and the other will contain all high voltage components (PCB 2). The metal box will act as a

Faraday cage and reduce the EMI from the capacitors while simultaneously protecting the

sensitive circuitry. The coil on the coil gun will also be wound with copper tape, and bypass

capacitors will be used generously on the PCBs. Shielded cable will be used for all interfacing.

To protect the circuitry and the user from high voltages, all capacitors and the voltage

multiplier circuit will be insulated with polycarbonate. In addition, a physical kill switch will be


-19-

placed outside the base, and an LED will be turned on whenever high voltages are present. To

protect the circuitry, optical isolators will be placed at every connection to high voltages.

The dimensions of the base are 350mm x 600mm x 100mm. This houses the high

voltage capacitors, which have a diameter of 63.5 mm and a height of 130.18 mm. The Primary

Control PCB has dimensions of 170 mm x 85mm and the Capacitor Control PCB has dimensions

of 100 mm x 75 mm. There are two Lazy Susans, one located on top of the base and one on the

top of the rotator. The larger one on the top of the base is 152.4 mm x 152.4 mm, and the other

smaller one is 76.2mm x 76.2 mm. The barrel for the coil gun is 20mm in diameter and 400mm

in length. These dimensions may change if a metal box is found that can be ordered instead of

custom made, or if hardware is added or changed.

7.4 PCB Footprint Layout

To encourage portability the PCBs will need to be relatively compact. Two PCBs were

designed because one PCB is needed for each side of the divided box. Therefore, one PCB will

handle control of the capacitors charging and discharging, and the other will handle control of

the power supply, the stepper motors, and the firing. Most of the major components, including

the primary microcontroller, stepper motor microcontroller, voltage regulators, and transformer

will be contained on the second PCB. Because of the inherent high voltages in the transformer,

it will be well separated from the microcontrollers on the PCB.

The estimated size of the capacitor charging and discharging PCB is 0.16m by 0.08m

and the estimated size of the primary control PCB is 300 mm by 150 mm. Most of the area on

the first PCB will be taken up by a high voltage transformer and its associated resistors and

capacitors. The area on the second PCB will be taken up primarily by the power supply

components, which include the transformer and its associated circuitry. The microcontrollers

and their associated peripheral resistors and capacitors will take up the majority of the remaining

space. The purpose of having two PCBs is to shield the control circuitry from the EMI of the

coil gun and capacitors.

7.5 Summary

There are three major design constraints for Defender: portability, EMI protection, and

high voltage precautions. Portability will not be optimized since this is the first iteration of

Defender. EMI will be reduced by containing sensitive circuitry within a metal box, applying

copper tape to the coil gun, and using bypass capacitors on the PCBs. A physical kill switch will

be mounted on the outside of the base in case of emergency, and proper discharge circuitry will

be used in combination with the high voltage capacitors and the voltage multiplier. The physical

design will be similar to the Sentry Project Turret System in that it will use a Rotator arm to

direct the coil gun, and a camera to target moving objects. However, the turret will not be

mounted on a tripod and the base will be much larger to accommodate the capacitors and

circuitry needed for the coil gun.


-20-

8.0 Schematic Design Considerations

8.1 Introduction

The Defender is a turret based defense system. The system will search for targets, charge

capacitors to a high voltage, and utilize electromagnetic force to propel a projectile toward the

target. The system will be divided between two printed circuit boards, with the high voltage

system being on a separate printed circuit board from the low voltage components. This

implementation was chosen because optical isolation will be utilized on communications

between these two circuit boards in order to safeguard against any malfunctions. An Inter-

Integrated Circuit (I2C) bus is implemented as the main communication network between the

microcontroller and the circuit. Along with component protection, the system is also

implemented with user safety in mind. The high voltage capacitor circuitry is implemented such

that the high voltage capacitors will unable to overcharge and can be slowly discharged safely

over time without any danger to the user. For the purposes of analysis, the system will be

grouped into the main operating subsystems of high voltage power supply, capacitor bank, motor

devices, microcontroller circuitry, and Atom processor devices. A finalized block diagram is

included in section 1.0 and finalized circuit schematics are available in appendix C.

8.2 Theory of Operation

Defender consists of numerous subsystems with various power and communication

demands. The system will be powered through a wall wart in order to achieve the high voltages

necessary for the system. Defender also requires multiple power levels for circuitry and devices.

Power Supply Requirements:

3.3 Volts Master Microcontroller

12 Volts Motors, Atom Processor

360 VRMS Capacitor Charging Circuit

The high voltage power supply system is implemented in order to provide the necessary

voltage level to charge the coilgun capacitors. This system consists of a transformer and a full-

bridge wave rectifier producing a high voltage of around 360 VRMS or a peak of 510 volts. A

current limiting resistor is placed in the circuit to prevent large inrush currents. The capacitors[22]

available to the team are rated for 400 volts, so the high voltage system is designed with respect

to this constraint. The varying power supply requirements elicit the need for thorough design

considerations for a successful implementation.

Control circuitry is implemented in order to disable charging and prevent the capacitors

from being charged over 400 volts. The circuit contains a microcontroller controlled power

enable switch in order to allow the capacitors to begin charging. While the system is charging,

the voltage across the capacitors is measured by reduction through a voltage divider, conversion

with an analog to digital converter, and communication to the microcontroller over the I2C


-21-

network. Once a pre-determined threshold voltage is met, the microcontroller will disable the

charging circuit. This threshold will not be precise until the circuit is tested under its operating

conditions involving loss. This control circuitry is an integral part of the software controlled

operation of the system.

The capacitor bank system consists of a slow discharge mode and a firing mode. Once

the capacitors are charged by the high voltage system, a microcontroller controlled switch will

enable them to slowly discharge through the circuitry over a period of time if necessary. The

firing circuit consists of the single-stage coil and an Insulated-gate bipolar transistor (IGBT.)

The chassis mounted IGBT[23]

is rated for a VCE of 600 volts in order to support the design’s high

voltage requirement. If the coilgun is to be fired, the microcontroller will enable the IGBT to

trigger a powerful, short electromagnetic pulse from the capacitors through the coil to propel the

projectile out of the barrel. The barrel is made of brass in order to provide low friction. Upon

the projectile being fired, the IGBT must be promptly turned off as the projectile reaches half the

length of the coil or else the projectile begins experiencing force in the opposite direction. A

photodiode system is implemented along the barrel in order to monitor projectile position and

velocity. The photodiodes signal the microcontroller as the projectile passes, and the

microcontroller disables the IGBT. The circuit will also have a manual kill switch in case of any

microcontroller malfunctions in testing.

The motor system will consist of two 12 volt stepper motors attached by direct drive to

turn two Lazy Susan stages in the azimuth and elevation planes. The 12 volt motors were

preferred due to the fact that the Atom processor and the camera motors are also operating on 12

volts. The barrel will be thin and lightweight, so 12 volt motors will be sufficient to turn the

system. A dedicated H-bridge controller[24]

is implemented to control both motors with

commands coming from an I2C port expansion. The system will implement one port expansion

for both motors such that both motors can be stepped with a single command. The motor

system will be capable of microstepping for smooth operation. Motor positions will be

calculated from the number of steps taken in order to analyze system position along with the

image processing data. The motors will be receiving commands from the microcontroller.

The PIC24[25]

microcontroller device, powered by 3.3 volts, serves as the communication

center for the system. Information will be gathered and sent over the system through an I2C bus.

The I2C network will be operating at the fast mode 400 kHz operating frequency. The fast mode

speed will be fast enough to suit needs of the system. The circuit firing time requires an

accuracy of around 0.1 milliseconds in order to stop the circuit when the projectile is halfway

through the coil, and this fast speed should sufficiently allow for that. The I2C bus will supply

information to two port expansions. The first port expansion will contain information for the

high voltage and capacitor systems. This expansion will contain optical isolation to protect the

low voltage system components from any malfunctioning circuitry. The second expansion will

be used to control the motors. The microcontroller will also support a keypad encoder to collect

user identification codes. The keypad will collect user identification data required in order to

gain access to the system. The Atom processor will be providing system commands to the


-22-

microcontroller through a USB connection. Data regarding the state of charging, firing, and

motors will be collected by the microcontroller to be sent to the Atom processor.

