Dtmf Based Wireless Mobile Robot

DTMF BASED WIRELESS MOBILE ROBOT

CHAPTER 1

1.1 INTRODUCTION:

Conventionally, Wireless-controlled robots use DTMF circuits, which have the

drawbacks of limited working range, limited frequency range and the limited control.

Use of a mobile phone for robotic control can overcome these limitations. It provides

the advantage of robust control, working range as large as the coverage area of the

service provider, no interference with other controllers. Although the appearance and

the capabilities of robots vary vastly, all robots share the feature of a mechanical,

movable structure under some form of control.

The Control of robot involves three distinct phases: perception, processing and action.

Generally, the preceptors are sensors mounted on the robot processing is done by the

on- board microcontroller or processor, and the task is performed using motors or with

some other actuators.

In privies day it is very difficult to move the wired robot in different places for the

work due to wired they caused many problems at the time of operation .so to

overcome this problem we use wireless mobile operated robot.

Adding different application with robot we will use it like fire fighting, lpg & smoke

alarm web cam etc which is very helpful for us to reduced the time and increasing in

processing time.

AIM

To construct a DC motor based Robot that can be controlled from any distance just by

pressing some buttons on a cell phone.1 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOWDTMF BASED WIRELESS MOBILE ROBOT

1.2Project Overview:

In this project, the robot is controlled by a mobile phone that makes a call to the

mobile phone attached to the robot. In the course of a call, if any button is pressed, a

tone corresponding to the button pressed is heard at the other end of the call. This tone

is called ‘dual-tonemultiple-frequency’ (DTMF) tone. The robot perceives this DTMF

tone with the help of the phone stacked in the robot. The received tone is processed by

the ATmega16 microcontroller with the help of DTMF decoder MT8870. The decoder

decodes the DTMF tone into its equivalent binary digit and this binary number is sent

to the microcontroller. The microcontroller is preprogrammed to take a decision for

any given input and outputs its decision to motor drivers in order to drive the motors

for forward or backward motion or a turn. The mobile that makes a call to the mobile

phone stacked in the robot acts as a remote. So this simple robotic project does not

require the construction of receiver and transmitter units. DTMF signaling is used for

telephone signaling over the line in the voice-frequency band to the call switching

centre. The version of DTMF used for telephone tone dialing is known as ‘Touch-

Tone DTMF assigns a specific frequency (consisting of two separate tones) to each

key so that it can easily be identified by the electronic circuit. The signal generated by

the DTMF encoder is a direct algebraic summation, in real time, of the amplitudes of

two sine (cosine)waves of different frequencies, i.e., pressing ‘5’ will send a tone

made by adding 1336 Hz and

770 Hz to the other end of the line. The tones and assignments in a DTMF system are

shown in Table I & there is a wireless camera is attached to this electronic car. This

camera is used to see the vision of external environment. This camera work to see the

outside. When this complete car is moving in a room it show the picture of this room.2 DEPARTMENT OF ELECTRONICS MITS,

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Block Diagram:

Fig No 1.1 connection3 DEPARTMENT OF ELECTRONICS MITS,


1.3 Schematic of cell phone operated robot:

Fig shows the block diagram of the microcontroller-based mobile phoneoperated land

rover. The important components of this rover are a DTMF decoder, microcontroller

and motor driver. An MT8870 series DTMF decoder is used here. All types of the

MT8870 series use digital counting techniques to detect and decode all the 16 DTMF

tone pairs into a 4-bit code output. The built-in dial tone rejection circuit eliminates

the need for pre-filtering.

When the input signal given at pin 2 (IN-) in single-ended input configuration is

recognized to be effective, the correct 4-bit decode signal of the DTMF tone is

transferred to Q1 (pin 11) through Q4 (pin 14) outputs. Table II shows the DTMF data

output table of MT8870. Q1 through Q4 outputs of the DTMF decoder (IC1) are

connected to port pins PA0 through PA3 of ATmega16 microcontroller (IC2) after

inversion by N1 through N4, respectively. The ATmega16 is a low-power, 8-

bit, CMOS microcontroller based on the AVR enhanced RISC architecture. It

provides the following features: 16 kB of in-system programmable Flash program

memory with read-while-write capabilities, 512 bytes of EEPROM, 1kB SRAM,

32general-purpose input/output (I/O) lines and 32 general-purpose working registers.

All the 32 registers re directly connected to the arithmetic logic unit, allowing two

independent registers to be accessed in one single instruction executed in one clock

cycle.

The resulting architecture is more code-efficient. Outputs from port pins PD0 through

PD3 and PD7 of the microcontroller are fed to inputs IN1 through IN4 and enable

pins (EN1 and EN2) of motor driver L293D, respectively, to drive two geared DC

motors. Switch S1 is used for manual reset. The microcontroller output is not

sufficient to drive the DC motors, so current drivers are required for motor rotation.

The L293D is a quad, high-current, half-H driver designed to provide bidirectional

drive currents of up to 600 mA at voltages from 4.5V to 36V. It makes it easier to

drive the DC motors. The L293D consists of four drivers. Pin IN1 through IN4 and

OUT1 through OUT4 are input and output pins, respectively, of driver 1 through

driver 4. Drivers 1 and 2, and drivers 3 and 4 are enabled by enable pin 1 (EN1) and

pin 9 (EN2), respectively.4 DEPARTMENT OF ELECTRONICS MITS,

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1.4 CIRCUIT DIAGRAM:

Fig No 1.2 circuit5 DEPARTMENT OF ELECTRONICS MITS,

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1.5WORKING :

In order to control the robot, you need to make a call to the cell phone attached to the

robot (through head phone) from any phone, which sends DTMF tunes on pressing the

numeric buttons. The cell phone in the robot is kept in ‘auto answer’ mode. (If the

mobile does not have the auto answering facility, receive the call by ‘OK’ key on the

rover- connected mobile and then made it in hands-free mode.) So after a ring, the

cellphone accepts the call. Now you may press any button on your mobile to perform

actions . The DTMF tones thus produced are received by the cell phone in the robot.

These tones are fed to the circuit by the headset of the cell phone.

Fig No 1.3 Working

The MT8870 decodes the received tone and sends the equivalent binary number to the

microcontroller. According to the program in the microcontroller, the robot starts

moving.6 DEPARTMENT OF ELECTRONICS MITS,


When you press key ‘2’ (binary equivalent 00000010) on your mobile phone, the

microcontroller outputs ‘10001001’ binary equivalent. Port pins PD0, PD3 and PD7

are high. The high output at PD7 of the microcontroller drives the motor driver

(L293D). Port pins PD0 and PD3 drive motors M1 and M2 in forward direction.

Similarly, motors M1 and M2 move for left turn, right turn, backward motion and stop

condition.

The input is the keypad of the telephone or the mobile. The press of any button

generates a unique combination of frequency which is fed into the decoder circuit

through the 3.5 mm headphone jack. The resistances of 100k ohm and 104 capacitor

forms a tone filter to minimize the noise introduced in the frequency spectrum. The IC

8870 has the inbuilt algorithm to convert this frequency into corresponding binary

sequence which is fed to the controller Port1 as input. The crystal oscillator of

3.597MHz is used to provide the gate pulse/trigger to the IC. The 33pf ceramic

capacitor tunes the gate pulses. On the basis of the input sequences the control is

preprogrammed to generate 4-bit output on the port 0 of the controller. This output act

as an input to the motor driver which in turn drives the DC motors to perform all the

motions.

Note: The operation can be done from remote location by making the call on the

attached phone from the location. Since the circuit acts on the DTMF the calling

phone as well as the attached phone should properly generate DTMF tones. The dc

voltage is input to the regulator which convert it into regulated +5V which input to the

whole circuit.7 DEPARTMENT OF ELECTRONICS MITS,

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1.6 Construction:

When constructing any robot, one major mechanical constraint is the number there a

two- wheel drive or a four-wheel drive. Though four-wheel drive is more complex

than two- wheel drive, it provides more torque and good control. Two-wheel drive, on

the other hand, is very easy to construct. Top view of a two-wheel-driven land robot is

shown in Fig. 1.4.The chassis used in this model is a 10×18cm 2 sheet made up of

parameter. Motors are fixed to the bottom of this sheet and the circuit is affixed firmly

on top of the sheet. A cellphone is also mounted on the sheet as shown in the picture.

In the four-wheel drive system, the two motors on a side are controlled in parallel. So

a single L293D driver IC can drive the rover. For this robot, beads affixed with glue

act as support wheels.

Fig.No 1.4 Construction8 DEPARTMENT OF ELECTRONICS MITS,

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1.7 PRINCIPLE USED :

Dual Tone Multi-Frequency, or DTMF, is a method for instructing a telephone switching

system of the telephone number to be dialled, or to issue commands to switching

systems or related telephony equipment.

It is perhaps the most widely known method of Multi Frequency Shift Keying

(MSFK) data transmission technique. It is used for telecommunication signalling over

analogue telephone lines in the voice-frequency band between telephone handsets and

other communications devices and the switching centre. These tones are then decoded

by the switching centre to determine which key was pressed.

In DTMF there are 16 distinct tones. Each tone is the sum of two frequencies: one from a

low and one from a high frequency group. There are four different frequencies in each

group.

Your phone only uses 12 of the possible 16 tones. If you look at your phone, there are

only 4 rows (R1, R2, R3 and R4) and 3 columns (C1, C2 and C3). The rows and

columns select frequencies from the low and high frequency group respectively. The

exact values of the frequencies are listed in Table below:9 DEPARTMENT OF ELECTRONICS MITS,

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DTMF keypad frequencies (with sound clips)1209 Hz 1336 Hz 1477 Hz 1633 Hz

697 Hz 1 2 3A

770 Hz 4 5 6B

852 Hz 7 8 9C

941 Hz * 0 #D

When used to dial a telephone number, pressing a single key will produce a pitch

consisting of two simultaneous pure tone sinusoidal frequencies. The row in which the

key appears determines the low frequency, and the column determines

the highfrequency. For example, pressing the '1' key will result in a sound composed

of both a 697 and a 1209 hertz.

The “*” is called the “star key” or “asterisk key”. “#” (while technically referred to as

“octothrope”) is called the “number sign”, “pound key”, or “hash key”, depending on

one's nationality or personal preference. These can be used for special functions.

In this project the robot, is controlled by a mobile phone that makes call to the mobile

phone attached to the robot in the course of the call, if any button is pressed control

corresponding to the button pressed is heard at the other end of the call. This tone is

called dual tone multi frequency tome (DTMF) robot receives this DTMF tone with

the help of phone stacked in the robot.10 DEPARTMENT OF ELECTRONICS MITS,


The received tone is processed by the microcontroller with the help of DTMF decoder

CM8870 the decoder decodes the DTMF tone in to its equivalent binary digit and this

binary number is send to the microcontroller, the microcontroller is programmed to

take a decision for any give input and outputs decision to motor drivers in order to

drive the motors for forward or backward motion or a turn. The mobile that makes a

call to the mobile phone stacked in the robot acts as a remote. So this simple robotic

project does not require the construction of receiver and transmitter units.

Enable pins (EN1 and EN2) of motor driver L293d respectively, to drive geared

motors. Switch S1 is used for manual reset.11 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


CHAPTER 2 2.1 BLOCK DIAGRAM:MOBILE

MOBILE

KEYPADTELEPHONIC

NETWORKMOBILE

MANUAL RECEIVING

SYSTEM DECODER

MICRO

CONTROLLER

MOTOR1

MOTOR

DRIVERSMOTOR2

Fig No. 2.1 Circuit working12 DEPARTMENT OF ELECTRONICS MITS,

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2.2DESCRIPTION :

The complete working of robot can be divided in the following blocks for easier

understanding:

Transmitting Cell phone (CT): It acts as a remote control of the robot. It remains with

the person who wishes to control the robot. Its purpose here is to generate the DTMF

tones corresponding to the number pressed on its keypad and transmit it thru the

mobile wireless network.

