smart zone sensing system with automatic control

Contents

1. Introduction`

2. Block Diagram & its Description

3. Circuit Diagram & its Description

4. Construction Guidelines

5. Applications & Future Developments

NOTE: Due to continuous improvement and development in the project design, project reports provided are accurate by 90%. The difference of 10% [if any] will be informed during project theory classes.

SMART ZONE SENSING SYSTEM WITH AUTOMATIC CONTROL

Smart Zone Sensing System With Automatic Control

1. INTRODUCTION

The project presented here is a novel approach towards vehicle navigation & safety implementation.

As the title suggests, the project is aimed at automatically sensing the areas / zones like “School

Zone”, “Hospital zone” or “Accident Zone”.

In convention, these special zones or areas are indicated at the roadside on a pillar or road sign

poles.

As an example, near school zone, the sign board displays “School Zone Ahead, Drive Slowly”, or

near a hospital, “Hospital Area-Do not Blow Horn”, but in reality rarely this is practices. Drivers go at

very high speed as usual near school zone, or operate the harsh horns loudly causing inconvenience

to the patients in the hospital.

Even though these are meant for the safety of the vehicles traveling and also for the general public, it

is hardly practices by the vehicle drivers. As a result, making the whole concept of displaying warning

sign and messages on the roadside boards meaningless.

To provide a better alternative, one can develop a system which will automatically sense such traffic

signs automatically and accordingly inform the drives and also assist him in controlling the vehicle

voluntarily or forcibly. All in all resulting in a very effective and fail proof system to provide traffic

regulation, safety and convenience of the people.

As the whole project not just limited for these few functions, this project can be made mandatory.

That way one can provide a more reliable security device and streamline traffic flow. Few additional

features which can be integrated with this system are, “Down Hill Detection”, “Auto-Breaking with

Obstacle detection” “auto Speed limit Sensor” etc.

As the design of this system goes, the project proposed here consists of a set of units

1) Zone / Area Unit

2) Vehicle Unit

The following block diagram shows the simplified arrangement of the system,

MAIN FEATURES OF THE PROJECT:

1. Effective in implementation.

2. Low power consumption, and compact size,

3. High reliability, due to the usage of power semiconductor devices,

6. Greater control range due the usage of Frequency Modulation with a PC.

7. Vehicles monitored from a remote area (no need of 'line-of-sight’ arrangement).

2. BLOCK DIAGRAM & ITS DESCRIPTION

In BRIEF: This ‘Smart Zone Sensing System with Automatic Control’ system works like this.

Each monitoring zones are fitted with RF Transmitter units with unique Identity Code. All the

vehicles must be fitted with RF Receiver and respective circuitry on their vehicle’s number

plate. Display will be fitted on the dash board for visual representation of the alert messages

sent by respective zone Transmitters.

When vehicle with 70 Kmph speed enters the school zone, it receives the alert

message”School Zone, Please go slowly. Speed limit it 30 KiloMeterPerHour”. Also receiver

checks the speed limit of the vehicle and found above 30 kmph then reduces it until crosses

the School Zone area.

When the same vehicle enters the Hospital Zone, it receives the alert message “Hospital

Zone, Please do not blow Horn”, and reduces the supply voltage to minimum level such that

horn should blow in low pitch.

The complete block diagram is shown in fig 2.2 and a transmitter position is shown in fig 2.1.

The explanation of each block goes like this:

RF TRANSMITTER: The Radio Frequency Transmitter transmits the zone code to the receiving units.

There are two zones in the present system: School Zone and Hospital Zone. Each Transmitter has

carrying frequency of 144 MHz and data frequency range between 17, 19, 22 and 25. Transmitter #1

is set to data frequency of 17 and Transmitter #2 is for 19.

HOSPITAL ZONE

TRANSMITTER #2

SCHOOL ZONETRANSMITTER

#1

FIG 2.1 DIAGRAM DEPICITING TRANSMITTER POSITIONS

RF RECEIVER: The Radio Frequency Receiver receives the Zone Code transmitted by the

Transmitter. According to the number of transmitter, here for Transmitter #1 & #2 respective output

pins go high. The output is fed to directed opto-coupler for further processing.

OPTO-COUPLER: The Opto-coupler, as name implies, couples the two stages i.e., RF receiver and

Buffer & Driver Unit optically. This stage provides the isolation between the receiving stage to driving

stage.

BUFFER & DRIVER UNIT: This unit provides unit gain amplification to the received Zone Code signal

and drives the relay for further feeding. The output of Zone Code signal is fed to Microcontroller chip

as input and gets Speed Limit & Low Horn commands from it and drives the two more blocks.

MICROCONTROLLER CHIP: This is heart of this system. This takes Zone Code signal as input and

generates four command signals for output purpose. The inherited software manipulates the inputted

data and generates four command signals. Depends upon the Zone Code, it generates set of two

RF TRANSMITTER #1

D1 D2 D3 D4

RF TRANSMITTER #2

D1 D2 D3 D4

RF RECEIVER

OPTO-COUPLEROPTO-COUPLEROPTO-COUPLEROPTO-COUPLER

BUFFER &

DRIVER UNIT

MICROCONTROLLER CHIP

LCD DISPLAY

VARIABLE POWER SOURCE

REDUCED POWER SOURCE

M

TO HORNTO VEHICLE’S

MOTOR

FIG 2.2 BLOCK DIAGRAM OF SMART ZONE SENSING SYSTEM

POWER SUPPLY

UNIT

command signals. If Zone Code is from School Zone Transmitter then the display message is

generated and Speed Limit Command is outputted. Suppose Zone Code is from Hospital Zone

Transmitter then respective display message is generated and Low Horn Command is outputted.

