Designing An Electronic Trigger Mechanism For A Paintball Marker To

Allow User Selectable Firing Rates

ECE 4884/4007

Fall 2007

Nathan Densmore

Matthew Roese

Andrew Adams

Chris Britton (Team Leader)

Georgia Institute of Technology ECE 4007 Fall 2007

Overview

• Design and implement an electronic trigger

• Upgrading is more practical compared to other high end electronic markers

• Target customers will be scenario paintball enthusiasts

• Principal expense is development cost

Georgia Institute of Technology ECE 4007 Fall 2007

Design Objectives

• Electronic trigger upgrade for the 98 Custom paintball marker

• Two firing modes: semi-automatic and fully automatic

• LCD screen will display the mode and selected rate of fire

• LED indicator for low ammunition and selected firing mode

• User friendly up/down buttons to select the rate of fire

Georgia Institute of Technology ECE 4007 Fall 2007

Design Approach

• Key component is PIC Microcontroller (16F690)

• Powered by 9V battery

• Trigger pressed will activate the micro switch allowing 9V signal to energize the solenoid

• PIC will output to an LED indicating firing mode

• PIC will output to LCD module indicating firing mode and rate

Georgia Institute of Technology ECE 4007 Fall 2007

Top Level Design of Circuit Components

PICMicrocontroller

Supply

Push Button

Push Button

Trigger

LED

LCDModule

Solenoid

I/O

I/O

I/O

I/O

2

8 or 4

3

Data Path

Control Inputs

I/O

I/O

I/O

I/O

3

VSS

VDD +5V

VDD +5VVSS 2

2

2

VDD +9VVSS

VSSVDD +5V

2

VDD +5VVSS

Georgia Institute of Technology ECE 4007 Fall 2007

PIC Controller

• 20 pins – 1 VDD, 1 VSS, up to 18 I/O pins

• Operates on 2.0-5.5V

• Up to 20MHz oscillator/clock

• Up to 200ns instruction cycle

• 8-bit and 16-bit timer/counters

• FLASH/EEPROM – up to 100,000 writes

Georgia Institute of Technology ECE 4007 Fall 2007

1

11

12

13

14

15

16

17

18

19

20

10

9

8

7

6

5

4

3

2

PIC

16F6

90

VDD - Supply

RB6 – Pushbutton Up Input

RB5 – LED Red Output

RB4 – LED Green Output

RC2 – LCD Data Bit 2 Output

RC1 – LCD Data Bit 1 Output

RC0 – LCD Data Bit 0 Output

RA2 – LCD Register Select Output

RA1 – Trigger Input

RA0 – Supply (Firing Mode) Input

VSS - Supply

RB7 – Pushbutton Down Input

RC7 – LCD Data Bit 7 Output

RC6 – LCD Data Bit 6 Output

RC3 – LCD Data Bit 3 Output

RC4 – LCD Data Bit 4 Output

RC5 – LCD Data Bit 5 Output

RA3 – LCD Read/Write Output

RA4/CLKOUT – Solenoid Output

RA5 – LCD Enable Output

PIC Microcontroller

Georgia Institute of Technology ECE 4007 Fall 2007

PIC Programming Environment

• MPLAB Integrated Development Environment (IDE) included as tool to program PIC

• MPLAB is programmed in assembly language

• PIC Kit 2 software responsible for debugging code and loading chip

Georgia Institute of Technology ECE 4007 Fall 2007

Pseudo-code ExampleSet BPS default; Set Ball Count;

When ROF switch Semi or FullLED

if Semi ROF GREEN Solidif Semi ROF RED Solid

LCDif Semi ROF Display “Semi”if Full ROF Diplay “Full” and BPS

PUSHBTNif Full ROF

when UP PUSHBTN BPS + = 1when DOWN PUSHBTN BPS - = 1when UP & DOWN BPS = 0, Go to LED, LCD

Georgia Institute of Technology ECE 4007 Fall 2007

Power Supply Schematic

Georgia Institute of Technology ECE 4007 Fall 2007

Debounced Trigger Circuit

• “Beginning” of circuit, and activated when trigger is pulled

• Switch will send a high input to the PIC controller

Georgia Institute of Technology ECE 4007 Fall 2007

Push Buttons (Up/Down)

• UP and DOWN pushbuttons are inputs to the PIC; used only when in Full Auto Mode