Fig no.2.2 .1 Cell phone

Receiving cell phone (CR): It receives the DTMF tones and forwards them to the

decoder thru its earphone plug outlet. In this project any common mobile can be used.

`

Decoder: It decodes the DTMF tones received into the corresponding keypad number.

This number is available in four bit binary format at some of its output pins. The

decoder used in this project is CM8870.

Microcontroller Block: Microcontroller takes this 4 bit numbers from decoder and

converts them to the corresponding signal that will be fed into the motor driver. The

microcontroller used in this project is AT89s8253.13 DEPARTMENT OF ELECTRONICS MITS,

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Motor Drivers: Motor Drivers take the TTL inputs from microcontroller and amplifies

their power to control the motors. The motor drivers used in this project are

L298/L293D.

Motors: They are the final mechanical part that which brings the motion to the robot.

Fig No. 2.2.2

Power supply block: This consist a Lead Acid Battery and a power regulator (7805) to

get 5v power supply. The 12V supply drives motor drivers and motors while the 5v

supply drives the microcontroller and the decoder.

Fig No.2.2.314 DEPARTMENT OF ELECTRONICS MITS,

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CHAPTER 3

KEY COMPONENTS:TYPE

COMPONENT QUANTITY

Transmitting cell phone

Any cell phone 1

Receiving cell phone

Any common NOKIA phone 1

Decoder

M8870 1

Microcontroller

AT89s8253 1

Motor Drivers

L298/l293d 1

Motor

12V DC Motors 2

Power supply

9V Lead Acid Battery 2

Voltage Regulator

7805 1

Table no.3.1

3.1 IC lMT8870 DTMF DECODER:

The M-8870 is a full DTMF Receiver that integrates both bandsplit filter and

decoder functions into a single 18-pin DIP or SOIC package. Manufactured using

CMOS process technology, the M-8870 offers low power consumption (35 mW max)

and precise data handling. Its filter section uses switched capacitor technology for

both the high and low group filters and for dial tone rejection. Its decoder uses digital

counting techniques to detect and decode all 16 DTMF tone pairs into a 4-bit code.

External component count is minimized by provision of an on-chip differential input

amplifier, clock generator, and latched tri-stateinterface bus. Minimal external

components required include a low-cost 3.579545 MHz color burst crystal, a timing

resistor, and a timing capacitor.

Design considerations:

The need of touch tone signaling frequencies to be in the voice band bring with it the

problem of vulnerability to talk-off which means that the speech signals may be

mistaken for touch tone signals and unwanted control actions such as terminating a

call may occur.15 DEPARTMENT OF ELECTRONICS MITS,


Another aspect of talk-off is that happens to talk, while signaling is being attempted.

The main design consideration for touch-tone signaling stem from the need for

protection against talk-offand include the following factors:

1.Choice of code

2.Band separation

3.Choice of frequencies

4.Choice of power levels

5.Signaling duration

In addition to these human factors and mechanical aspects also require consideration.

The choice of code for touchtone signaling should be Such that imitation of code

signals by speech and music should be difficult. Simple single frequency structures

are prone to east imitation as they occur frequently in speech Or Music. Hence some

form of multi frequency code is required. Such codes are easily derived by selecting

as set of N frequencies and restricting them in a binary fashion to being either present

or absent in a code combination. However some of the 2n combinations are not useful

as they contain only one frequency. Transmitting Simultaneously N frequencies

invoicing N-fold sharing of restricted amplitude range, and hence it is desirable to

keep as small as possible the number of frequencies to be transmitted simultaneously.

It is also advantageous to keep fixed the number of frequencies to be transmitted for

any valid code word. These factors lead to the consideration of p out of N code. Here

a combination of P frequencies out of N frequencies constitutes a code word.16 DEPARTMENT OF ELECTRONICS MITS,


Prior to touch-tone, P out of N Multi frequency signaling known as multi frequency

key pulsing (MFKP) was used between telephone exchanges by the operators. Here 2

or of 6 codes were used. This code is known to give a talk off performance of less

than I in 5000. However this degree to talk off performance is inadequate for

subscriber level signaling. In order to improve the performance, two measures are

adopted. Firstly while retaining P as two N is chosen to be seven or eight, depending

upon the number of code words desired. Secondly the chosen frequencies are placed

in two separate bands, and a restriction is applied such that one frequency from each

band is chosen to from a code word. When multiple frequencies are presented in

speech signals they are closely spaced. Band separation of touch-tone frequencies

reduces the probability of speech being able to produce touch-tone combinations. The

number o valid combination is now limited to N1*N2 where N1 & N2 represent the

number of frequencies in each band. With seven frequencies, four in one band and

three in the other we have 12 distinct signals as represented in the above fig. With

eight frequencies four in each band, we have 16 possible combinations. Since two

frequencies are mixed from a set of seven or eight frequencies, CCIT refers t touch

tone scheme by the name dual tone multi-frequencieshas the following advantages:

Band separation of two frequencies has the following advantages:

1.Before attempting to determine the two specific frequencies at the receiver end, band

filtering can be sued to separate the frequency groups. This renders determination of

specific frequencies simpler.

2.Each frequency component can be amplitude regulated separately.

3.Extreme instantaneous limiters, which are capable of providing substantial guard action,

can be used for each Frequency separately to reduce the probability of false response

to speech or other unwanted signals.

The choice of frequencies for touch-tone signaling is dictated by the attenuation and

delay distortion characteristics of telephone network circuits for the voice band

frequencies (300Hz340Hz). Frequencies in the range of 700-220Ohz. Both the lower

and the upper frequency band are defined in this range.17 DEPARTMENT OF ELECTRONICS MITS,


Having decided on the frequency band and the spacing, the specific Values of

frequencies can be so chosen as to avoid simple harmonic relationships like 1:2&2:3

between adjacent two frequencies in the same band and between pairs of frequencies

III two different bands, respectively. Such a selection improves talk off performance.

As mentioned earlier, sounds composed of a multiplicity of frequencies at comparable

levels are not likely to produce talk off because of limiter and selector design. Such

sounds are produced by consonants.

However vowels are single frequency sound with a series of harmonic components

present in them. Susceptibility to talk off due to vowelscanbe reduced by choosing the

specific frequencies appropriately.

The adjacent frequencies in the same band have a fixed ratio of 21: 19, I.e. only the

21” and 19t” harmonic components have the same frequency value. Across the bands,

the frequency that lie along the diagonals in above fig have ratio of 59:34. Thus

chosen frequency values are such that they almost eliminate talk off possibility due to

harmonics.

Since signaling information does not bear the redundancy of spoken words and

sentences it is desirable that the signals power be as large as possible. A nominal

value of 1 db above 1m W is provided for at telephone set for the combined signal

power of the two frequencies.

A major advantage of touch-tone dialing is the potential for data transmission and

remote control. The powerful application touch-tone dialing is data in voice answer

(DIVA) system.

The control unit can work in conjunction with either the signal from a remote FM

transmitter or a remote telephone. When a telephones, acts as the remote control unit,

the, telephone-lineinterfacing circuit come into operation as soon as ring is detected. It

consists of a ring detector that detects the ring form the exchange and triggers a timing

circuit. The output of the timer is given to a relay driver circuit in order to simulate

off- hook condition. The timer circuit maintains the telephone line in the off-

hook state for 1.518 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


minutes on detecting a ring from the exchange and connects the telephone line to the

DTMF decoding section though energized contacts of the relay.

The DTMF decoder uses IC MT8870, which forms a vital part of the circuit. It

converts the dual tones to corresponding binary outputs. A 4-to-16-line decoder

(74LS154) is used to convert the 4-0bit binary into 16 individual lines.

The output of the 4-to-16 line decoder is applied to the appliance on/off control circuit

that consists of AND gates and D flip-flops. The output of the on/off control circuit is

sued to control the required devices with the help of relays.

This circuit also provides a device status output that is used to enable a tone generator.

The short duration tone thus generated is transmitted through the telephone line by the

line interfacing circuit to inform the user about the resulting states of the controlled

device/appliance. TheM-8870-02 provides a “power-down” option which, when

enabled, drops consumption to less than 0.5 mW. The M-8870-02 can also inhibit the

decoding of fourth column digits.

.Pin Diagram:

Fig 3.1.1 Pin Diagram of IC1MT887019 DEPARTMENT OF ELECTRONICS MITS,

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Pin Functions of MT8870:

Table No.3.1.120 DEPARTMENT OF ELECTRONICS MITS,

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Tone Decoding of MT8870:

Table No.3.1.2

DTMF signaling:

AC register signaling is used in DTMF telephone. Here, tone rather then make/break

pulses, are use for dialing. Each dialed digit is unique represented by a pair of sine

wave tone. These tones (one form low ground for row and another from high group

column) are sent to the exchange when a digit is dialed by pushing the key. These

tones lie within the speech band 300 to 340Ohz, and are chosen so as minimize the

possibility of any21 DEPARTMENT OF ELECTRONICS MITS,


valid frequency pair existing in the normal speech simultaneously. Actually, this

minimization is made possible by forming pairs with one tone from the higher group

and the other from lower group frequency. The DTMF spectrum is shown in fig.

A valid DTMF signal is the sum of the tones, one from a lower group (697 Hz) and

the other form a higher group (1209-1663 Hz). Each group constrains one individual

tone. The DTMF dialing scheme is shown in fig. This scheme allows unique

combination. Ten of these represent digits I through 9 and 0. The remaining 6 digit are

reserved fro special- purpose dialing.

Tones in DTMF dialing are so choose that none of the tones is harmonic of another

tone. Therefore there is no chance of distortion caused by harmonics. This tone is sent

as long as the key remains pressed.

The DTMF coding scheme ensures that each signal contains only one component

form each of the low and high groups. This significantly simplifies decoding because

the composite DTMF signals may be separated with band-pass filters into single

frequency component, each of which may be handled individually. As a result, the

DTMF coding scheme is a flexible signaling scheme with high reliability, hence

motivating innovative and competitive decoder design.

Features of DTMF decoder

Complete DTMF Receiver

Low power consumption

Internal gain setting amplifier

Adjustable guard time

Central office quality

Power-down mode

Inhibit mode

Backward compatible with MT8870C/MT887OC – I22 DEPARTMENT OF ELECTRONICS MITS,

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Typical Applications for DTMF decoders

Paging systems

Repeater systems/mobile radio

Credit card systems

Remote control

Personal computers

DTMF SIGNALING23 DEPARTMENT OF ELECTRONICS MITS,

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3.2 MICROCONTROLLER DETAILS:

The microcontroller used here is a common 8 bit Atmel microcontroller AT89s8253.It

is alow-power, high-performance CMOS 8-bit microcontroller with12K bytes of In-

SystemProgrammable (ISP) Flash program memory and 2K bytes of EEPROM data

memory. It has 32 programmable input output lines.