The Intel Atom processor powered by 12 volts will be the processing center for the

system. Commands will be sent to the microcontroller over USB, and information will be

received to be processed to determine further commands. A Pan-Tilt-Zoom camera[26]

will be

connected to the Atom by USB and powered by 12 volts in order to perform image processing

for target recognition and tracking. The processed images will determine where and when to aim

and fire based on the camera images, camera motor positions, and turret motor positions. Audio

warnings will be produced through a USB speaker set interfaced to the board. A personal

computer based user interface will be implemented through an Ethernet connection in order to

allow user control from a safe distance.

8.3 Hardware Design Narrative

Beyond any basic timers and interrupts, the microcontroller will be primarily utilizing I2C

and USB. The port pins are mandated by the microcontroller, so they will be used as required.

I2C was chosen as the primary communication bus in order to provide adaptability in the design.

The I2C network was also chosen due to the large amount of I

2C compatible parts available to the

design. The I2C network allows the microcontroller to function as the communication center

between the circuit and the Atom processor. The Atom processor will send and receive data over

USB to the microcontroller in order to calculate the system state and issue commands.

The microcontroller will be collecting data from numerous sources. A keypad encoder

will be implemented through the Parallel Master Port or the UART in order to collect user

identification data. Other data to be collected includes capacitor voltage and photodiode

information. The microcontroller will also be sending various signals over I2C to various

destinations in the high voltage circuitry. These signals include a high voltage charging switch, a

high voltage discharge switch, and a firing switch. The microcontroller is required to

communicate with the high voltage system, so any signals to and from the high voltage system

will all be optically isolated in order to protect the system from any high voltage. The

microcontroller will also control the motors of the turret through the same I2C network. The

system is configured to implement one port expansion for both motors in order to allow stepping

with a single command. The high voltage system and the motor system will be implemented

through separate port expansions on the same I2C network.

8.4 Summary

The defender system consists of a high voltage power supply, a capacitor bank, motor

devices, microcontroller circuitry, and an Atom processor. At the top level of command, the

Atom processor will be issuing the system commands to the microcontroller. The

microcontroller sends these commands over the I2C data bus, and it collects information to be

returned to the Atom. The I2C data bus implementation is utilized to provide adaptability in

monitoring and commanding the high voltage systems and the motors. Optical isolation will be


-23-

utilized when communicating with the high voltage system in order to ensure that any possible

malfunctions errors in testing are contained. The Defender system is designed to provide an

adaptable, safe implementation to propelling a projectile towards a target.

9.0 PCB Layout Design Considerations

9.1 Introduction

Defender is a coilgun based turret defense system. There are two PCBs that comprise the

surface mount components of Defender: a high voltage power board and a separate board for all

communication and control. The high voltage board comprises of a rectifier circuit for charging a

capacitor bank to 400V, a safety discharge circuit for this bank, and the ability to discharge this

bank through the coilgun. Also present on this board are another transformer and two other

rectifiers for the low voltage systems on the control board. The main control board talks to the

power board through an optically isolated I2C bus. On the main board there are two power

supplies: one at 3.3V for the microcontroller and all other components and one at 12V for the

atom board and motors. The microcontroller interfaces through an I2C bus to a variety of

components, such as the motor controller, a keypad encoder, and the I2C port expander on the

power board. A USB connection to the atom board is also present.

9.2 PCB Layout Design Considerations - Overall

The current size of our boards is 170mm x 85mm and 100mm x 75mm which comes out

to 34 in2 of area. The size of these boards leaves more than enough room for component

placement and signal routing as shown in Appendix B. The only limitations with large parts are

the power supply components, such as large filter capacitors and inductors. On the

communication and control board most signal traces will be 12 mils in width following the

recommendations from the lecture. The exception to this is the motor to connector traces which

will be handling higher currents and voltages (.4A at 12V) as well as some of the power supply

traces as discussed in section 4.0. The trace width on the power board is not as critical as the

trace spacing to avoid discharge of voltage along the board. The maximum current flowing

through any power board trace should be less than 500mA. According to table 6-1 in IPC2221[27]

the spacing for a coated board such as ours needs to be at least 1.5mm (60 mils) for the 500V

peak DC voltage. The high current pulse of 400A that goes through the coilgun is too high for

any simple PCB trace so we are moving all the components that this current goes through off

board.

Signal routing is simplified greatly by the presence of the I2C bus. All peripherals except

for the external phototransistors are connected to this bus either directly or through the use of an

I2C 16 pin port expander. These port expanders are positioned closely to the part they are

controlling for short traces and simple routing. The phototransistors will have direct routing to

the microcontroller pins through an external header and some ESD protection circuitry.


-24-

There are a few manufacturing concerns for soldering a few parts that need to be

addressed. Several parts, such as the motor controller and power supplies, have thermal pads that

will be soldered using vias underneath the pad. The keypad encoder is an extremely small QFN

package that could be difficult to solder and could very easily be done incorrectly with no easy

way to remove the part. To solve this there will actually be two spots for the keypad to encoder

to be soldered to on the chance that pads are destroyed. Thermal management of some parts is an

issue as well. Parts which will be generating large amounts of heat will have large (>.5 in2)

copper pours to act as heatsinks. Where possible these heatsinks will be linked directly to the

ground plane, as in the case of the motor controller[28]

. These heatsinks will be placed as far

away from other components as the design allows to avoid thermal effects on other components.

EMI on the power board is a large concern with the voltage and switching levels present.

The components on the power board such as the ADC’s will have input filters associated with

their input resistors to reduce high frequency noise. The I/O port expander on this board is for

digital switching of MOSFETs only and will not be easily affected by EMI. The filter capacitors

for the rectifier networks are placed on the communication boards separate from the power

boards to also reduce this EMI. The 45° trace rule will be observed to reduce reflections and

radiated noise as much as possible. Bypass capacitors are present on every power connection to

an IC and both the 12V and the 3.3V supply have their own bulk capacitors.

9.3 PCB Layout Design Considerations - Microcontroller

The microcontroller, a PIC24FJ64GB004, is being used primarily as a communication

router and translator in our design. It will take signals in from a USB line and send them out to

the correct I2C bus. The I

2C bus requires external pull-up resistors and the USB bus also require

some special layout measures; these are described in the datasheet[29]

. None of the more

complicated functions of the microcontroller are being utilized, such as an external oscillator,

and we do not need to take any particularly detailed precautions on the PCB layout around the

microcontroller due to this fact. All bypass capacitors will be located very close to the multiple

Vdd/Vss pin pairs of the micro according to the datasheet[29]

. A special header for In-Circuit

Debugging (ICD) will be routed to allow for easier programming and debugging. Any micro pin

that is routed to an outside header such as those for ICD or those associated with external input

will have a small (<470Ω) resistor to reduce the chances of ESD damage. Care will have to be

taken with the circuit associated with MCLR input. This input needs to have a filter and switch

associated with it as well as clear from any noise sources as to avoid spurious resets. The 3.3V

power rail is a fairly low current rail (<100mA) and have a trace width of 40mils for the majority

of the board, narrowing only to get to the port pins they are required. The 12V rail has a much

higher current load, up to 3.5A, therefore it has a trace width of 100mils wherever possible.

9.4 PCB Layout Design Considerations - Power Supply

There are three power supplies in Defender: a high voltage AC to DC charging system

for the capacitor bank, a 3.3V rail for logic, and a 12V rail for the motors and the Atom board.


-25-

The communication and control board will utilize a ground plane for all digital and control logic.

The power board will not have a ground plane since most of the signals that are grounded are

high voltage AC signals and separating the grounds from the digital logic will reduce noise. The

3.3V regulator is the simplest to route traces.

The 3.3V rail is a LDO regulator from National Semiconductor, the LP3872EMP-3.3[30]

.

This chip has no special considerations other than closely placing the input filter capacitor from

the rectifier and the output tank capacitor close to the chip. The 3.3V rail will be powering

mostly digital components and will be connected to the ground plane to reduce noise. The few

analog components, such as voltage references and ADCs, will have a separate power rail from

the digital components. This chip does require a large copper area beneath the ground tab for

heatsinking.