• UP pushbutton will increase firing rate; DOWN will decrease firing rate

• Both UP and DOWN selected simultaneously will RESET ball count

Georgia Institute of Technology ECE 4007 Fall 2007

LED Mode Indicator

• Semi Mode:

Green LED• Full Mode:

Red LED• Low Ammo Status:

LED alternates red and green

Georgia Institute of Technology ECE 4007 Fall 2007

LCD Module

• Display numbers and words

• More versatile than 7- segment LED

• Line length 8 characters

• 14 pins in order to interface PIC controller

• 8 data lines, 3 control lines, & 2 power lines

• Time delay between LCD and PIC interface

PIC LCD Module

4

7

8

9

14

13

10

11

12

5

6

1- Ground2 - VDD

17

16

15

14

9

8

7

6

5

4

2

Data bit 7

Register Select

Data bit 0

Data bit 1

Enable

Read/Write

Data bit 5

Data bit 4

Data bit 3

Data bit 2

Data bit 6

Georgia Institute of Technology ECE 4007 Fall 2007

Solenoid

• Powered by +9V

• PIC outputs +5V and closes transistor circuit

• Current freely flows and fires the solenoid

• PIC outputs 0V and opens transistor circuit

• Current stops flowing and solenoid returns to initial state

• Diode prevents residual current from damaging transistor

Georgia Institute of Technology ECE 4007 Fall 2007

Mechanical Operation

• Operator pulls trigger• Trigger throws trigger switch• Solenoid fires and forces rod

upward• Rod rotates sear rocker pin and

releases bolt• Bolt spring sends bolt forward

inducing firing operation• Blowback resets bolt, locking

sear into initial position• Solenoid magnet resets

solenoid to initial position

Georgia Institute of Technology ECE 4007 Fall 2007

Component Enclosure

• Plastic enclosure will

mount on marker’s magazine

• Enclosure will house all of the electronic trigger assembly

Georgia Institute of Technology ECE 4007 Fall 2007

Technical Advantages and Disadvantages

• LCD module is more flexible than 7-segment LED display

• Relatively inexpensive production cost

• Circuit components are easily replaceable98

• Circuit design larger than existing products

• LCD module is bulky

Georgia Institute of Technology ECE 4007 Fall 2007

Marketing Advantages

• Ability to change firing modes quickly• Able to change rate of fire efficiently• Easy operator interface allows for quick selection of

system configurations• LCD data display• No special tool or manual to switch modes or firing rates

Georgia Institute of Technology ECE 4007 Fall 2007

Cost AnalysisDesign Cost

Purchased Item Description Quanity Unit Price Amount

Digi-Key Corporation Resistor 4.7K Ω 6 0.15 0.90

Digi-Key Corporation Resistor 1K Ω 1 0.15 0.15

Digi-Key Corporation Resistor 150 Ω 2 0.15 0.30

Digi-Key Corporation NPN Transistor 1 0.11 0.11

Digi-Key Corporation 2-In Nand Gate 2 0.56 1.12

Digi-Key Corporation Rectifier GPP 50V 1 0.26 0.26

Digi-Key Corporation Lever Switch 1 1.10 1.10

Digi-Key Corporation Pushbutton Switch 2 3.04 6.08

Digi-Key Corporation Rocker Switch 1 1.80 1.80

Digi-Key Corporation Regulator 1 0.72 0.72

Digi-Key Corporation Capacitor .1µF 1 0.11 0.11

Digi-Key Corporation Capacitor .33µF 1 0.15 0.15

Digi-Key Corporation 9V Battery Lead 1 0.33 0.33

Digi-Key Corporation LED Light 1 0.75 0.75

Digi-Key Corporation 8x1 LCD Module 1 24.24 24.24

Digi-Key Corporation PIC16F57 28-DIP 1 1.55 1.55

Digi-Key Corporation PIC16F628A 18-DIP 1 3.35 3.35

Digi-Key Corporation PICKIT 2 Starter Kit 1 49.99 49.99

Adv. Paintball Electronics Solenoid 1 19.95 19.95

Tippmann Parts Bag of Parts for Trigger 1 16 16.00

Shipping Cost 16.96

Total Design Cost 145.92

Georgia Institute of Technology ECE 4007 Fall 2007

Future Work

• Program the PIC microcontroller to fire paintball marker (2 weeks)

• Design an etched circuit board for more efficient production (1 week)

• Program PIC microcontroller to work with LCD module (4 days)

• Assemble product and test on marker

(3 days)