Features:

• 12K Bytes of In-System Programmable (ISP) Flash Program Memory

–SPI Serial Interface for Program Downloading

–Endurance: 10,000 Write/Erase Cycles

• 2K Bytes EEPROM Data Memory

– Endurance: 100,000 Write/Erase Cycles

•2.7V to 5.5V Operating Range

•Fully Static Operation: 0 Hz to 24 MHz (in x1 and x2 Modes)

F

Fig No.3.2.1 pin Diagram of24 DEPARTMENT OF ELECTRONICS MITS,


•Three-level Program Memory Lock

•256 x 8-bit Internal RAM

•32 Programmable I/O Lines

•Three 16-bit Timer/Counters

•Nine Interrupt Sources

•Enhanced UART Serial Port with Framing Error Detection and Automatic Address

Recognition

•Enhanced SPI (Double Write/Read Buffered) Serial Interface

•Programmable Watchdog Timer

1.Description

The AT89S8253 is a low-power, high-performance CMOS 8-bit microcontroller with

12K bytes of In-System Programmable (ISP) Flash program memory and 2K bytes of

EEPROM data memory. The device is manufactured using Atmel’s high-density non-

volatile memory technology and is compatible with the industry-standard MCS-

51 instruction set and pinout. The on-chip downloadable Flash allows the program

memory to be reprogrammed in- system through an SPI serial interface or by a

conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU

with downloadable Flash on a monolithic chip, the Atmel AT89S8253 is a powerful

microcontroller which provides a highly-flexible and cost-effectivesolution to many

embedded control applications.

The AT89S8253 provides the following standard features: 12K bytes of In-

SystemProgrammable Flash, 2K bytes of EEPROM, 256 bytes of RAM, 32 I/O lines,

programmable watchdog timer, two data pointers, three 16-bit timer/counters, a six-

vector, four-levelinterrupt architecture, a full duplex serial port, on-chip oscillator, and

clock circuitry. In addition, the AT89S8253 is designed with static logic for operation

down to zero frequency and supports two software selectable power saving modes.

The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port,

and interrupt system to continue functioning. The Power-down mode saves the RAM

contents but freezes the oscillator, disabling all other chip functions until the next

external interrupt or hardware reset.25 DEPARTMENT OF ELECTRONICS MITS,

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The on-board Flash/EEPROM is accessible through the SPI serial interface. Holding

RESET active forces the SPI bus into a serial programming interface and allows the

program memory to be written to or read from, unless one or more lock bits have been

activated.

Pin description :

VCC : Supply voltage (all packages except 42-PDIP).

GND: Ground (all packages except 42-PDIP; for 42-PDIP GND connects only the

logic core and the embedded program/data memories).

VDD: Supply voltage for the 42-PDIP which connects only the logic core and the

embedded program/data memories

PWRVDD: Supply voltage for the 42-PDIP which connects only the I/O Pad Drivers.

The application board must connect both VDD and PWRVDD to the board supply

voltage

PWRGND: Ground for the 42-PDIP which connects only the I/O Pad Drivers.

PWRGND and GND are weakly connected through the common silicon substrate, but

not through any metal links. The application board must connect both GND and

PWRGND to the board ground

PORT0: Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each

pin can sink six TTL inputs. When 1s are written to port 0 pins, the pins can be used

as high- impedance inputs. Port 0 can also be configured to be the multiplexed low-

order address/data bus during accesses to external program and data memory. In this

mode, P0 has internalpull-ups.

Port 0 also receives the code bytes during Flash programming and outputs the code

bytes during program verification. External pull-ups are required during

program

verification.26 DEPARTMENT OF ELECTRONICS MITS,

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PORT 1 :

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output

buffers can sink/source six TTL inputs.

When 1s are written to Port 1 pins, they are pulled high by the weak internal pull-

ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled

low will source current (IL,150 µA typical) because of the weak internal pull-ups.

Some Port 1 pins provide additional functions. P1.0 and P1.1 can be configured to be

the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2 trigger

input (P1.1/T2EX), respectively. Furthermore, P1.4, P1.5, P1.6, and P1.7 can be

configured as the SPI slave port select, data input/output.

PORT 2 :


buffers can sink/source six TTL inputs. When 1s are written to Port 2 pins, they are

pulled high by the weak internal pull-ups and can be used as inputs. As inputs, Port 2

pins that are externally being pulled low will source current (IL,150 µA typical)

because of the weak internal pull-ups.

Port 2 emits the high-order address byte during fetches from external program

memory and during accesses to external data memory that use 16-bit addresses

(MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when

emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX

@ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also

receives the high-order address bits and some control signals during Flash

programming and verification.27 DEPARTMENT OF ELECTRONICS MITS,

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PORT 3 :


buffers can sink/source six TTL inputs. When 1s are written to Port 3 pins, they are

pulled high by the weak internal pull-ups and can be used as inputs. As inputs, Port 3

pins that are externally being pulled low will source current (IIL,150 µA typical)

because of the weak internal pull-ups.Port 3 receives some control signals for Flash

programming and verification.Port Pin Alternate FunctionsP3.0 RXD (serial input port)P3.1 TXD (serial output port)P3.2 INT0 (external interrupt 0)(1)

P3.3 INT1 (external interrupt 1)(1)

P3.4 T0 (timer 0 external input)P3.5 T1 (timer 1 external input)P3.6 WR (external data memory write strobe)P3.7 RD (external data memory read strobe)

RESET:

Reset input. A high on this pin for at least two machine cycles while the oscillator is

running resets the device

PSEN

Program Store Enable. PSEN is the read strobe to external program memory (active

low). When the AT89S8253 is executing code from external program memory, PSEN

is activated twice each machine cycle, except that two PSEN activations are skipped

during each access to external data memory

28 DEPARTMENT OF ELECTRONICS MITS, LUCKNOW


Special Function Registers

A map of the on-chip memory area called the Special Function Register (SFR) .

Note that not all of the addresses are occupied, and unoccupied addresses may not be

implemented on the chip. Read accesses to these addresses will generally return

random data, and write accesses will have an indeterminate effect.

User software should not write 1s to these unlisted locations, since they may be used

in future products to invoke new features. In that case, the reset or inactive values of

the new bits will always be 0.29 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


In this project the microcontroller block performs the following tasks:KEY(on cell phone)

DATA(4 bit binary ACTION

format)

2

0010

M1=forward M2=forward

4

0100

M1=backward M2=forward

6

0110

M1=forward M2=backward

8

1000

M1=backward

M2=backward

5

0101

M1=halt M2=halt

Table No. 3.2.1

PIN CONFIGURATION:

KEY

PIN NUMBER

Motor 1 output

P2.1

Motor 1 Output

P2.2

Motor 2 Output

P2.4

Motor 2 Output

P2.5

Decoder Input 1

P1.1

Decoder Input 2

P1.2

Decoder Input 3

P1.3

Decoder Input 4

P1.4

Table No.3.2.230 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


3.3 DC MOTOR :

A DC motor is designed to run on DC electric power. Two examples of pure DC

designs areMichael Faraday's homopolar motor (which is uncommon), and the ball

bearing motor, which is (so far) a novelty. By far the most common DC motor types

are the brushed and brushless types, which use internal and external commutation

respectively to create an oscillating AC current from the DC source—so they are not

purely DC machines in a strict sense.

Brushed DC motor

The classic DC motor design generates an oscillating current in a wound rotor,

or armature, with a split ring commutator, and either a wound or permanent magnet

stator. A rotor consists of one or more coils of wire wound around a core on a shaft;

an electrical power source is connected to the rotor coil through the commutator and

its brushes, causing current to flow in it, producing

Fig No. 3.3.131 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


electromagnetism. The commutator causes the current in the coils to be switched as

the rotor turns, keeping the magnetic poles of the rotor from ever fully aligning with

the magnetic poles of the stator field, so that the rotor never stops (like a compass

needle does) but rather keeps rotating indefinitely (as long as power is applied and is

sufficient for the motor to overcome the shaft torque load and internal losses due to

friction, etc.)

Many of the limitations of the classic commutator DC motor are due to the need for

brushes to press against the commutator. This creates friction. At higher speeds,

brushes have increasing difficulty in maintaining contact. Brushes may bounce off the

irregularities in the commutator surface, creating sparks. (Sparks are also created

inevitably by the brushes making and breaking circuits through the rotor coils as the

brushes cross the insulating gaps between commutator sections. Depending on the

commutator design, this may include the brushes shorting together adjacent sections

— and hence coil ends—momentarily while crossing the gaps. Furthermore,

the inductance of the rotor coils causes the voltage across each to rise when its circuit

is opened, increasing the sparking of the brushes.) This sparking limits the maximum

speed of the machine, as too-rapid sparking will overheat, erode, or even melt the

commutator. The current density per unit area of the brushes, in combination with

their resistivity, limits the output of the motor. The making and breaking of electric

contact also causes electrical noise,and the sparks additionally cause RFI. Brushes

eventually wear out and require replacement, and the commutator itself is subject to

wear and maintenance (on larger motors) or replacement (on small motors). The

commutator assembly on a large machine is a costly element, requiring precision

assembly of many parts. On small motors, the commutator is usually permanently

integrated into the rotor, so replacing it usually requires replacing the whole rotor.32 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Large brushes are desired for a larger brush contact area to maximize motor output,

but small brushes are desired for low mass to maximize the speed at which the motor

can run without the brushes excessively bouncing and sparking (comparable to the

problem of "valve float" in internal combustion engines). (Small brushes are also

desirable for lower cost.) Stiffer brush springs can also be used to make brushes of a

given mass work at a higher speed, but at the cost of greater friction losses (lower

efficiency) and accelerated brush and commutator wear. Therefore, DC motor brush

design entails a trade-off between output power, speed, and efficiency.

A:shunt

B:series

C:compound f = field coil

Brushless DC motors

Some of the problems of the brushed DC motor are eliminated in the brushless design.

In this motor, the mechanical "rotating switch" or commutator/brushgear assembly is

replaced by an external electronic switch synchronised to the rotor's position.

Brushless motors are typically85-90% efficient or more (higher efficiency for a

brushless electric motor of up to 96.5% were reported by researchers at the Tokai

University in Japan in 2009),[14] whereas DC motors with brushgear are typically 75-

80% efficient.33 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Fig No.3.3.2

Midway between ordinary DC motors and stepper motors lies the realm of

the brushless DC motor. Built in a fashion very similar to stepper motors, these often

use a permanent magnet external rotor, three phases of driving coils, one or more Hall

effect sensors to sense the position of the rotor, and the associated drive electronics.

The coils are activated, one phase after the other, by the drive electronics as cued by

the signals from either Hall effect sensors or from the back EMF (electromotive

force) of the undriven coils. In effect, they act asthree-phase synchronous motors

containing their own variable- frequency drive electronics. A specialized class of

brushless DC motor controllers utilize EMF feedback through the main phase

connections instead of Hall effect sensors to determine position and velocity. These

motors are used extensively in electric radio- controlled vehicles. When configured

with the magnets on the outside, these are referred to by mode lists as out runner

motors.

Brushless DC motors are commonly used where precise speed control is necessary, as incomputer disk drives or in video cassette recorders, the spindles within CD, CD-

ROM (etc.) drives, and mechanisms within office products such as fans, laser

printers and photocopiers. They have several advantages over conventional motors:

Compared to AC fans using shaded-pole motors, they are very efficient, running much

cooler than the equivalent AC motors. This cool operation leads to much- improved

life of the fan's bearings.34 DEPARTMENT OF ELECTRONICS MITS,


Without a commutator to wear out, the life of a DC brushless motor can be significantly

longer compared to a DC motor using brushes and a commutator. Commutation also

tends to cause a great deal of electrical and RF noise; without a commutator or

brushes, a brushless motor may be used in electrically sensitive devices like audio

equipment or computers.

The same Hall effect sensors that provide the commutation can also provide a

convenienttachometer signal for closed-loop control (servo-controlled) applications.

In fans, the tachometer signal can be used to derive a "fan OK" signal.

The motor can be easily synchronized to an internal or external clock, leading to precise

speed control.

Brushless motors have no chance of sparking, unlike brushed motors, making them

better suited to environments with volatile chemicals and fuels. Also, sparking

generates ozone which can accumulate in poorly ventilated buildings risking harm to

occupants' health.

Brushless motors are usually used in small equipment such as computers and are

generally used to get rid of unwanted heat.