The 12V supply is a switching power supply also from National Semiconductor, the

LM2677S-12[31]

. This switching power supply has a more complicated layout pattern than the

LDO regulator with more requirements on which components need to be closest. These

guidelines are detailed out in National Semiconductor AN-1229[32]

. These guidelines can be best

summarized with having traces that carry switching currents be as short as possible to reduce

inductance and therefore voltage spikes. The placement of the inductor, catch diode, and large

input capacitor are the most critical parts and will be placed first. The 12V rail powers two main

components: the Atom board and the motor controller. These devices will each have their own

power rail going to a star point at the 12V input. The same ground plane as the 3.3V rail will be

utilized under the assumption that the ground plane is not a source of noise, although separate

ground rails can be utilized if this is a concern.

The high voltage power supply on the power board uses a chassis mount transformer to

step up the AC voltage to 360V rms and then rectify onboard to produce a charging voltage. The

critical parameter here is trace clearance as discussed in section 2.0 to avoid discharging across

the board. The clearance between each trace needs to be at least 1.5mils. The ground rail for this

supply will be isolated from the other grounds of the system. The traces for anything carrying

these high voltages will need to be as wide and short as possible to reduce resistance and

inductance. We want to place these connections at the edge of the board to avoid having wire

carrying the high voltage close to the board and possibly inducing EMI.

9.5 Summary

The overall PCB structure of Defender was presented in its current two board form. Each

board has its own complications to be considered in laying out the PCB. Issues such as trace

width and clearance, component placement, thermal management, EMI reduction, bypass

capacitor placement, ground plane and power routing, and high voltage isolation are looked at.

The microcontroller routing was examined and it was found that no special considerations must

be taken other than those standard in the data sheet. The layouts required for the various power

supplies were also examined, taking into account more variables such as trace clearance, ground

plane routing, and star point construction of the power rails.


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10.0 Software Design Considerations

10.1 Introduction

Defender is a turret-mounted coilgun that uses image processing to control the operation

of the turret-coilgun system, which includes operations such as aiming the turret, charging the

capacitors, and firing the coilgun. The software is mainly written on three different systems—A

GUI is written in Java to be run on any computer, the image processing code is put on the

embedded processor for determining and tracking targets, and encoding and decoding for I2C

buses will be performed on the PIC24 family microcontroller. Between all three interfaces code

is written to facilitate communication.

10.2 Software Design Considerations

10.2.1 I2C Pins – Expander Interface

All of the control signals sent out from the control microcontroller use the I2C Pin SDA1

for output. A port expander is tied to this pin on the microcontroller to send the proper signals to

each individual controlled component, and the signal itself will select the target being controlled

by activating a particular output on the port expander. To use this module on the microcontroller,

the I2CENand DISSLW bit must be initiated high on register I2C1CON, enabling the module

and disabling slew rate control, with all other bits initiated low.

10.2.2 UART1 - Keypad

The Keypad also makes use of the UART interface on the PIC24. The keypad sends data

into the microcontroller, so UART1’s Rx pin is necessary for this interchange. Pin RC3 will be

used for input, and initialization of UART1 will require setting UARTEN high in U1MODE,

with all other bits in U1MODE being set low and all bits in U1STA being set low.

10.2.3 USB

The PIC24F micro will be configured as a USB Device, eschewing host mode

functionality, as the Atom board will be the USB host, using its USB Module, with the

embedded processor acting as a USB host. In device mode, the Rx pins will be used for output to

the atom board, while the Tx pins will be used for input. To enable device mode, PPBRST on

U1CON will be disabled, then all interrupts will be disabled by setting U1IE and U1EIE to 00h.

All existing interrupt flags will be cleared by setting U1IR and U1EIR to FFh. Then the USB

Module will be enabled by setting USBEN bit on U1CON high. Then the endpoint zero buffer

will be set to receive the first setup packet through setting EPRXEN and EPHSHK bits to 1 on

U1EP0. The USB module is powered up by setting USBPWR bit on U1PWRC, and the D+ pull-

up resistor is enabled by setting DPPULUP on U1OTGCON.

10.2.4 Application Code Organization

Application code for Defender is written partly in Java using the Eclipse Helios IDE and

partly in C++ using Visual Studio 2008. These executables are located on different machines and


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communicate through a common medium of Ethernet packets. Manual operation mode is

interrupt-driven on both the GUI machine and the embedded processor, as each user input sets

off action handlers which then set off functions on the embedded processor. Automatic mode

operation on the embedded processor is a polling loop that repeatedly takes in image data, and all

action handlers save the mode selection are disabled on the GUI itself, as it enters a polling loop

to receive status updates from the embedded processor. The microcontroller’s software will be

interrupt driven so as to wait for instructions from the embedded processor, which may be sent

out at irregular intervals.

10.2.5 Debugging Provisions

As far as debugging goes, all modules used in defender are highly functionalized, and

debug versions of the functions can be created easily by calling a particular function at a point

closer to where the result is needed. For example, offline packet dump files are used to test

particular packet captures without the need to have a live connection between devices. The

overall approach will be to use manual mode operation to ensure outside control of the turret

itself, and then automatic operation mode will generate instructions using the same

specifications.

10.2.6 Memory Map (PIC24F)

LSB Address Space

0000h – 07FEh SFR Space

0800h – 1FFEh Main Code Area

2000h – 7FFEh Data Storage

10.3 Software Design Narrative

10.3.1 GUI GUIMain.java GUI.java

The entry point into the code for the GUI portion is the main(string[] args) function on

GUIMain.java, a wrapper class that invokes the init() method of the GUI.java class, ensures

graceful exits, and handles inbound packets. This initialization call initiates all swing

components of the GUI, creates all the action handlers, and sets up the packet handlers that will

handle communication. Upon initialization, the program is set to manual mode operation. GUI

action events are tied to send packet functions in order to give the embedded processor

commands.

Status: Written, tested, fully functional, awaiting integration.

10.3.2 Packet Capture

The packet handlers for the Java code are objects from the jnetpcap library instantiated

to send and receive packets over a particular network device, and two pcap streams are opened—

a sender by the GUI itself and a receiver by the wrapper class for the GUI. For the C++ side of

the code, packet handler objects are created from the winpcap library and used in a similar

fashion to the packet handlers in the GUI, being set to a particular network device, one connected

http://engineering.purdue.edu/477grp6/docs/code/GUIMain.java

http://engineering.purdue.edu/477grp6/docs/code/GUI.java


-28-

to the GUI software. Send and receive functions are based on sends and receives native to these

packet handlers, but are modified to handle string data for integration into code, as packet

contents are used to control program flow. A set of packets are also used for image transfer, with

instructions to open, write, and close a file pointer to ensure proper transfer. Receive methods

also filter packets by data contents to ensure proper instructions are read, as an unexpected

packet being interpreted as ―fire‖ would certainly violate many safety concerns for the project.

Status: Written, tested, fully functional, awaiting integration.

10.3.3 Wrapper for Atom Board software

The software bundle on the atom board is initialized by a main() function that will

initialize operation mode to manual mode and set up a loop to receive packets from the GUI.

Packet receipt is tied into calling other functions wrapped into the main() function, and the

software exits upon receiving a ―kill‖ packet from the GUI itself. When automatic mode is

invoked through a packet on the GUI, functions from the image processing library are called at

regular intervals to perform the processing. To send messages to the microcontroller, functions

using the USB libraries are configured to send particular messages. Furthermore, the wrapper has

the ability to load images from the camera and transfer them using packet sending protocol on

request by the GUI, which then displays them.

Status: Written, tested, fully functional.

10.3.4 Image Processing 477CameraRoutines.cpp

The image processing module contains many functions that correspond to the actions of

image processing, with each key step tied to its own function. The SetupVI and CreateImage

functions are entry point functions that establish the video input and image objects used further

in the program. The separate function is used on an image to generate regions. ThresholdYellow

generates binary thresholding based on the hue component of a pixel value, but can be modified

to work for other colors too. Morphology then removes the noise from the map generated by

ThresholdYellow. The findArea function then finds the area in pixels of each region, this

function is called by pickRegion in order to find the largest region on the image. The centroid

function finds the centroid of a particular set of points, which correspond to a region, and the

axes function takes a centroid on a particular image and finds the axes of the region

corresponding to that centroid. The calcZ function finds the distance to a region in pixels using

major axis length in pixels and the known size of the object in centimeters. CalcXYZ uses the

distance found in calcZ to find the X and Y locations in centimeters. All of these methods are

wrapped into the LocateObject method.