They are also very quiet motors which is an advantage if being used in equipment that is

affected by vibrations.

Modern DC brushless motors range in power from a fraction of a watt to many

kilowatts. Larger brushless motors up to about 100 kW rating are used in electric

vehicles. They also find significant use in high-performance electric model aircraft.

Coreless or ironless DC motors

Nothing in the design of any of the motors described above requires that the iron

(steel) portions of the rotor actually rotate; torque is exerted only on the windings of

the electromagnets. Taking advantage of this fact is the coreless or ironless DC

motor, a specialized form of a brush or brushless DC motor. Optimized for

rapid acceleration, these motors have a rotor that is constructed without any iron core.

The rotor can take the form of a winding-filled cylinder, or aself-supporting structure

comprising only the magnet wire and the bonding material. The rotor can fit inside

the stator magnets; a35 DEPARTMENT OF ELECTRONICS MITS,


magnetically-soft stationary cylinder inside the rotor provides a return path for the

stator magnetic flux. A second arrangement has the rotor winding basket surrounding

the stator magnets. In that design, the rotor fits inside a magnetically-soft cylinder that

can serve as the housing for the motor, and likewise provides a return path for the

flux.

Because the rotor is much lighter in weight (mass) than a conventional rotor formed

from copperwindings on steel laminations, the rotor can accelerate much more

rapidly, often achieving a mechanical time constant under 1 ms. This is especially true

if the windings use aluminum rather than the heavier copper. But because there is no

metal mass in the rotor to act as a heat sink, even small coreless motors must often be

cooled by forced air. Related limited-travel actuators have no core and a bonded coil

placed between the poles of high-flux thin permanent magnets. These are the fast head

positioners for rigid-disk ("hard disk") drives.

Printed Armature or Pancake DC Motors

A rather unique motor design the pancake/printed armature motor has the windings

shaped as a disc running between arrays of high-flux magnets, arranged in a circle,

facing the rotor and forming an axial air gap. This design is commonly known the

pancake motor because of its extremely flat profile, although the technology has had

many brand names since it's inception, such as ServoDisc.

The printed armature (originally formed on a printed circuit board) in a printed

armature motor is made from punched copper sheets that are laminated together using

advanced composites to form a thin rigid disc. The printed armature has a unique

construction, in the brushed motor world, in that is does not have a separate ring

commutator. The brushes run directly on the armature surface making the whole

design very compact.

An alternative manufacturing method is to use wound copper wire laid flat with a

central conventional commutator, in a flower and petal shape. The windings are

typically stabilized by being impregnated with electrical epoxy potting systems. These

are filled epoxies that have moderate mixed viscosity and a long gel time. They are

highlighted by low shrinkage and low exothermal, and are typically UL 1446

recognized as a potting compound for use up to 180°C.36 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


3.4 POWER SUPPLY UNIT (+5V)

Power supplies are designed to convert high voltage AC mains electricity to a suitable

low voltage supply for electronics circuits and other devices. A power supply can by

broken down into a series of blocks, each of which performs a particular function.

For a 5V regulated supply :

Fig. No.3.4.1

Each of the block has its own function as described below

Transformer – steps down high voltage AC mains to low voltage AC.

Rectifier – converts AC to DC, but the DC output is varying.

Smoothing – smooths the DC from varying greatly to a small ripple.

Regulator – eliminates ripple by setting DC output to a fixed voltage.

TRANSFORMER:

Transformers convert AC electricity from one voltage to another with little loss of

power. Transformers work only with AC and this is one of the reasons why mains

electricity is AC. The two types of transformers

Step-up transformers increase voltage,

Step-down transformers reduce voltage.37 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Fig. no.3.4.2 Transformer

Most power supplies use a step-down transformer to reduce the dangerously

high mains voltage (230V in UK) to a safer low voltage. The input coil is called

the primary and the output coil is called the secondary. There is no electrical

connection between the two coils, instead they are linked by an alternating magnetic

field created in thesoft-iron core of the transformer. The two lines in the middle of the

circuit symbol represent the core.

Transformers waste very little power so the power out is (almost) equal to the power

in. Note that as voltage is stepped down current is stepped up. The ratio of the number

of turns on each coil, called the turns ratio, determines the ratio of the voltages.

A step-down transformer has a large number of turns on its primary (input) coil which

is connected to the high voltage mains supply, and a small number of turns on its

secondary (output) coil to give a low output voltage.Turns ratio = Vp = Np

Vs Ns

And Power Out = Power In

Vs Is Vp Ip

Where

Vp = primary (input) voltage

Np = number of turns on primary coil

Ip = primary (input) current

Ns = number of turns on secondary coil38 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Is = secondary (output) current

Vs = secondary (output) voltage

RECTIFIER:

A bridge rectifier can be made using four individual diodes, but it is also available in

special packages containing the four diodes required. It is called a full-wave rectifier

because it uses all the AC wave (both positive and negative sections). 1.4V is used up

in the bridge rectifier because each diode uses 0.7V when conducting and there are

always two diodes conducting, as shown in the diagram below. Bridge rectifiers are

rated by the maximum current they can pass and the maximum reverse voltage they

can withstand (this must be at least three times the supply RMS voltage so the rectifier

can withstand the peak voltages). Please see the DIODESpage for more details,

including pictures of bridge rectifiers. In this alternate pairs of diodes conduct,

changing over the connections so the alternating directions of AC are converted to the

one direction of DC.

Fig. No.3.4.3 OUTPUT – Full-wave Varying DC

SMOOTHING:

Smoothing is performed by a large value electrolytic capacitor connected across the

DC supply to act as a reservoir, supplying current to the output when the varying DC

voltage from the rectifier is falling. The diagram shows the unsmoothed varying DC

(dotted line) and the smoothed DC (solid line). The capacitor charges quickly near the39 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


peak of the varying DC, and then discharges as it supplies current to the output.

Fig.No.3.4.4 Capacitor Voltage

Note that smoothing significantly increases the average DC voltage to almost the

peak value (1.4 × RMS value). For example 6V RMS AC is rectified to full wave DC

of about 4.6V RMS (1.4V is lost in the bridge rectifier), with smoothing this

increases to almost the peak value giving 1.4 × 4.6 = 6.4V smooth DC.

Smoothing is not perfect due to the capacitor voltage falling a little as it discharges,

giving a small ripple voltage. For many circuits a ripple which is 10% of the supply

voltage is satisfactory and the equation below gives the required value for the

smoothing capacitor. A larger capacitor will give less ripple. The capacitor value must

be doubled when smoothing half-wave DC.

Smoothing capacitor for 10% ripple

, C = 5 × Io

Vs × f

Where,

C = smoothing capacitance in farads (F)

Io = output current from the supply in amps (A)

Vs = supply voltage in volts (V), this is the peak value of the unsmoothed DC

f = frequency of the AC supply in hertz (Hz), 50Hz in the UK40 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


REGULATOR:

Regulator

Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or

variable output voltages. They are also rated by the maximum current they can pass.

Negative voltage regulators are available, mainly for use in dual supplies. Most

regulators include some automatic protection from excessive current ( 'overload

protection') and overheating ( 'thermal protection'). Many of the fixed voltage

regulator ICs have 3 leads and look like power transistors, such as the 7805 +5V 1A

regulator shown on the right. They include a hole for attaching a heatsink if necessary.

Working Of Power Supply

Transformer

Fig.No.3.4.5 Transformer Output

The low voltage AC output is suitable for lamps, heaters and special AC motors. It

is notsuitable for electronic circuits unless they include a rectifier and a smoothing

capacitor.41 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Transformer + Rectifier

Fig. No.3.4.6 Rectifier Stage Output

The varying DC output is suitable for lamps, heaters and standard motors. It

is not suitable for electronic circuits unless they include a smoothing capacitor.

Transformer + Rectifier + Smoothing

Fig.No.3.4.7 Filtered Output42 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


3.5 Resistor:

A resistor is a two-terminal passive electronic component which implements electrical

resistance as a circuit element. When a voltage V is applied across the terminals of a

resistor, a current I will flow through the resistor in direct proportion to that voltage.

The reciprocal of the constant of proportionality is known as the resistance R, since,

with a given voltage V, a larger value of R further "resists" the flow of current I as

given by Ohm's law:

Fig. 3.5.1 Resistor

Resistors are common elements of electrical networks and electronic circuits and are

ubiquitous in most electronic equipment. Practical resistors can be made of various

compounds and films, as well as resistance wire (wire made of a high-resistivity alloy,

such as nickel-chrome).Resistors are also implemented within integrated circuits,

particularly analog devices, and can also be integrated into hybrid and printed circuits.

The electrical functionality of a resistor is specified by its resistance: common

commercial resistors are manufactured over a range of more than 9 orders of

magnitude. When specifying that resistance in an electronic design, the required

precision of the resistance may require attention to the manufacturing tolerance of the

chosen resistor, according to its specific application.43 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Fig. 3.5.2 Carbon Film Resistor

The temperature coefficient of the resistance may also be of concern in some

precision applications. Practical resistors are also specified as having a maximum

power rating which must exceed the anticipated power dissipation of that resistor in a

particular circuit: this is mainly of concern in power electronics applications. Resistors

with higher power ratings are physically larger and may require heat sinking. In a high

voltage circuit, attention must sometimes be paid to the rated maximum working

voltage of the resistor.

The series inductance of a practical resistor causes its behavior to depart from ohms

law; this specification can be important in some high-frequency applications for

smaller values of resistance. In a low-noise amplifier or pre-amp the noise

characteristics of a resistor may be an issue. The unwanted inductance, excess noise,

and temperature coefficient are mainly dependent on the technology used in

manufacturing the resistor. They are not normally specified individually for a

particular family of resistors manufactured using a particular technology.[1] A family

of discrete resistors is also characterized according to its form factor, that is, the size

of the device and position of its leads (or terminals) which is relevant in the practical

manufacturing of circuits using them.

Fig No.3.5.3



The resistance value is displayed using the color code ( the colored bars/the colored

stripes ), because the average resistor is too small to have the value printed on it with

numbers. You had better learn the color code, because almost all resistors of 1/2W or

less use the color-code to display the resistance value.45 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


3.6 Capacitor :

The capacitor's function is to store electricity, or electrical energy. The capacitor also

functions as a filter, passing alternating current (AC), and blocking direct current

(DC). This symbol is used to indicate a capacitor in a circuit diagram . The

capacitor is constructed with two electrode plates facing eachother, but separated by

an insulator.

When DC voltage is applied to the capacitor, an electric charge is stored on each

electrode. While the capacitor is charging up, current flows.The current will stop

flowing When a circuit tester, such as an analog meter set to measure resistance, is

connected to a 10 microfarad (µF) electrolytic capacitor, a current will flow, but only

for a moment. You can confirm that the meter's needle moves off of zero, but returns

to zero right away. When you connect the meter's probes to the capacitor in reverse,

you will note that current once again flows for a moment. Once again, when the

capacitor has fully charged, the current stops flowing. So the capacitor can be used as

a filter that blocks DC current. However, in the case of alternating current, the current

will be allowed to pass. Alternating current is similar to repeatedly switching the test

meter's probes back and forth on the capacitor. Current flows every time the probes

are switched. When it works.

The value of a capacitor (the capacitance), is designated in units called the Farad ( F ).

The capacitance of a capacitor is generally very small, so units such as the microfarad

(10-6F),nanofarad(10-9F),andpicofarad(10-12F)areused .Recently, an new capacitor

with

very high capacitance has been developed. The Electric Double Layer capacitor has

capacitance designated in Farad units. This is new capacitor.

Sometimes, a three-digit code is used to indicate the value of a capacitor. There are

two ways in which the capacitance can be written. One uses letters and numbers, the

other uses only numbers. In either case, there are only three characters used. [10n] and

[103] denote the same value of capacitance. The method used differs depending on the46 DEPARTMENT OF ELECTRONICS MITS,


capacitor supplier. In the case that the value is displayed with the three-digit code, the

1st and 2nd digits from the left show the 1st figure and the 2nd figure, and the 3rd

digit is a multiplier which determines how many zeros are to be added to the

capacitance. The capacitor has an insulator( the dielectric ) between 2 sheets

of electrodes. Different kinds of capacitors use different materials for the dielectric.

Breakdown voltage When using a capacitor, you must pay attention to the maximum

voltage which can be used. This is the "breakdown voltage." The breakdown voltage

depends on the kind of capacitor being used. You must be especially careful with

electrolytic capacitors because the breakdown voltage is comparatively low. The

breakdown voltage of electrolytic capacitors is displayed as Working Voltage. The

breakdown voltage is the voltage that when exceeded will cause the dielectric

(insulator) inside the capacitor to break down and conduct. When this happens, the

failure can be catastrophic. I will introduce the different types of capacitors below.

Electrolytic Capacitors (Electrochemical type capacitors) Aluminum is used for the

electrodes by using a thin oxidization membrane. Large values of capacitance can be

obtained in comparison with the size of the capacitor, because the dielectric used is

very thin. The most important characteristic of electrolytic capacitors is that they have

polarity.

They have a positive and a negative electrode.[Polarised] This means that it is very

important which way round they are connected. If the capacitor is subjected to voltage

exceeding its working voltage, or if it is connected with incorrect polarity, it may

burst. It is extremely dangerous, because it can quite literally explode. Make

absolutely no mistakes.

Multilayer Ceramic Capacitor

The multilayer ceramic capacitor has a many-layered dielectric. These capacitors are

small in size, and have good temperature and frequency characteristics. Square wave

signals used in digital circuits can have a comparatively high frequency

component included .This capacitor is used to bypass the high frequency to ground.



Fig No.3.6.1 Capacitor

Generally, in the circuit diagram, the positive side is indicated by a "+" (plus) symbol.

Electrolytic capacitors range in value from about 1µF to thousands of µF. Mainly this

type of capacitor is used as a ripple filter in a power supply circuit, or as a filter to

bypass low frequency signals, etc. Because this type of capacitor is comparatively

similar to the nature of a coil in construction, it isn't possible to use for high-frequency

circuits. (It is said that the frequency characteristic is bad.)

The photograph on the left is an example of the different values of electrolyticcapacitors in which thecapacitance and voltagediffer.

From

the

left

to

right:

1µF (50V) [diameter 5

mm, high 12 mm]

47µF (16V) [diameter 6 mm, high 5 mm]




The size of the capacitor sometimes depends on the manufacturer. So the sizes shown48 DEPARTMENT OF ELECTRONICS MITS,


here on this page are just examples. In the photograph to the right, the mark indicating

the negative lead of the component can be seen. You need to pay attention to the

polarity indication so as not to make a mistake when you assemble the circuit.

TantalumCapacitors

Tantalum Capacitors are electrolytic capacitors that is use a material called tantalum

for the electrodes. Large values of capacitance similar to aluminum electrolytic

capacitors can be obtained. Also, tantalum capacitors are superior to aluminum

electrolytic capacitors in temperature and frequency characteristics. When tantalum

powder is baked in order to solidify it, a crack forms inside. An electric charge can be

stored . These capacitors have polarity as well. Usually, the "+" symbol is used to

show the positive component lead. Do not make a mistake with the polarity on these

types. Tantalum capacitors are a little bit more expensive than aluminum electrolytic

capacitors. Capacitance can change with temperature as well as frequency, and these

types are very stable. Therefore, tantalum capacitors are used for circuits which

demand high stability in the capacitance values. Also, it is said to be common sense to

use tantalum capacitors for analog signal systems, because the current-spike noise that

occurs with aluminum electrolytic capacitors does not appear.

Ceramic Capacitor

Ceramic capacitors are constructed with materials such as titanium acid barium used

as the dielectric. Internally, these capacitors are not constructed as a coil, so they can

be used in high frequency applications. Typically, they are used in circuits which

bypass high frequency to ground. These capacitors have the shape of a disk. The

capacitor on the left is a 100pF capacitor with a diameter of about 3 mm. The

capacitor on the right side is printed with 103, so 10 x 103pF becomes 0.01 µF.49 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


In the photograph, the capacitance of the component on the left is displayed as 104.

So, the capacitance is 10 x 104 pF = 0.1 µF. The thickness is 2 mm, the height is 3

mm, the

width is 4mm .The capacitor to the right has a capacitance of 103 (10 x 103 pF = 0.01

µF). The heightis 4 mm, the diameter of the round part is 2 mm.

These capacitorsare not polarized. That is, they have no polarity.

Polystyrene Film Capacitors

In these devices, polystyrene film is used as the dielectric. This type of capacitor is

not for use in high frequency circuits, because they are constructed like a coil inside.

They are used well in filter circuits or timing circuits which run at several hundred

KHz or less.

The component shown on the left has a red color due to the copper leaf used for the

electrode. The silver color is due to the use of aluminum foil as the electrode. The

device on the left has a height of 10 mm, is 5 mm thick, and is rated 100pF. The

device in the middle has a height of 10 mm, 5.7 mm thickness, and is rated 1000pF.

The device on the right has a height of 24 mm, is 10 mm thick, and is rated 10000pF.

Electric Double Layer Capacitors (Super Capacitors)

This is a "Super Capacitor," which is quite a wonder. The capacitance is

0.47F(470,000 µF). I have not used this capacitor in an actual circuit.50 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Care must be taken when using a capacitor with such a large capacitance in power

supply circuits, etc. The rectifier in the circuit can be destroyed by a huge rush of

current when the capacitor is empty. For a brief moment, the capacitor is more like a

short circuit. A protection circuit needs to be set up.

The size is small in spite of capacitance. Physically, the diameter is 21 mm, the height

is 11 mm.

Care is necessary, because these devices do have polarity.

Polyester Film Capacitors

This capacitor uses thin polyester film as the dielectric.

They are not high tolerance, but they are cheap and handy. Their tolerance is about

±5% to ±10%.

From the left in the photograph

Capacitance: 0.001 µF (printed with 001K)

[the width 5 mm, the height 10 mm, the thickness 2 mm] Capacitance: 0.1 µF (printed

with 104K)

[the width 10 mm, the height 11 mm, the thickness 5mm] Capacitance: 0.22 µF

(printed with .22K)

[the width 13 mm, the height 18 mm, the thickness 7mm]

Care must be taken, because different manufacturers use different methods to denote51 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


the capacitance values.

Here are some other polyester film capacitors.

Starting from the left

Capacitance: 0.0047 µF (printed with 472K)

[the width 4mm, the height 6mm, the thickness 2mm] Capacitance: 0.0068 µF

(printed with 682K)

[the width 4mm, the height 6mm, the thickness 2mm] Capacitance: 0.47 µF (printed

with 474K)

[the width 11mm, the height 14mm, the thickness 7mm] These capacitors have no

polarity.

Polypropylene Capacitors

This capacitor is used when a higher tolerance is necessary than polyester capacitors

offer. Polypropylene film is used for the dielectric. It is said that there is almost no

change of capacitance in these devices if they are used with frequencies of 100KHz or

less.

The pictured capacitors have a tolerance of ±1%.

From the left in the photograph Capacitance: 0.01 µF (printed with 103F) [the width

7mm, the height 7mm, the thickness 3mm]52 DEPARTMENT OF ELECTRONICS MITS,


Capacitance: 0.022 µF (printed with 223F)

[the width 7mm, the height 10mm, the thickness 4mm] Capacitance: 0.1 µF (printed

with 104F)

[the width 9mm, the height 11mm, the thickness 5mm]

When I measured the capacitance of a 0.01 µF capacitor with the meter which I have,

the error was +0.2%.

These capacitors have no polarity.

Mica Capacitors

These capacitors use Mica for the dielectric. Mica capacitors have good stability

because their temperature coefficient is small. Because their frequency characteristic

is excellent, they are used for resonance circuits, and high frequency filters. Also, they

have good insulation, and so can be utilized in high voltage circuits. It was often used

for vacuum tube style radio transmitters, etc. Mica capacitors do not have high values

of capacitance, and they can be relatively expensive.

VariableCapacitors

Variable capacitors are used for adjustment etc. of frequency mainly.

On the left in the photograph is a "trimmer," which uses ceramic as the dielectric. Next

to it on the right is one that uses polyester film for the dielectric.

The pictured components are meant to be mounted on a printed circuit board. When

adjusting the value of a variable capacitor, it is advisable to be careful. One of the

component's leads is connected to the adjustment screw of the capacitor. This means

that the value of the capacitor can be affected by the capacitance of the screwdriver in

your hand. It is better to use a special screwdriver to adjust these components.

A capacitor (formerly known as condenser) is a device for storing electric charge. The

forms of practical capacitors vary widely, but all contain at least two conductors

separated by anon-conductor. Capacitors used as parts of electrical systems, for

example, consist of metal foils separated by a layer of insulating film.53 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Fig.No. 3.6..2 Carbon Film capacitor

A capacitor is a passive electronic component consisting of a pair of conductors

separated by a dielectric (insulator). When there is a potential difference (voltage)

across the conductors, a static electric field develops across the dielectric, causing

positive charge to collect on one plate and negative charge on the other plate. Energy

is stored in the electrostatic field. An ideal capacitor is characterized by a single

constant value, capacitance, measured in farads. This is the ratio of the electric charge

on each conductor to the potential difference between them.

Capacitors are widely used in electronic circuits for blocking direct current while

allowing alternating current to pass, in filter networks, for smoothing the output of

power supplies, in the resonant circuits that tune radios to particular frequencies and

for many other purposes.

The capacitance is greatest when there is a narrow separation between large areas of

conductor, hence capacitor conductors are often called "plates", referring to an early

means of construction. In practice the dielectric between the plates passes a small

amount of leakage current and also has an electric field strength limit, resulting in a

breakdown voltage, while the conductors and leads introduce an undesired inductance

and resistance.54 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


3.7 Crystal Oscillator :

A crystal oscillator is an electronic oscillator circuit that uses the mechanical

resonance of a vibrating crystal of piezoelectric material to create an electrical signal

with a very precise frequency. This frequency is commonly used to keep track of time

(as in quartz wristwatches), to provide a stable clock signal for digital integrated

circuits, and to stabilize frequencies for radio transmitters and receivers. The most

common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits

designed around them became known as "crystal oscillators."

Fig.3.7.1 Crystal Oscillator

Quartz crystals are manufactured for frequencies from a few tens of kilohertz to tens

of megahertz. More than two billion (2×109) crystals are manufactured annually.

Most are used for consumer devices such as wristwatches, clocks, radios, computers,

and cellphones. Quartz crystals are also found inside test and measurement

equipment, such as counters, signal generators, and oscilloscopes.

Operation

A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a

regularly ordered, repeating pattern extending in all three spatial dimensions.

Almost any object made of an elastic material could be used like a crystal, with

appropriate transducers, since all objects have natural resonant frequencies of

vibration. For example, steel is very elastic and has a high speed of sound. It was

often used in55 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


mechanical filters before quartz. The resonant frequency depends on size, shape,

elasticity, and the speed of sound in the material. High-frequency crystals are typically

cut in the shape of a simple, rectangular plate. Low-frequency crystals, such as those

used in digital watches, are typically cut in the shape of a tuning fork. For applications

not needing very precise timing, alow-cost ceramic resonator is often used in place of

a quartz crystal.