Status: Written, tested, fully functional, awaiting parameterization and integration.

10.3.5 Microcontroller Instruction Encoding

The microcontroller has one main polling loop for USB instructions, with two interrupts

that set off flags that will cause other behavior within the main polling loop. Every 10

milliseconds the I2C line that is associated with a port expander leading to an ADC is read to

ensure the capacitors do not overcharge and also returns a USB packet containing the ADC value

to be displayed on the GUI, while the barrel photosensor interrupts are constantly checked to

http://engineering.purdue.edu/477grp6/docs/code/477CameraRoutines.cpp


-29-

ensure that firing goes off smoothly. Upon reception of a USB instruction, that instruction is

translated into a motor or capacitor charging function. There is a set of startup routines that

configure the I2C port expanders by setting their slave addresses and the PWMs that drive the

motors, as well as move the motors around and wait for a set of photosensor interrupts to find the

origin for camera synchronization.

Status: Written, tested, functional.

10.4.0 Summary

The software architecture and design functionality of all the modules of Defender were

reviewed, and the interconnectivity between the GUI, Ethernet libraries, and Image processing

was discussed, as well as intricacies to the function to each part. A plan of execution for PIC24F-

related code was offered and the mechanics of said code were discussed, albeit not enumerated.

Essentially, all work done so far toward the software portions of Defender have been related in

brief in this report.

11.0 Version 2 Changes

Team Defender learned much from the completion of the project. The most important

realization is that projects should always be started yesterday. While the project can be deemed

successful in satisfying criteria established for completion goals, there are functionalities that

could have been added, provided additional time, which would have greatly improved the

performance of the project.

For a second iteration of Defender, there are several modifications that could have been

made to improve its hardware implementation. The speed of the projectile could have been

vastly improved by slotting the barrel or implementing a multistage coilgun. By slotting the

barrel, eddy currents in the barrel would be reduced, which would increase the amount of energy

transferred to the projectile. Implementing a multistage coilgun would have a similar effect.

Multiple coils would be aligned along the barrel and pulsed individually as the projectile passes

through each. This would add more energy to the projectile as it passes through the barrel. The

aluminum box and arm both turned out as we expected, but assembly of this apparatus is a

lengthy and costly process. More time should have been spent planning how the packaging

should fit together.

The team learned much about printed circuit board prototyping. It was learned that

virtually every important pin should wired to a header for debugging purposes. Furthermore,

wiring the shutdown pin on power supplies, especially switching power supplies, is very

important since those supplies do not operate properly if no load is attached to them and

therefore should only be turned on when a load is present. Our I2C line is particularly noisy,

likely because we do not have any bypass capacitors on this line and while the noise is not

currently an issue it could be in the future. Lastly, QFN parts, while simpler to implement than

the alternative, should be avoided as they are difficult to replace if damaged.


-30-

In the future, consideration will be made to learn to compile a Windows executable in

Linux. Programmers in the field have given advice that many of the notorious Visual Studio

compilation errors would never occur on Linux. One trade-off in using Linux is that the learning

curve is much higher. Another trade-off is that many sample codes provided are often only

implemented in Visual Studio. A third problem with Linux is the lack of universal support for

device drivers. The benefit would be that once mastered, frequent configuration errors would not

provide such a problem. While it seems to be an inevitable necessity to learn to operate in the

Visual Studio programming environment, investigating other ways to implement software

functionality would be a useful investment towards future coding projects. Unfortunately, the

only way to learn to use Visual Studio effectively seems to be through lengthy debugging

procedures.

12.0 Summary and Conclusions

The team’s major software accomplishments include Ethernet communication between a

Java user interface and a C++ executable, USB Communication between a C++ executable and a

microcontroller, and I2C communication between a microcontroller and its devices. This

extensive software network provides an interchange of commands and information between the

user and the Defender system. Along with this network, the system also utilizes camera based

target recognition and tracking through C++ image processing libraries.

In implementing the software network, the team learned to effectively coordinate

production of a multilayer code hierarchy. Three members on the team worked on various

portions of the software concurrently, and much communication was necessary in order to

prepare the code to be integrated together. Through an arduous debugging procedure, the team

also learned much of the USB device enumeration process and protocol.

The major hardware accomplishments include a high voltage capacitor circuit capable of

charging, discharging, and firing. The firing system pulses current quickly through a coil to

generate a strong magnetic field which propels a projectile at high speeds. Along with this, the

system is able to control turret motion along two axes through the use of software-controlled

stepper motors. A custom-made enclosure was machined to contain all the electronics as well as

the motor mounts.

Through working on this project, the team learned about high voltage power system

design, coilgun design, printed circuit board design, soldering techniques, Ethernet packet

transfer, USB microcontroller communication, Microsoft Visual Studio utilization, and

numerous methods of debugging the aforementioned. More specific development techniques

acquired through working on this project include the importance of wiring all reset and shutdown

pins, being aware of the configuration tribulations associated with using Visual Studio to develop

any part of a software project, the ability to analyze code provided for particular modules and

adapt it to suit the project’s needs, and the versatility of flywiring to fix circuit flaws.


-31-

13.0 References

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http://www.usa.canon.com/cusa/consumer/products/security_video_solutions/analog_pa

n_tilt_zoom_video_cameras/vc_c50i_vc_c50ir. [Accessed: Feb 3, 2011].

[2] BAE Systems. TRT-25MM Tactical Remote Turret [Online]. Available:

http://www.baesystems.com/ProductsServices/bae_prod_trt25mm.html. [Accessed: Feb

5, 2011].

[3] Panhard. WASP [Online]. Available: http://www.panhard.fr/anglais/index.htm .

[Accessed: Feb 5, 2011].

[4] Andrew Chuter. Unmanned Turrets Spur Market Surge [Online]. Available:

http://www.defensenews.com/story.php?i=4677659 . [Accessed: Feb 5, 2011].

[5] Microchip. PIC24FJ64GB004 [Online]. Available:

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en536118.


[6] EMCO. Regulated, Programmable 15 Watt HV Modules [Online]. Available:

http://www.emcohighvoltage.com/pdfs/hseries.pdf. [Accessed: Feb 6,2011].

[7] Texas Instruments. Dual Stepper Motor Controller/Driver [Online]. Available:

http://focus.ti.com/docs/prod/folders/print/drv8821.html. [Accessed: Feb 4, 2011].

[8] Microsemi. APT200GN60JDQ4 [Online]. Available:

http://www.microsemi.com/datasheets/200GN60JDQ4_B.PDF [Accessed Feb 5,2011].

[9] FreePatentsOnline. Autonomous Weapon System [Online]. Available:

http://www.freepatentsonline.com/7210392.html. [Accessed Mar 27,2011]

[10] FreePatentsOnline. Weapons firing safeties and methods of operating the same

[Online]. Available: http://www.freepatentsonline.com/7600339.html. [Accessed Mar

27,2011].

[11] The Sentry Project. Paintball/Airsoft Sentry [Online]. Available:

http://www.paintballsentry.com/Products.htm. [Accessed Mar 28,2011].

[12] United States Department of Defense, Military Handbook on Reliability Prediction of

Electronic Equipment. [Online]. Available:

https://engineering.purdue.edu/ece477/Homework/CommonRefs/Mil-Hdbk-217F.pdf.

[Accessed: April 7, 2011].

http://www.usa.canon.com/cusa/consumer/products/security_video_solutions/analog_pan_tilt_zoom_video_cameras/vc_c50i_vc_c50ir


http://www.baesystems.com/ProductsServices/bae_prod_trt25mm.html

http://www.panhard.fr/anglais/index.htm

http://www.defensenews.com/story.php?i=4677659

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en536118

http://www.emcohighvoltage.com/pdfs/hseries.pdf

http://focus.ti.com/docs/prod/folders/print/drv8821.html

http://www.microsemi.com/datasheets/200GN60JDQ4_B.PDF

http://www.freepatentsonline.com/7210392.html

http://www.freepatentsonline.com/7600339.html

http://www.paintballsentry.com/Products.htm

https://engineering.purdue.edu/ece477/Homework/CommonRefs/Mil-Hdbk-217F.pdf


-32-

[13] Microchip, PIC24FJ64GB004 Family Data Sheet. [Online] Available:

http://ww1.microchip.com/downloads/en/DeviceDoc/39940d.pdf [Accessed: April 7,

2011].


http://focus.ti.com/docs/prod/folders/print/drv8821.html. [Accessed: April 7, 2011].


http://www.microsemi.com/datasheets/200GN60JDQ4_B.PDF [Accessed April

7,2011].