When a crystal of quartz is properly cut and mounted, it can be made to distort in an

electric field by applying a voltage to an electrode near or on the crystal. This property

is known as piezoelectricity. When the field is removed, the quartz will generate an

electric field as it returns to its previous shape, and this can generate a voltage. The

result is that a quartz crystal behaves like a circuit composed of an inductor, capacitor

and resistor, with a precise resonant frequency. (See RLC circuit.)

Fig 3.7.2 Schematic diagram of crystal oscillator

Quartz has the further advantage that its elastic constants and its size change in such a

way that the frequency dependence on temperature can be very low. The specific

characteristics will depend on the mode of vibration and the angle at which the quartz

is cut (relative to its crystallographic axes). Therefore, the resonant frequency of the

plate, which depends on its size, will not change much, either. This means that a

quartz clock, filter or oscillator will remain accurate. For critical applications the

quartz oscillator is56 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


mounted in a temperature-controlled container, called a crystal oven, and can also be

mounted on shock absorbers to prevent perturbation by external mechanical

vibrations.

Modeling:

Electrical model

Electronic symbol for a piezoelectric crystal resonator. A quartz crystal can be

modelled as an electrical network with a low impedance (series) and a

high impedance (parallel) resonance point spaced closely together. Mathematically

(using the Laplace transform) the impedance of this network can be written as:

or,

where s is the complex frequency ( ), is the series resonant frequency

in radians per second and is the parallel resonant frequency in radians per

second. Schematic symbol and equivalent circuit for a quartz crystal in an oscillator

Adding additional capacitance across a crystal will cause the parallel resonance to

shift downward. This can be used to adjust the frequency at which a crystal oscillates.

Crystal manufacturers normally cut and trim their crystals to have a specified

resonance frequency with a known 'load' capacitance added to the crystal. For

example, a crystal intended for a 6 pF load has its specified parallel resonance

frequency when a 6.0 pF capacitor is placed across it. Without this capacitance, the

resonance frequency is higher.

Resonance modes57 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


A quartz crystal provides both series and parallel resonance. The series resonance is a

few kilohertz lower than the parallel one. Crystals below 30 MHz are generally

operated between series and parallel resonance, which means that the crystal appears

as an inductive reactance in operation. Any additional circuit capacitance will thus

pull the frequency down. For a parallel resonance crystal to operate at its specified

frequency, the electronic circuit has to provide a total parallel capacitance as specified

by the crystal manufacturer.

Crystals above 30 MHz (up to >200 MHz) are generally operated at series resonance

where the impedance appears at its minimum and equal to the series resistance. For

these crystals the series resistance is specified (<100 Ω) instead of the parallel

capacitance. To reach higher frequencies, a crystal can be made to vibrate at one of

its overtone modes, which occur near multiples of the fundamental resonant

frequency. Only odd numbered overtones are used. Such a crystal is referred to as a

3rd, 5th, or even 7th overtone crystal. To accomplish this, the oscillator circuit usually

includes additional LC circuits to select the desired overtone.

Temperature effects

A crystal's frequency characteristic depends on the shape or 'cut' of the crystal. A

tuning fork crystal is usually cut such that its frequency over temperature is a

parabolic curve centered around 25 °C. This means that a tuning fork crystal oscillator

will resonate close to its target frequency at room temperature, but will slow down

when the temperature either increases or decreases from room temperature. A

common parabolic coefficient for a 32 kHz tuning fork crystal is −0.04 ppm/°C².

In a real application, this means that a clock built using a regular 32 kHz tuning fork

crystal will keep good time at room temperature, lose 2 minutes per year at 10 degrees

Celsius above (or below) room temperature and lose 8 minutes per year at 20 degrees

Celsius above (or below) room temperature due to the quartz crystal.58 DEPARTMENT OF ELECTRONICS MITS,


The frequency stability is determined by the crystal's Q . It is inversely dependent on

the frequency, and on the constant that is dependent on the particular cut. Other

factors influencing Q are the overtone used, the temperature, the level of driving of

the crystal, the quality of the surface finish, the mechanical stresses imposed on the

crystal by bonding and mounting, the geometry of the crystal and the attached

electrodes, the material purity and defects in the crystal, type and pressure of the gas

in the enclosure, interfering modes, and presence and absorbed dose of ionizing and

neutron radiation.

Temperature influences the operating frequency; various forms of compensation are

used, from analog compensation (TCXO) and microcontroller compensation (MCXO)

to stabilization of the temperature with a crystal oven (OCXO). The crystals possess

temperature hysteresis ; the frequency at a given temperature achieved by increasing

the temperature is not equal to the frequency on the same temperature achieved by

decreasing the temperature. The temperature sensitivity depends primarily on the cut;

the temperature compensated cuts are chosen as to minimize frequency/temperature

dependence. Special cuts can be made with a linear temperature characteristics; the

LC cut is used in quartz thermometers. Other influencing factors are the overtone

used, the mounting and electrodes, impurities in the crystal, mechanical strain, crystal

geometry, rate of temperature change, thermal history (due to hysteresis), ionizing

radiation, and drive level.

Crystals tend to suffer anomalies in their frequency/temperature and

resistance/temperature characteristics, known as activity dips. These are small

downward (in frequency) or upward (in resistance) excursions localized at certain

temperatures, with their temperature position dependent on the value of the load

capacitors.

Mechanical stresses also influence the frequency. The stresses can be induced by

mounting, bonding, and application of the electrodes, by differential thermal

expansion of the mounting, electrodes, and the crystal itself, by differential thermal

stresses when there is a temperature gradient present, by expansion or shrinkage of the

bonding materials during curing, by the air pressure that is transferred to the ambient

pressure within the crystal enclosure, by the stresses of the crystal lattice itself (non

uniform growth,59 DEPARTMENT OF ELECTRONICS MITS,


impurities, dislocations), by the surface imperfections and damage caused during

manufacture, and by the action of gravity on the mass of the crystal; the frequency can

therefore be influenced by position of the crystal. Other dynamic stress inducing

factors are shocks, vibrations, and acoustic noise. Some cuts are less sensitive to

stresses; the SC (Stress Compensated) cut is an example. Atmospheric pressure

changes can also introduce deformations to the housing, influencing the frequency by

changing stray capacitances.

Atmospheric humidity influences the thermal transfer properties of air, and can

change electrical properties of plastics by diffusion of water molecules into their

structure, altering the dielectric constants and electrical conductivity .

Other factors influencing the frequency are the power supply voltage, load impedance,

magnetic fields, electric fields (in case of cuts that are sensitive to them, e.g. SC), the

presence and absorbed dose of γ-particles and ionizing radiation, and the age of the

crystal.

Crystals undergo slow gradual change of frequency with time, known as aging. There

are many mechanisms involved. The mounting and contacts may undergo relief of the

built- in stresses. Molecules of contamination either from the residual

atmosphere, outgassed from the crystal, electrodes or packaging materials, or

introduced during sealing the housing can be adsorbed on the crystal surface,

changing its mass; this effect is exploited in quartz crystal microbalances . The

composition of the crystal can be gradually altered by outgassing, diffusion of atoms

of impurities or migrating from the electrodes, or the lattice can be damaged by

radiation. Slow chemical reactions may occur on or in the crystal, or on the inner

surfaces of the enclosure. Electrode material, e.g. chromium or aluminium, can react

with the crystal, creating layers of metal oxide and silicon; these interface layers can

undergo changes in time. The pressure in the enclosure can change due to varying

atmospheric pressure, temperature, leaks, or outgassing of the materials inside.

Factors outside of the crystal itself are e.g. aging of the oscillator circuitry (and e.g.

change of capacitances), and drift of parameters of the crystal oven. External

atmosphere composition can also influence the aging.60 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


3.8 IC L293D :

L293D is a dual H‐Bridge motor driver, so with one IC we can interface two DC motors which can be controlled in both clockwise and counter clockwise direction and if you have motor with fix direction of motion. You can make use of all the four I/Os to connect up to four DC motors.

L293D has output current of 600mA and peak output current of 1.2A per channel.

Moreover for protection of circuit from back EMF output diodes are included within

the IC. The output supply (VCC2) has a wide range from 4.5V to 36V, which has

made L293D a best choice for DC motor driver.

Pin configuration

Fig. 3.8.1 Pin configuration61 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Electrical Characteristic

Table 3.8.1 Electrical Characteristic

Supply voltage(Vss) is the Voltage at which we wish to drive the motor. Generally we

prefer 6V for dc motor and 6 to 12V for gear motor, depending upon the rating of the

motor.

Logical Supply Voltage will decide what value of input voltage should be considered as

high or low .So if we set Logical Supply Voltage equals to +5V, then -0.3V to 1.5V

will be considered as Input Low Voltage and 2.3 V to 5V will be considered as Input

High Voltage.

L293D has 2 Channels .One channel is used for one motor.

Channel 1 - Pin 1 to 8 ; Channel 2 - Pin 9 to 16

Enable Pin is use to enable or to make a channel active .Enable pin is also called as Chip

Inhibit Pin. All Input(Pin No. 2,7,10and 15) of L293D IC is the output from

microcontroller (ATmega8).

Eg-We connected (Pin No. 2, 7, 10 and 15) of L293D IC to (Pin No. 14,15,16and

17)of ATmega8 respectively in our robots, because on pin 14 and 15 of ATmega8 we

can generate PWM. All Output (Pin No. 3, 6,11and 14) of L293D IC goes to the input

of Right and Left motor through RMC(4 pin Connector).62 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Fig 3.8.2 Motor Driving Circuit

3.6.3 Motor Driving Table

Table 3.8.2S Motor Driving Table

Characteristics

OUTPUT 1 --- Negative Terminal of Right Motor

OUTPUT 2 --- Positive Terminal of Right Motor

OUTPUT 3 --- Positive Terminal of Left Motor

OUTPUT 4 --- Negative Terminal of Left Motor63 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


CHAPTER 4

4.1 Algorithm :

An algorithm is designed to rotate motors in different directions viz. forward,

backward, left turn, right turn and stop corresponding to the thrust applied on the

mobile keys assigned to them. The algorithm for the same is mentioned below .

1.Make port 1 as input port

2.Make port 2 as output port

3.Check if input at port 1 is F2 Hex then move robot in forward direction else go to step

4.Check if input at port 1 is F8 Hex then move robot in backward direction else go to step.

5.Check if input at port 1 is F6 Hex then robot takes right turn else go to step 6.

6.Check if input at port 1 is F4 Hex then robot takes left turn else go to step 7.

7.Go to step 3 and continuously check the input.

4.2 Software used:

Keil Software:

This tutorial will assist you in writing your first 8051 Assembly language program

using the popular Keil Compiler. Keil offers an evaluation package that will allow the

assembly and debugging of files 2K or less.

1.Open Keil from the Start menu

2.The Figure below shows the basic names of the windows referred in this document

2.Name the project ‘Toggle.a51’

3.Click on the Save Button.

4.The device window will be displayed.

5.Select the part you will be using to test with. For now we will use the Dallas

Semiconductor part DS89C420.

6.Double Click on the Dallas Semiconductor.64 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Fig.no.4.2.1

Expand the Source Group 1 in the Tree menu to ensure that the file was added to the

project.65 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Flash Magic

it is use for creating the HEX file to burn in burner hardware .

Fig.no.4.2.2

1.Click on Target 1 in Tree menu

2.Click on Project Menu and selectOptions for Target 1

3.Select Target Tab

4.Change Xtal (Mhz) from 50.0 to11.0592

5.Select Output Tab

6.Click on Create Hex File check box

7.Click OK Button

8.Click on Project Menu and select Rebuild all Target Files

9.In the Build Window it should report ‘0 Errors (s), 0 Warnings’

10.You are now ready to Program your part66 DEPARTMENT OF ELECTRONICS MITS,


Chapter 5

PCB DESIGNING:

5.1 :PCB (PRINTED CIRCUIT BOARD)

A printed circuit board, or PCB, is used to mechanically support and electrically

connectelectronic components using conductive pathways, tracks

or traces etched from copper sheetslaminated onto a non-conductive substrate. It is

also referred to as printed wiring board (PWB) or etched wiring board. A PCB

populated with electronic components is a printed circuit assembly (PCA), also known

as a printed circuit board assembly (PCBA).

PCBs are inexpensive, and can be highly reliable. They require much more layout

effort and higher initial cost than either wire-wrapped or point-to-

point constructed circuits, but are much cheaper and faster for high-

volume production. Much of the electronics industry's PCB design, assembly, and

quality control needs are set by standards that are published by the IPCorganization.

POWER SUPPLY

There is 5V supply voltage required for this project. An ac 9-0-9 V mains transformer

is connected via a mains lead. The transistor is voltage regulator IC. It regulates 4.8V

dc .

WorkingThe working is quite clear. It is describe in following steps.

Step down transformer convert 220V AC into 4.8V AC

It convert AC voltage into pulsating DC voltage

The filter stage uses a shunt capacitor to filter out ripples from pulsating DC

The regulator stage gives a regulated output of a fixed voltage.

The circuit runs on a power supply of 5V DC. A transformer 9-0-9V is used to step down the

ac mains voltage from 230V, to 9V AC. The combination of transformer & diode converts

this AC voltage into a pulsating DC voltage, which is filtered by using an electrolytic

capacitor of rating 1000µF, 25V. The IC BC547b provides a regulated power supply of 5V

DC. The 5V DC supply drives and the ICs in the circuit.67 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


5.2 PCB-DESIGNING

PCB Designing includes the following steps:-

PROCESSING

CLEANSING

PRINTING

ETCHING

DRILLING

SOLDERING

MASKING

Fig 5.1 PCB Designing process68 DEPARTMENT OF ELECTRONICS MITS,


PROCESSING

The layout of a PCB has to incorporate all the information on the board before one

can go on to the artwork preparation. This means that a concept that clearly defines all

the details of the circuit and partly also of the final equipment, is a prerequisite before

the actual layout can start. The detail circuit diagram is very important for the layout

designer and he must also be familiar with the design concept and with the philosophy

behind the equipment. The General Considerations are-

a-) Layout scale:- Depending on the accuracy required, artwork should be produced

at a 1:1 or 2:1 or even 4:1 scale. The layout is best prepared on the same scale as the

artwork. This prevents all the problems which might be caused by redrawing of layout

to the artwork scale.

b-) Grid system or Graph Paper: - It is commonly accepted practice to use these for

designing.

c-) Board types :-There are two side of a PCB board – Component side & Solder side.

Depending on these board are classified as-

Single-sided Boards : - These are used where costs have to be kept at a minimum & a

particular Circuit can be accommodated on such board. To jump over conductor

tracks, components have to be utilized. If this is not feasible,

jumper wires are used. (Jumper wires should be less otherwise double-sided PCB

should be considered.

Double-sided Boards : - These are made with or without plated through holes. Plated

through holes are fairly expensive.69 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


CLEANING

The cleaning of the copper surface prior to resist application is an essential step for

any type of PCB process using etches or plating resist.

After scrubbing with the abrasive, a water rinse will remove most of the remaining slurry.

Scrubbing

Water Rinse

Wet Brushing

Acid dip

Final Rinse

DryingPumice/ Acid Slurry

Tap Water

Tap Water

Hydrochloric Acid-HCl

De-ionized Water

Oven or Blowing of air.Fig5.2Cleaningprocess



ETCHING

It is of utmost importance to choose a suitable Etchant Systems. There are many

factors to be considered:-

Etching speed

Copper solving capacity

Etchant price

Pollution character

Operation characteristics of different etchants:-Factor Corrosive Neutralization Toxicity Required Operation

Etchant -ness disposition problem

ventilation cost

FeCl3 High Medium Low Low Medium

CuCl2 High Low Medium Medium Low

Chromic High High High High High

acid

Alkaline High Medium Medium High High

ammonia

Table 5.2.1 Characteristics of different etchants

We have uses FeCl3 (Conc. 120 g/litre 0.1 M) for etching.

Reactions Involved:-

FeCl3 +3H 2O Fe(OH)3 + 3HCl (Free acid attack to copper)

FeCl3 + Cu FeCl2 + CuCl

FeCl3 + CuCl FeCl2 + CuCl2

CuCl2 +Cu 2CuCl



DRILLING

The importance of hole drilling into PCB’s has further gone with electronic

component miniaturization and its need for smaller holes diameters (diameters less

than half the board thickness) and higher package density.

The following hole diameter tolerances have been generally accepted wherever no

other specifications are mentioned.Hole Diameter (D) <= 1mm + / - 0.05 mm

Hole Diameter (D) > 3 mm + / – 0.1 mm

Drill bits are made up of high-speed steel (HSS), Glass epoxy material, Tungsten Carbide.

SOLDERING

Flux should be removed after Soldering. It is done through washing by 0.5—1 % HCl

followed by Neutralization in dilute alkali to remove corrosive flux.Non-corrosive is

removed byIso-Propanal.

MASKING

It is done for the protection of conductor track from Oxidation.72 DEPARTMENT OF ELECTRONICS MITS,


5.3 Designing of PCB Layout

A PCB layout is required to place components on the PCB so that the component area

can be minimized and the components can be placed in an efficient manner. The

components can be placed in two ways, either manually or by software. The manual

procedure is quiet cumbersome and is very inefficient. The other method is by the use

of computer software. This method is advantageous as it saves time and valuable

copper area. There are various software’s available for this purpose like-

Express PCB

Pad2pad

Protel PCB

PCB design e.t.c.

Many of them are loaded with auto routing and auto placement facility. The software

that we have used here is EXPRESS PCB. This software has a good interface, easy

editing options and a wide range of components.

Express P.C.B.

Express PCB is a very easy to use Windows application for laying out printed circuit

boards. There are two parts to Express PCB, Express SCH for drawing schematics and

Express PCB for designing circuit boards. We downloaded the software from the

website

www.expresspcb.com .

There are lots of functions available in the software. This software is free of cost and

it is very easy to use. The different layers of the PCB can be viewed by just a click of

a button on the interface. And we easily get its print on paper which is utilized for

further processing. We can design single sided PCB as well as Double Sided PCB

with this Software.73 DEPARTMENT OF ELECTRONICS MITS,


CHAPTER NO.6

APPLICATION

Since a cell phone controlled robot has overcome the limitations of the range of a

normal RF controlled robots, it has endless applications. It can be used by any layman

due to its simplistic nature. Also any available cell phone can be used to control this

robot. These features extend the scope of this robot to a large number of diversified

fields.

Some of the common applications have been listed below:

It can be modified to control home appliances (like - door locks, A.C. etc) from

anywhere in the world just by dialling some numbers.

It can be used for security purposes where going near the target is highly risky(like - to

destroying land mine, to examine earth quake affected buildings etc)

It can be used for remote monitoring/data collection (like rain water data collection,

vending machine status, water level monitoring in flood prone rivers).

It can be used as spy bot to penetrate into the enemy’s defence system.

Such type invention a system for activating & deactivating a plurality of different

appliances located on telephone subscriber’s residential or business premises.

It is also used for home appliances controlled by mobile from any distance.

It is also used to control the car and stop it with the help of mobile from anywhere.74 DEPARTMENT OF ELECTRONICS MITS,


6.1 WEB –CAM:

Wireless security cameras are closed-circuit television (CCTV) cameras that transmit

a video and audio signal to a wireless receiver through a radio band. Many wireless

security cameras require at least one cable or wire for power; "wireless" refers to the

transmission of video/audio. However, some wireless security cameras are battery-

powered, making the cameras truly wireless from top to bottom.

Wireless cameras are proving very popular among modern security consumers due to

their low installation costs (there is no need to run expensive video extension cables)

and flexible mounting options; wireless cameras can be mounted/installed in locations

previously unavailable to standard wired cameras

The term 'webcam' may also be used in its original sense of a video camera connected

to theWeb continuously for an indefinite time, rather than for a particular session,

generally supplying a view for anyone who visits its web page over the Internet. Some

of them, for example, those used as online traffic cameras , are expensive,

rugged professional video cameras .

Videocalling and videoconferencing

As webcam capabilities have been added to instant messaging , text chat services such

as AOL Instant Messenger , and VoIP services such as Skype , one-to-one live video

communication over the Internet has now reached millions of mainstream PC users

worldwide. Improved video quality has helped webcams encroach on traditional video

conferencing systems. New features such as automatic lighting controls, real-

time enhancements (retouching, wrinkle smoothing and vertical stretch),

automatic face tracking and autofocus, assist users by providing substantialease-of-

use, further increasing the popularity of webcams.75 DEPARTMENT OF ELECTRONICS MITS,

LUCKNOW


Fig.no.6.1.176 DEPARTMENT OF ELECTRONICS MITS,


Video security

Webcams are also used as security cameras . Software is available to allow PC-

connectedcameras to watch for movement and sound,[9] recording both when they are

detected. These recordings can then be saved to the computer, e-mailed, or uploaded

to the Internet. In onewell-publicized case,a computer e-mailed images of the burglar

during the theft of the computer, enabling the owner to give police a clear picture of

the burglar's face even after the computer had been stolen.

Recently webcam privacy software has been introduced by such companies such as

Stop Being Watched. The software exposes access to a webcam and prompts the user

to allow or deny access by showing what program is trying to access the webcam.

Allowing the user to accept a trusted program the user recognizes or terminate the

attempt immediately. Other companies on the market manufacture and sell sliding

lens covers that allow users to retrofit the computer and close access to the camera

lens.

In December 2011 Russia announced that 290,000 Webcams would be installed in

90,000 polling stations to monitor the Russian presidential election, 2012 . [11]

Video clips and stills

Webcams can be used to take video clips and still pictures . Various software tools in

wide use can be employed for this, such as PicMaster (for use

with Windows operating systems), Photo Booth (Mac),

or Cheese (with Unix systems).

Input control devices

Special software can use the video stream from a webcam to assist or enhance a user's

control of applications and games. Video features, including faces, shapes, models

and colors can be observed and tracked to produce a corresponding form of control.

For example, the position of a single light source can be tracked and used to emulate a

mouse pointer, a head mounted light would enable hands-free computing and would

greatly improve computer accessibility . This can be applied to games, providing

additional control. Free Track is a free webcam motion tracking application

for Microsoft Windows77 DEPARTMENT OF ELECTRONICS MITS,


that can track a special head mounted model in up to six degrees of freedom and

output data to mouse, keyboard, joystick and Free Track supported games By

removing the IR filter of the webcam, IR LEDs can be used, which has the advantage

of being invisible to the naked eye, removing a distraction from the user. Track IR is a

commercial version of this technology.

The Eye Toy for the PlayStation 2 (The updated PlayStation 3 equivalent is

the PlayStation Eye) and similarly the Xbox Live Vision Camera and the Kinect AKA

'Project Natal' for theXbox 360 and Xbox Live are color digital cameras that have

been used as control input devices by some games.

Small webcam-based PC games are available as either standalone executables or

inside web browser windows using Adobe Flash .

Technology

Webcams typically include a lens (shown at top), an image sensor (shown at bottom),

and supporting circuitry. Webcams typically include a lens, an image sensor , support

electronics, and may also include a microphone for sound. Various lenses are

available, the most common inconsumer-grade webcams being a plastic lens that can

be screwed in and out to focus the camera. Fixed focus lenses, which have no

provision for adjustment, are also available. As a camera system's depth of field is

greater for small image formats and is greater for lenses with a large f-number (small

aperture), the systems used in webcams have a sufficiently large depth of field that the

use of a fixed focus lens does not impact image sharpness to a great extent.