[16] United Chemi-Con, U32D series. [Online] Available: http://www.chemi-

con.com/files/U32D_Web.pdf [Accessed: April 7, 2011].

[17] Frank G. Splitt, ―Engineering Education Reform: A Trilogy‖ IEC, 2003 [Online]

Available:

https://engineering.purdue.edu/ece477/Homework/CommonRefs/enviro_refs.pdf

[Accessed April 14, 2011].

[18] Wikipedia, ―Restriction of Hazardous Substance Directive,‖ 2011 [Online] Available:

http://en.wikipedia.org/wiki/RoHS [Accessed April 14, 2011].

[19] Wikipedia, ―Polytetrafluroethylene,‖ 2011 [Online] Available:

http://en.wikipedia.org/wiki/Polytetrafluroethylene [Accessed April 14, 2011].

[20] The Sentry Project. Sentry Turret System [Online]. Available:

http://www.paintballsentry.com/News.htm. [Accessed: Feb 8, 2011].

[21] BAE Systems. TRT-25MM Tactical Remote Turret [Online]. Available:

http://www.baesystems.com/ProductsServices/bae_prod_trt25mm.html. [Accessed: Feb

8, 2011].

[22] DigiKey. E32D401HPN392MDD0M [Online]. Available:

http://parts.digikey.com/1/parts/1848038-cap-3900uf-400v-screw-

e32d401hpn392mdd0m.html. [Accessed Feb 16,2011].


http://www.microsemi.com/datasheets/200GN60JDQ4_B.PDF [Accessed Feb 16,2011].

[24] Texas Instruments. DRV8821 [Online]. Available:





http://ww1.microchip.com/downloads/en/DeviceDoc/39940d.pdf



http://www.chemi-con.com/files/U32D_Web.pdf

http://www.chemi-con.com/files/U32D_Web.pdf

https://engineering.purdue.edu/ece477/Homework/CommonRefs/enviro_refs.pdf

http://en.wikipedia.org/wiki/RoHS

http://en.wikipedia.org/wiki/Polytetrafluroethylene

http://www.paintballsentry.com/News.htm

http://www.baesystems.com/ProductsServices/bae_prod_trt25mm.html

http://parts.digikey.com/1/parts/1848038-cap-3900uf-400v-screw-e32d401hpn392mdd0m.html

http://parts.digikey.com/1/parts/1848038-cap-3900uf-400v-screw-e32d401hpn392mdd0m.html





-33-

[26] Canon USA. VC-C50i [Online]. Available:

http://www.usa.canon.com/cusa/consumer/products/security_video_solutions/analog_pa

n_tilt_zoom_video_cameras/vc_c50i_vc_c50ir. [Accessed: Feb 17, 2011].

[27] The Institute for Interconnecting and Packaging Electronic Circuits. Generic Standard

on Printed Board Design [Online]. Available: http://www.the-

bao.de/divers/ipc2221.pdf. [Accessed: Feb 24, 2011].






[30] National Semiconductor. LP3872 [Online]. Available:

http://www.national.com/mpf/LP/LP3872.html#Overview. [Accessed: Feb 20, 2011].

[31] National Semiconductor. LM2677S-12 [Online]. Available:

http://www.national.com/pf/LM/LM2677.html#Overview. [Accessed: Feb 20,2011].

[32] Sanjaya Maniktala. Simple Switcher PCB Layout Guidelines [Online]. Available:

http://www.national.com/an/AN/AN-1229.pdf. [Accessed: Feb 24,2011].

[33] Microchip Technologies Inc., ―PIC24FJ64GB004 Family Data Sheet,‖ Microchip

Technologies Inc., 2010. [Online]. Available:

http://ww1.microchip.com/downloads/en/DeviceDoc/39940d.pdf [Accessed: Mar. 22,

2011].

[34] CACE Technologies. ―Winpcap manual and tutorial,‖ CACE Technologies, 2005-2009.

http://www.winpcap.org/docs/docs_412/html/main.html [Accessed: Mar 18, 2011].

[35] Sly Technologies, INC. ―Jnetpcap Documentation,‖ Sly Technologies, 2005-2011.

http://jnetpcap.com/documentation [Accessed: Mar 20, 2011].

[36] ―Barry's Coilgun Design Site,‖ http://www.coilgun.info/about/home.htm [Accessed:

April 30, 2011].



http://www.the-bao.de/divers/ipc2221.pdf

http://www.the-bao.de/divers/ipc2221.pdf



http://www.national.com/mpf/LP/LP3872.html#Overview

http://www.national.com/pf/LM/LM2677.html%23Overview

http://www.national.com/an/AN/AN-1229.pdf

http://ww1.microchip.com/downloads/en/DeviceDoc/39940d.pdf

http://www.winpcap.org/docs/docs_412/html/main.html

http://jnetpcap.com/documentation

http://www.coilgun.info/about/home.htm


A-1

Appendix A: Individual Contributions

A.1 Contributions of Stephen Wolf:

My major technical contributions to the project were the overall system design, the

majority of the schematic and circuit design, half of the PCB layout, most of the hardware

component soldering and debugging, and some of the low level microcontroller routines. In

addition to this I was the team leader and led the management role in assigning tasks to other

team members.

The beginning of the semester was spent in the planning stages. I was the team member

responsible for the constraint analysis homework and choosing essentially all of our initial

systems such as power supplies, microcontroller, motor system, IGBT, etc. I chose to design our

system around a PIC24 microcontroller using an I2C serial communication bus to communicate

with all the other devices on the board such as a specialized motor microcontroller and the

charging system for the high voltage. I also designed our high voltage charging system around

an alternating current switching triac and a rectifier, although it was Brian who carried out the

implementation of this. I also did some initial CAD work to get a general idea of the packaging

and turret design.

The next few weeks I created the schematic for the communication board containing our

microcontroller, power supplies, motor control, and I2C bus. This involved careful reading of

datasheets for pinouts and auxiliary component selection such as inductors, headers, bulk

capacitors, etc. I also created PCB decals for almost every part on the communication board to

be used in the PCB layout. I was also responsible for the PCB layout of this board as it is more

complicated than the power PCB and I had previous experience with PCB layout. I assisted

Brian with the layout of the PCB he was responsible for as well.

After spring break when the boards arrived, I was the primary team member responsible

for soldering components on the communication board, especially those parts with extremely

small pins such as the motor microcontroller. I placed and tested both our power supplies on the

board and successfully debugged them, although I did blow up a 12V supply once while testing

from wall power. After soldering the microcontroller on the board I worked with Fuhe to get

MPLAB up and running and programming our device. Fuhe and I then worked together to get

the I2C bus up and talking to the port expanders. Once the I

2C code was written, I wrote code to

talk to the motor microcontroller and get our motors spinning. A considerable amount of time

was spent getting the provided libraries from microchip for USB communication to function with

our device.

Once all the components on the communication board were soldered and functional I

started to help Brian test the components on the power PCB. Unfortunately many of the parts on

the power PCB had incorrect pin layouts and I spent a significant amount of time flywiring and

replacing components on that board. Once all of these components were working using basic

routines on the microcontroller, I then worked with Fuhe and Kirk to integrate all of this into a


A-2

program that could be controlled from the external GUI. I was able to get the high voltage

circuit to successfully charge the capacitors up to 350V as well as the coil firing circuit to

discharge these capacitors safely at 500A.

The weeks leading up to the end of the project were spent primarily on packaging. I

worked with Chuck as well as Central Machine shop to get the metal for our box cut and bent

into a usable form. Chuck helped me create a motor mount system to mount to the Lazy Susans

we had, and I then spent a large amount of time in the machine shop in the Physics building

drilling holes, milling aluminum, and performing other tasks to get the final packaging into a

usable form. Finally, I worked with the entire team to finalize all the code, test the project in its

packaged form, and demonstrate our PSSCs.