Image sensors can be CMOS or CCD , the former being dominant for low-

cost cameras, but CCD cameras do not necessarily outperform CMOS-based cameras

in the low cost price range. Most consumer webcams are capable of

providing VGA resolution video at a frame rateof 30 frames per second. Many newer

devices can produce video in multi- megapixelresolutions, and a few can run at high

frame rates such as the PlayStation Eye , which can produce 320×240 video at 120

frames per second.78 DEPARTMENT OF ELECTRONICS MITS,


Support electronics read the image from the sensor and transmit it to the host

computer. The camera pictured to the right, for example, uses a Sonix SN9C101 to

transmit its image overUSB . Typically, each frame is transmitted uncompressed

in RGB or YUV or compressed asJPEG . Some cameras, such as mobile phone

cameras , use a CMOS sensor with supporting electronics "on die", i.e. the sensor and

the support electronics are built on a single silicon chipto save space and

manufacturing costs. Most webcams feature built-in microphones to makevideo

calling and videoconferencing more convenient.

The USB video device class (UVC) specification allows for interconnectivity of

webcams to computers without the need for proprietary device drivers.

Microsoft Windows XP SP2,Linux [12] and Mac OS X (since October 2005) have UVC

support built in and do not require extra device drivers, although they are often

installed to add additional features.

Privacy

Many users do not wish the continuous exposure for which webcams were originally

intended, but rather prefer privacy. Such privacy is lost when Trojan horse

programs allow malicious hackers to activate the webcam without the user's

knowledge, providing the hackers with a live video and audio feed.Cameras such

as Apple's older external Sight cameras include lens covers to thwart this. Some

webcams have built-in hardwired LED indicators that light up whenever the camera is

active. It is not clear whether these indicators can be circumvented when webcams are

surreptitiously activated without the user's knowledge or intent, via spyware.

In mid-January 2005, some search engine queries were published in an on-

line forum[13] which allow anyone to find thousands of Panasonic- and Axis high-

end web cameras, provided that they have a web-based interface for remote viewing.

Many such cameras are running on default configuration, which does not require

any password login or IP address verification, making them viewable by anyone.79 DEPARTMENT OF ELECTRONICS MITS,


Parameters & Features

300k/20.0 megapixels resolution (by software).

High resolution CMOS colour sensors.

Large window capture size.

Video mode -24 bit true colour.

Interface –USB port.

Manual focus.

Automatic colour compensation.

Automatic brightness adjustment.

Images focus -6cm to infinity.

Noise signal ratio: greater than 48db.

Dynamic range greater than 72db.

Software with fast snap function

Driver installations

Plug the webcam into the computer first. Insert the driver /application CD into CD-ROM

.wait for second you will find auto run page .Double click the button of auto run page

file and the system will automatically run necessary file. Click next -> click finish.

You may find AMCAP on the desktop, click AMCAP screen shall display the image

on the AMCAP window, if not select option on the top of the window after click

Preview, you will be able to capture the image on screen. Run Amcap.exe and you

will see the picture. you also may change effect setting.

System Requirement:

CD ROM driver.

IBM PC or Laptop with USB port.

32MB or higher memory.

Pentium 200 or higher CPU.80 DEPARTMENT OF ELECTRONICS MITS,

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6.2 LPG Gas Leakage Detector:

MQ-6 Semiconductor Sensor for LPG

Sensitive material of MQ-6 gas sensor is SnO2, which with lower conductivity in

clean air. When the target combustible gas exist, The sensor’s conductivity is more

higher along with the gas concentration rising. Please use simple electronic circuit,

Convert change of conductivity to correspond output signal of gas concentration.

MQ-6 gas sensor has high sensitivity to Propane, Butane and LPG, also response to

Natural gas. The sensor could be used to detect different combustible gas, especially

Methane, it is with low cost and suitable for different application.

Fig. 6.2.1 Gas sensor

Configuration

Fig.6.2.281 DEPARTMENT OF ELECTRONICS MITS,

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Character Configuration

*Good sensitivity to Combustible gas in wide range

*High sensitivity to Propane, Butane and LPG

*Long life and low cost

*Simple drive circuit

Application

*Domestic gas leakage detector

*Industrial Combustible gas detector

*Portable gas detector

Table 6.2.182 DEPARTMENT OF ELECTRONICS MITS,

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Sensitivity Characteristics

Fig.6.2.3 Structure and configuration

Structure and configuration of MQ-6 gas sensor is shown as Fig. 3, sensor composed

by micro AL2O3 ceramic tube, Tin Dioxide (SnO2) sensitive layer, measuring

electrode and heater are fixed into a crust made by plastic and stainless steel net. The

heater provides necessary work conditions for work of sensitive components. The

enveloped MQ-4 have 6 pin, 4 of them are used to fetch signals, and other 2 are used

for providing heating current.83 DEPARTMENT OF ELECTRONICS MITS,


Notification

1 Following conditions must be prohibited

1.1Exposed to organic silicon steam Organic silicon steam cause sensors invalid,

sensors must be avoid exposing to silicon bond, fixature, silicon latex, putty or plastic

contain silicon environment

1.2High Corrosive gas If the sensors exposed to high concentration corrosive gas

(such as H2Sz, SOX，Cl2，HCl etc), it will not only result in corrosion of sensors

structure, also it cause sincere sensitivity attenuation.

1.3Alkali, Alkali metals salt, halogen pollution The sensors performance will be

changed badly if sensors be sprayed polluted by alkali metals salt especially brine, or

be exposed to halogen such as fluorin.

1.4Touch water Sensitivity of the sensors will be reduced when spattered or dipped in water.

1.5Freezing Do avoid icing on sensor’surface, otherwise sensor would lose sensitivity.

1.6Applied voltage higher Applied voltage on sensor should not be higher than

stipulated value, otherwise it cause down-line or heater damaged, and bring on

sensors’ sensitivity

characteristic changed badly.

2 Following conditions must be avoided

2.1Water Condensation Indoor conditions, slight water condensation will effect

sensors performance lightly. However, if water condensation on sensors surface and

keep a certain period, sensor’ sensitivity will be decreased.

2.2Used in high gas concentration No matter the sensor is electrified or not, if long

time placed in high gas concentration, if will affect sensors characteristic.

2.3Long time storage The sensors resistance produce reversible drift if it’s stored for

long time without electrify, this drift is related with storage conditions. Sensors should

be stored in airproof without silicon gel bag with clean air. For the sensors with long

time storage but no electrify, they need long aging time for stbility before using.84 DEPARTMENT OF ELECTRONICS MITS,

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2.4Long time exposed to adverse environment No matter the sensors electrified or not,

if exposed to adverse environment for long time, such as high humidity, high

temperature, or high pollution etc, it will effect the sensors performance badly.

2.5Vibration Continual vibration will result in sensors down-lead response then

repture. In transportation or assembling line, pneumatic screwdriver/ultrasonic

welding machine can lead this vibration.

2.6Concussion If sensors meet strong concussion, it may lead its lead wire disconnected.

2.7Usage For sensor, handmade welding is optimal way. If use wave crest welding

should meet the following conditions:

2.7.1Soldering flux: Rosin soldering flux contains least chlorine

2.7.2Speed: 1-2 Meter/ Minute

2.7.3Warm-up temperature：100±20℃2.7.4Welding temperature：250±10℃2.7.51 time pass wave crest welding machine

If disobey the above using terms, sensors sensitivity will be reduced.

IT DOESN’T WORK – WHAT I DO ?

1. Check that all components are in their correct place and the correct way around.

2.Check for unsoldered joints and solder bridges or splashes.

3.Is the 5V supply OK?

4.Any IC legs bent up under the IC body?85 DEPARTMENT OF ELECTRONICS MITS,

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LM 358P IC:

DESCRIPTION

These circuits consist of two independent, high gain, internally frequency

compensated which were designed specifically to operate from a single power supply

over a wide range of voltages. The low power supply drain is independent of the

magnitude of the power supply voltage. Application areas include transducer

amplifiers, dc gain blocks and all the conventional op-ampcircuits which now can be

more easily implemented in single power supply systems. For example, these circuits

can be directly supplied with the standard +5V which is used in logic systems and will

easily provide the required interface electronics without requiring any additional

power supply. In the linear mode the input common-mode voltage range includes

ground and the output voltage can also swing to ground, even though operated from

only a single power supply voltage.

Pin diagram86 DEPARTMENT OF ELECTRONICS MITS,


Future scope

This project demonstrates the tele/remote control of the electronic appliances and the

DC motors using mobile phone. However, a closed loop system that gives feedback to

the transmitter can be implemented so that output work done can be acknowledged by

the transmitter side. DTMF receiver and transmitter IC can be used to give feedback

to the controlling mobile. IR sensors can be used to automatically detect & avoid

obstacles if the robot goes beyond line of sight. This avoids damage to the vehicle if

we are maneuvering it from a distant place. Similarly, the current project can

interfaced with a camera (e.g. a Webcam) robot can be driven beyond line-of-sight &

range becomes practically unlimited as GSM networks have a very large range. GSM

Modules can be incorporated in our system to discover the status and location of the

robot.

This Project along with Tone generator and keypad can also be used to make our own

private telephone exchange.87 DEPARTMENT OF ELECTRONICS MITS,

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APPENDIX A:

A complete program for this projectmov A,#0FFH //to move OFF in accumulator

mov p1,A //to make port1 as input

mov B,#00H //to move 00 in register B

mov p2,B //move content of B to make it as o/p

forward: mov A,p1 //to move port1 data in accumulator

Cjne A,#0F2H,left //to move forward

setb p2.0 //to make p2.0 high

Setb p2.2 //to make p2.0 high

clr p2.1 //to make p2.1 low


sjmp forward //to make control in this loop

left :cjne A,#0F4H,stop //to move left





sjmp forward //to jump control to forward level

stop :cjne A,#0F5H,right //to move right88 DEPARTMENT OF ELECTRONICS MITS,







back :cjne A,#0F8H,back //to move right






right :cjne A,#0F6H,forward //check again






here:sjmp here //to make control here

End //to end the program89 DEPARTMENT OF ELECTRONICS MITS,


Conclusion

It can be concluded that mobile controlled robots can be constructed using the

components: IC CM8870 (DTMF decoder), (AT89S5) microcontroller and L293D

(motor drivers). Locomotion of the robot in different directions can be controlled and

maneuvered by pressing the assigned keys on the mobile phone (in this experiment;

key

‘5’ for forward motion, key ‘7’ for left turn, key ‘8’ for stop, key ‘9’ for right turn and

key ‘0’ for backward motion). Similarly, household electric appliances can be

remotely controlled with the assistance of L293D and relay circuit.

Finally it is an object of this invention to provide a means for wireless control system

operate through mobile. Accordingly the present invention provides a system for

controlling appliances at any place, which is connect to a telephone switched network

using DTMF telephone signal.90 DEPARTMENT OF ELECTRONICS MITS,

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Bibliography:

“The 8051 Microcontroller and Embedded Systems” 2nd edition by Muhammad A.

Mazidi, Janice G. Mazidi, Rollin D. McKinley ,

An imprint of Pearson Education (2007)

“Electronics and Device Circuits” by Robert L. Boylstead and Louis Nashelsky


“Electronic Communication” by Dennis Ruddy and John Goolen


Digital system design –Moris mano

www.google.com

www.bricsworld.com

www.alldatasheet.com91 DEPARTMENT OF ELECTRONICS MITS,

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Dtmf Based Wireless Mobile Robot