A.2 Contributions of Kirk Iler:

My major technical contributions to the project were the camera based target recognition

and the Atom processor Visual Studio program. As these topics are related to my previous

research over the summer, I was able to use the opportunity to build upon my previously learned

knowledge.

I was entirely responsible for the configuration of the Visual Studio C++ project and

Atom processor executable functionality. Around 20 hours were spent explicitly debugging

Visual Studio configurations. The camera code was initially configured in a Visual Studio

project according to my previous research. The Ethernet packet libraries were then configured to

be compatible with the same project by me, though the executable code was written by Fuhe.

The USB sample codes required further library installations. As the USB codes came with

dedicated project configurations, much debugging was necessary in order to get successful

finalized project configurations compatible with all of the camera, network, and USB codes.

Once the Visual Studio executable was compiled on a department networked computer, the

executable was moved to the Atom processor and further debugging was necessary in order to

configure the Atom processor to run the executable successfully.

I was also entirely responsible for implementing the Visual Studio C++ OpenCV library

based camera target recognition. Around 25 hours was spent implementing this functionality

including image acquisition, color blob thresholding, interpreting X, Y, and Z coordinates in

space based on known object size, measured major axis length, and known camera angular field

of view, interpreting the coordinate transformations from the camera to the motor, and

determining the amount the motor is required to turn to target the object.

I was highly involved along with Stephen and Fuhe in a lengthy attempt to configure and

debug the USB communication which ultimately did prove successful. Originally the sample

code provided by Microchip was unable to communicate with the Visual Studio project provided

by Microchip. Debugging involved analysis of the enumeration process, driver integrity,

Windows log of device manager processes, and microcontroller configuration settings. Though


A-3

unfortunately I personally spent around 10 hours debugging in the wrong direction, the time was

not wasted, as much was learned during the endeavor.

When I was not required to spend time on my own portion of the project, I was sure to be

available to assist my teammates where reasonable. The rest of my contribution can be attributed

to assisting Fuhe with software implementation and debugging, and assisting Stephen and Brian

with various tasks relating to hardware such as soldering, crimping, and helping wind coils

among other things.

Though Stephen was the primary leader for the group, I was sure to be involved with the

rest of the project and take responsibility for certain tasks where applicable. I was also sure to

frequently discuss the implementation timeline with Stephen and provide caution about how his

decisions related to time constraints. As Stephen was out of town for proof of parts and printed

circuit board submission, I was required to take responsibility for ensuring printed circuit board

changes were implemented by the team as recommended by the teaching assistants by the

submission deadline. At the end of the semester, I assumed responsibility for ensuring the

team’s completion the final documentation.

A.3 Contributions of Fuhe Xu:

My assigned role for this project was the software developer, and I was in charge of

writing, refining, and debugging most of the software we used in our devices, with notable

exceptions being the image processing software, the C+ configurations, and the USB framework.

Of all the group members I had the most experience with software, as I was the only Computer

Engineering student and I have had plenty of experience with software development due to my

work experience. I developed the GUI, the functions and software flow on the microcontroller,

and the packet sending conventions on both the Ethernet line and the USB line. I helped develop

the software flow for all of our software-using devices and how these flows interface with each

other.

The GUI was entirely written by me using Java swing libraries, including the

functionality to receive and update images on one panel. I also set up packet sending and

receiving functionality for both our Java and C++ software using pre-existing packet libraries

found on the internet—jnetpcap and winpcap respectively. I implemented these packet handlers

to be able to perform other program tasks upon receiving a particular packet, using an encoding I

devised and recorded in both the Java and C++ programs. I then wrote the packet handler

functions to work in such a way that other commands could be called through packet handlers,

and tested bi-directional packet sending between the Java and C++ programs through each

console.

I helped figure out the USB device configurations, although the crux of that effort was

Stephen and Kirk, and after we found a framework file that worked, I distilled it into easily

accessible functions that could be used in our code, specifically ones that could interface with


A-4

Ethernet packet functions and camera functions. In addition, I devised the encoding for these

packets and set up the communication between the C++ code and microcontroller code.

As for the microcontroller code, I handled the actual code itself while Stephen essentially

told me how to do the hardware interfacing portions—clock frequencies, port pins, and device

configurations—for each peripheral the microcontroller would talk to. I devised functions and

abstractions for code interfaces to facilitate the final program flow development. I laid the

groundwork for converting Ethernet packets into USB commands, allowing a simple two-byte

packet over the USB line to be translated into motor movement and capacitor charging,

discharging, firing, and disabling.

Along with Kirk I figured out a way to receive encoded images over Ethernet and decode

them into visuals on the GUI using only the pcap library and native C++ and Java file handling

methods and Java swing components. I also worked with Kirk to develop the algorithm that

would synchronize the camera’s target reading to motor targets.

As my specialization was strongly in software over multiple platforms, I was woefully

incapable of contributing much to hardware design, but the software tasks involved with the

project were numerous enough that I did not have much time to work with hardware tasks

anyway. I was present to debug all the major integration tests, such as the firing and motors tests,

in case a software issue would spring up. Essentially, almost all of my contributions were on the

software side of the project.

A.4 Contributions of Brian Bentz:

Throughout the semester, I contributed to several different parts in the design and

production process of Defender. My expertises lie primarily in the areas of circuits and

electromagnetics, so the majority of my contributions to this project came in the form of

hardware and circuitry design. I worked extensively to design the packaging for Defender,

which included building the coilgun, the power PCB, and much of the general packaging. The

individual paper assignments that I wrote were the Packaging Specifications and Design

assignment and the Ethical and Environmental Impact Analysis report. These two papers helped

me to develop my ideas about the packaging of Defender.

At the beginning of the semester, I was put in charge of designing and building the

coilgun. I was given this responsibility because of my background in electromagnetics and my

general experience with high voltage and pulsed circuitry gained from internships. I started off

by doing general research about coilguns on the internet. I quickly found many different sites

where people had built their own homemade coilguns as well as several papers detailing more

precise design processes. After discussing the coilgun with my team, we decided to build a

simple single phase coil gun. We decided this because it was the simplest design and would

allow us to satisfy our PSSCs. To design the coil gun, I primarily used the resources available at

Barry’s Coilgun Design Site[36]

, as well as several other design sites. The circuit is basically a

switched RLC circuit. Our capacitance was set, and once we knew the voltage capability of our


A-5

high voltage power supply, I was able to calculate the length and size of coils we would need to

fire the projectile. The type of wire we used was 18 gauge magnet wire and we used an IGBT to

switch the RLC circuit.

Before Spring Break, I was also responsible for building one of our two PCBs, the power

PCB. This was the PCB that contained all of our high voltage circuits. These included the high

voltage power supply circuit, the low voltage power supply circuits, the capacitor bleed circuit,

and the analog to digital converters we used to measure current and voltage in the coil. The high

voltage power supply circuit uses a triac converter connected to an optoisolator to control the

high voltage. The low voltage transformer is located on the Power PCB, and connects to a

rectifier to supply the 12V for the motors on the other PCB. When the power PCB finally came

in, I worked primarily with Stephen to debug the board. We quickly discovered that I had

incorrectly laid out many of the components for which I had used a header file that already

existed in PADs. This required a lot of fly wiring to fix, but we ended up getting both boards up

and working.

After spring break I was primarily responsible for the packaging of Defender. I spent a

lot of time figuring out how all of our components would fit together. We decided at the start of

the semester that we wanted a metal box to minimize EMI. However the only metal boxes sold

online were either too small or way too expensive. We ended up buying sheets of aluminum,

and cutting them to build our own metal box. I worked especially towards the end of the

semester drilling holes and cutting aluminum in order to mount all of our components in the box.

I also worked to build the arm part of the turret, which included the barrel and Lazy Susans. I

mounted the barrel and coil in the turret, and wired up and connected all five of our position

sensors across the barrel. The most difficult part of the packaging was making sure that all of the

components lined up correctly. Our packaging is very large and required a large amount of

customization.

If I had more time I would fix the power PCB so that none of the fly wiring would be

necessary. I would also add several packaging components, including places for speakers and a

keypad. To speed up the projectile, I would like to remake the coilgun as a multi stage coil gun.

In the process I would increase the diameter of the barrel so that it could be slotted. This would

reduce eddy currents and drastically increase the efficiency of our coilgun.


B-1

Appendix B: Packaging

Power PCB

Communications PCB

Atom Board

Capacitor Bank

Figure B.1: Interior Packaging Design

Figure B.2: Exterior Packaging-Turret


B-2

Figure B.3: The final packaging


C-1

Appendix C: Schematic

Subsystem A: Power Systems

Figure C.A.1 12 Volt Supply

Figure C.A.2 Rectifier Figure C.A.3 Wall Fuse


C-2

Figure C.A.4 High Voltage supply + Capacitor Bleed + I2C

Figure C.A.5 12 V connectors

Figure C.A.6 Connectors between Power

and Communications boards


C-3

Figure C.A.7 Rectified Connectors

Figure C.A.8 Low Voltage Headers

Figure C.A.9 High Voltage Headers


C-4

Subsystem B: Microcontroller

Figure C.B.1 Microcontroller and Connections

Figure C.B.2 Keypad Encoders


C-5

Figure C.B.5 USB Connectors

Figure C.B.3 Photosensor Connectors:

Clockwise from Top Left: Photosensor inputs, photosensor

ground, photosensor power, photosensor LEDs

Figure C.B.4 In-Circuit Debugger Connector


C-6

Subsystem C: Motors

Figure C.C.1 Motor controller and I2C Port Expander

Figure C.C.2 Motor Connectors


D-1

Appendix D: PCB Layout Top and Bottom Copper

Figure D.1 Communication PCB Top

Figure D.2 Communication PCB Bottom


D-2

Figure D.3 Power PCB Top

Figure D.4 Power PCB Bottom


E-1

Appendix E: Parts List Spreadsheet

Communications PCB

Man. Part Number Part Description Price per Unit Quantity Price

LLA215R70J474MA14L Bypass for V3P3 6.3V, .47uF 0.386 10 3.86

500R15N330JV4T 33pF capacitor, clock, ceramic 0.044 10 0.44

CC0805KRX7R9BB103 50V, .01uF for VCP1/VCP2 0.048 10 0.48

C4532X7R1H475M 4.7uF 0.804 2 1.61

F951A106MPAAQ2 output filter cap 10uF tantalum 1.14 2 2.28

C0805C104K5RACTU 50V, .1uF, VM 0.105 10 1.05

GRM219R71C104KA01D 16V, .1uF bypass 0.081 20 1.62

GRM21BF50J106ZE01L Micro and Motor: Regulator 10uF, 6.3V 1.64 10 16.4

B360A-13-F Schottky diode 0.55 2 1.10

PM2110-680K-RC 68 uH 2.73 2 5.46

ERJ-6ENF3300V 330, 0805 0.07 2 0.14

ERJ-6ENF1001V 1k, 0805 0.07 2 0.14

ERJ-6ENF1003V 100k, 0805 0.07 5 0.35

ERJ-6ENF7500V 750, 0805 0.07 6 0.42

CRCW08051R27FKEA 1.25 ohm sense resistor 0.089 10 0.89

ERJ-6ENF3002V 30k, 0805 0.07 6 0.42

ERJ-6ENF3901V 3.9k, 0805 0.07 2 0.14

ERJ-6ENF1002V 10k, 0805 0.07 18 1.26

PIC24FJ64GB004 Micro 5.38 0 0

320.01E11RED Reset Switch 1.99 2 3.98

DRV8821DCA Motor Controller 6.72 0 0

MCP1525T-I/TT Voltage Reference 0.92 2 1.84

MCP23016-I/SS I2C Port Expander 2.03 2 4.06

SX1508IULTRT Keypad Encoder 1.56 3 4.68

LP3872EMP-3.3/NOPB 3.3v Rail 3.72 2 7.44

EMZA100ADA102MJA0G Input Filter Cap, 1000uF, electrolytic 1.094 5 5.47

LM2677S-12/NOPB 12V rail 7.80 2 15.60

APXE160ARA680MF61G output cap, 68uF 1.60 5 8.00

640456-2 2 pin 0.32

0


E-2

640456-3 3 pin 0.34 3 1.02

640456-4 4 pin 0.33 2 0.66

640456-5 5 pin 0.38 4 1.52

640456-6 6 pin 0.37 2 0.74

640456-9 9 pin 0.5 3 1.50

216548-1 RJ-11 for ICD 1.49 2 2.98

690-004-621-023 USB-B Connector 1.36 2 2.72

subtotal 100.268

Power PCB


PL56-24-130B

12V supply Transformer; 12V @4.66A, [email protected] (Through Hole) 26.73 1 26.73

MAX1363EUB+

Analog to Digital Inverter; I2C data interface, 133k sampling rate; Surface Mount 13.07 3 39.21

MB1S-TP Low Voltage Rectifier (3.3V); 70V RMS, 0.5A (surface Mount) 0.44 2 0.88

GBU4J Low Voltage Rectifier (12);600V RMS, 4A (surface Mount) 1.91 2 3.82

LMB8S-TP High Voltage Rectifier; 560V RMS, 1A (surface mount) 0.58 2 1.16

P6SMB400A

High Voltage Protection Diode; 380-420V breakdown (surface mount) 0.75 5 3.75

PWR263S-20-1002F 20W, 10kohm Resistor; 1% tolerance 4.68 2 9.36

ERJ-8ENF1204V 1.2Mohm, 0.25W, Thick Film, 1% tolerance 0.10 5 0.50


E-3

PNM0805E5001BST5 5kohm, 2W, 0.1% tolerance, thin film 1.40 5 7.00

MCP23008-E/SS 1.8V-5.5V I2C bus; 1.7 MHz clock; Surface Mount 1.32 2 2.64

ERJ-M1WSF3M0U 0.003 ohm; 1W Resistor (Surface Mount) 1.00 2 2.00

08055C104JAT2A 0.1uF 50V Capacitor; Ceramic Surface Mount 0.05 10 0.50

C4532X7R1H475M

4.7uF 16V Capacitor 0.80 3 2.41

RMCF0805JT2K00 2k ohm, 1/8W, 5% tolerance Resistor 0.03 10 0.30

STGB20NC60V 600V Vce, 20A cont, 200W IGBT (Surface Mount) 3.13 2 6.26

Q6008DH3RP

600V off state voltage; 8A on state current; 1.3V trigger; (Surface Mount) 1.98 2 3.96

MOC3052SR2VM

Voltage off state: 600V; 60mA DC forward current (Surface Mount) 1.02 2 2.04

BSS138K

50V VDS breakdown; 1.2V Vgs max @ 250uA, 360mW; (Surface Mount) 0.43 5 2.15

ERJ-6GEYJ620V 62 ohm; 1/8 W; Thick Film; 5% tolerance; (Surface Mount) 0.04 10 0.40

ERJ-6GEYJ511V 510 ohm; 1/8W resistor; 5% tolerance; 0.04 10 0.40

TDH35P300RJE 300 ohm power resistor; 35W, Thick Film 7.70 4 30.80


E-4

39605000440 Slow Blow; 500mA; 125VAC; Through Hole 0.99 2 1.98

H11L2SR2M

7500V hold off; 50mA; 1Mz; 10mA forward current; (Surface Mount) 1.42 4 5.68

ERJ-6GEYJ101V 100 ohm 1/8W current limiting resistor 0.04 10 0.40

640456-4 4 pin 0.33 2 0.66

640456-6 6 pin 0.37 2 0.74

640456-2 2 pin 0.32 3 0.96

1-770170-0 3-Pin Power header 0.98 4 3.92

1-770166-0 2-Pin Power header 0.91 4 3.64

164.252

Off-board


263CX Transformer one filament 77.52 1 77.52

1375820-2 2 pin signal 0.07 3 0.21

1375820-3 3 pin signal 0.11 3 0.33

1375820-4 4 pin signal 0.16 4 0.64

1375820-5 5 pin signal 0.20 4 0.80

1375820-6 6 pin signal 0.23 4 0.92

1375820-9 9 pin signal 0.35 3 1.05

794184-1 2 pin power 0.73 4 2.92

794187-1 3 pin power 0.77 4 3.08

1375819-1 Signal 0.024 150 3.60

794221-1 Power 0.0604 25 1.51

OPB917BZ Optical Sensor 4.97 3 14.91

APT200GN60JDQ4 Coilgun firing IGBT 42.60 2 85.2

42BYG023-R Stepper Motor 20.95 2 41.90

RadioShack parts 8.50 1 8.50

subtotal 243.09

Digi-key Order 2


39605000440 Slow Blow; 500mA; 125VAC; Through Hole 0.99 3 2.97

ERJ-6ENF5490V 549 resistor for photosensor led 0.07 7 0.49

701W-15/31 Wall power entry 1.00 1 1.00


E-5

1.00 0.89 0.89

640456-5 5 pin 0.38 2 0.76

1375820-5 5 pin signal 0.2 4 0.80

3 pin power 0.69 3 2.07

Keypad 14.34 1 14.34

Possible 50V filter cap 2.23 2 4.46

Possible 50V filter cap 1.08 2 2.16

high freq filter cap 3.00 0.05 0.15

Power resistor for triac 1.00 3.3 3.30

load resistor for 12V 2.00 0.71 1.42

LM2677S-12/NOPB 12V rail 7.8 2 15.60

subtotal 50.41

Digi-key Order 3

Distributor Part Number Part Description Price per Unit Quantity Price

APT2X101DQ100J-ND DIODE DUAL PAR 100A 1000V SOT227 27.53 2 55.06

TLP701FCT-ND IC IRED PHOTOCOUPLER 6SMD 1.25 3 3.75

541-1.50CCCT-ND RES 1.50 OHM 1/8W 1% 0805 SMD 0.089 10 0.89

TGHGCR0020FE-ND RES .002OHM 1% 100W CURRENT SNSE 27.21 1 27.21

365-1264-ND SENSOR SWITCH LOGIC SLOTTED OPT 4.97 2 9.94

A100826CT-ND CONN SCKT MNI-UMNL2 22-18AWG TIN 0.0604 30 1.81

A100825CT-ND CONN PIN MINI-UMNL2 22-18AWG TIN 0.07 10 0.70

53892-4-ND CONN TERM 12-18AWG CRIMP PWR LOK 0.42 10 4.20

53894-2-ND CONN HOUSING POWER LOCK 1POS BLK 0.69 2 1.38

53894-4-ND CONN HOUSING POWER LOCK 1POS RED 0.69 2 1.38

53894-3-ND CONN HOUSING POWER LOCK 1POS GRN 1.23 2 2.46

subtotal 108.782


E-6

Digi-Key Order 4

Distributor Part Number Part Description Price per Unit Quantity Price

LMB8S-TPMSCT-ND BRIDGE RECTIFIER 1A 800V LMBS-1 0.58 3 1.74

MOC3052SR2VMCT-ND OPTOCOUPLER TRIAC VDE 6-SMD 1.02 3 3.06

Q6008DH3RPCT-ND ALTERNISTOR 600V 8A D-PAK 1.98 3 5.94

568-3696-1-ND TRIAC 600V 4A DPAK 0.93 2 1.86

568-3660-1-ND TRIAC 600V 8A DPAK 1.02 2 2.04

TLP701FCT-ND IC IRED PHOTOCOUPLER 6SMD 1.25 2 2.50

PPC100W-3JCT-ND RES 100 OHM METAL FILM 3W 5% 0.71 2 1.42

493-1116-ND CAP 4700UF 50V ELECT VR RADIAL 2.83 2 5.66

P0.0ACT-ND RES 0.0 OHM 1/8W 0805 SMD 0.04 3 0.12

A100826CT-ND CONN SCKT MNI-UMNL2 22-18AWG TIN 0.07 10 0.70

A100825CT-ND CONN PIN MINI-UMNL2 22-18AWG TIN 0.07 10 0.70

A100434CT-ND CONN PIN 16-20AWG MINI-U M-N-L2 0.32 10 3.20

A100435CT-ND CONN SCKT 16-20AWG MINI-U M-N-L2 0.33 10 3.30

A25657-ND CONN CAP 3POS MINI UNIV-MATE 2 0.77 5 3.85

A25656-ND CONN PLUG 3POS MINI UNIV-MATE 2 0.69 5 3.45

subtotal 39.54

Miscellaneous and Total

Sources Price

Aluminum 100.00

Mcmaster 21.80

Magnet wire 32.66

Hardware 110.79

subtotal 265.25

Total: 971.59


F-1

Appendix F: FMECA Worksheet

High Voltage and Capacitor Subsystem

Failure

No.

Failure Mode Possible Causes Failure Effects Method of

Detection

Criticality Remarks

A1 Output of 3.3V

supply = 0V

Low input from

transformer, regulator

failure

Microcontroller

and its peripherals

will not operate

Observation Low Inconvenience to user

A2 Output of 12V

supply = 0V

Low input from

transformer

Capacitor

discharge, coil

system, motors

will not operate


A3 Output of HV =

0V

Low input from

transformer

Capacitors will

not charge


A4 Output of 3.3V

supply > 3.3V

Regulator failure,

Excess from

transformer

Microcontroller

and its peripherals

may be damaged

Observation Medium Mitigated with fuses,

some parts undergo

thermal shutdown

A5 Output of 12 V

supply > 12 V

Regulator failure,

Excess from

transformer

Capacitor

discharge, coil

system, motors

may be damaged

Observation Medium Mitigated with fuses,

some parts undergo

thermal shutdown


F-2

A6 Output of HV

supply > 400V

Regulator failure,

Excess from

transformer

Injury to user and

anyone around

Observation High Mitigated with fuses

A7 Capacitors

shorted

Breakdown of

Capacitor Dielectric

Explosion, Injury Observation High Capacitors are tested

externally before

operation, diodes placed

Microcontroller and Atom subsystem

Failure

No.


Detection

Criticality Remarks

B1 Input to VDD, VSS,

AVDD, AVSS out

of tolerance

Power rail failed,

bypass capacitor

shorted

PIC24F fails to

operate, may

suffer damage

Observation Medium

B2 PIC24 does not

output to I2C

expander tied to

motors

Stuck in a polling

loop for USB

commands, Interrupts

preventing

transmission, Wrong

slave address sent

Motors will not

move

Observation Low Cannot aim coilgun

B3 PIC24 does not

output to I2C

expander tied to

capacitor circuit

Stuck in a polling

loop for USB

commands, Interrupts

preventing

transmission, Wrong

slave address sent

Coilgun discharge

mistimed,

projectile may be

fired backwards

Observation High A backwards projectile

can harm an unwary

user or cause

unintended property

damage


F-3

B4 PIC24 and Atom

board do not

communicate

over USB line

USB configurations

wrong on either end,

Microcontroller

cannot trigger

other peripherals

Observed

indirectly—

through atom

board and other

functions

Low No functioning

B5 PIC24 does not

output I2C signal

to keypad

Stuck in another loop,

i.e. timing or USB

polling loop, slave

address sent

incorrectly

Keypad activation

will not work

Observation Low User unable to identify

self, no action taken by

device

B6 Keypad encoder

does not receive

input from

keypad

Connection between

encoder and keypad

shorted

Keypad activation

will not work

Observation Low User unable to identify

self, no action taken by

device

B7 Ethernet packets

to atom board

misread

Packet filtering not

implemented

vigorously enough

(Manual

operation mode) –

Commands not

sent to atom

board will be

processed

Observation High Will only happen in

manual operation mode

B8 Ethernet packets

from atom board

misread

Packet filtering not

implemented

vigorously enough

(Automatic

operation mode) –

GUI will fail to

reflect what is

actually

happening

Observation Low


F-4

Motors Subsystem

Failure

No.


Detection

Criticality Remarks

C1 Motor controllers

overheat

Excess Current going

into motor controllers

Motor controllers

shut down,

motors will not

function without

controllers

Observation Medium Motor controllers may

need to be replaced

C2 Motors hit an

(internal) hard

stop

Control timing

missed

Motor position

lost, control

possibly lost,

damage to

packaging

Observation Medium

Documents

EE 477 Final Report - Purdue Engineering 477 Final Report Fall 2010 Team 6 Defender ... 1.0 Project Overview and Block Diagram ... The camera for target tracking is a Canon VC-C50i[1]