LCD DISPLAY: The Liquid Crystal Display shows the display messages generated by the

Microcontroller chip, which is depending upon the Zone Code received.

VARIABLE POWER SOURCE: When Speed Limit Command is generated after certain delay by the

Microcontroller chip, it is sent to this stage for reducing the speed. This stage actually lowers the

supply voltage to the vehicle’s motor.

REDUCED POWER SOURCE: When Low Horn Command is generated after certain delay by the

Microcontroller chip, it is sent to this stage for lowered horn sound. This stage actually lowers the

supply voltage to the speaker, such that horn sound will be minimized.

POWER SUPPLY UNIT: As this stage has driver & relay stages, requires dual regulated

power supply for working purpose. Specially designed +12 & +5 Volts regulated power

supply is used to give proper working voltage to the whole section.

3. Circuit Diagram & its Description

Based on the circuit diagrams this Smart Zone Sensing System With Automatic Control system has

following circuits: RF Transmitter, RF Receiver, Opto-coupler, Buffer & Driver Unit, Mother Board

89C51, LCD Interfacing, Variable Power Source, Reduced Power Source and finally Power Supply

Unit.

Before explaining the circuit description, let us see the basics of the Radio Frequency Techniques

and its communication details.

RADIO FREQUENCY CIRCUIT TECHNIQUES

Radio must surely be one of the

most fascinating aspects of

electronics. This part of explanation

provides a brief introduction to radio

communication before describing the

circuitry of RF / IR receivers and

transmitters. The aim has been to

provide the user with sufficient

information to what his or her

appetite for a subject which has a

broad appeal to a large number of

dedicated enthusiasts all over the

world.

Radio Frequency Signals:

Radio frequency signals are

generally understood to occupy a

frequency range, which extends from

a few tens of kilohertz to several

hundred giga-hertz. The lowest part

of radio frequency range, which is of practical use (below 30 kHz), is only suitable for narrow-band

communications. At this frequency, signals propagate as ground waves (following the curvature of

the earth) over very long distance. At the other extreme, the highest frequency range, which is of

FM broadcasting

TV bands 1V/V

3 M

Hz

100 m

Very high frequency, VHF

SW broadcasting

MW broadcastingMedium frequency, MF

300 KHz 1 Km

LW broadcastingLow frequency, LF

10 Km

30 KHz

Fig ( A) The Radio Frequency Spectrum

3 GHz 10 cm

Frequency Wavelength

30 MHz 10 m

30 MHz 1 m

Ultra high frequency, UHF

High frequency, HF

practical importance, extends above 30GHz. At these ‘microwave’ frequencies, considerable

bandwidths are available (sufficient to transmit many television channel using point-to-point links or to

permit very high definition radar systems) and signals tend to propagate strictly along ‘line-of-sight’

paths.

At other frequencies, signals may propagate by various means, including reflection from ionized

layers in the ionosphere. At frequencies between 3MHz and 30MHz, for example, ionospheric

propagation regularly permits intercontinental broadcasting and communications using simple

equipment within the scope of the enthusiastic radio amateur and short-wave listener.

For convenience, the radio frequency spectrum is divided into a number of bands, each spanning a

decade of frequency. The use to which each frequency range is put depends upon a number of

factors, paramount amongst which is the propagation characteristic within the band concerned. Other

factors, which need to be taken into account, include the efficiency of practical aerial system in the

range concerned and the bandwidth available. It is also worth noting that, although it may appear

from Figure A that a great deal of the radio frequency spectrum is not used, it should be stressed that

competition for frequency space is fierce. Frequency allocations are, therefore, ratified by

international agreement and the various user services carefully safeguard their own areas of the

spectrum.

Frequency and wavelength

Radio waves propagate in air (or space) at the speed of light (300 million meters per second). The

velocity of propagation[v], wavelength[] and frequency [f] of a radio wave are related by the

equation:

V = f = 3 X 108 m/s

This equation can be arranged to make f or the subject, as follows:

F = 3 X 108/ Hz and = 3 X 108 / fm

As an example, a signal at a frequency of 1 MHz will have a wavelength of 300 m whereas a signal at

a frequency of 10 MHz will have a wavelength of 30m.

Modulation

In order to convey information using a radio frequency carrier, the signal information must be

superimposed or ‘modulated’ onto the carrier. Modulation is the name given to the process of

changing a particular property of the carrier wave in sympathy with the instantaneous voltage (or

current) signal.

The most commonly used methods of modulation are amplitude modulation (AM) and frequency

modulation (FM). In the former case, the carrier amplitude (its peak voltage) varies according to the

voltage, at any instant, of the modulating signal. In the latter case, the carrier frequency is varied in

accordance with the voltage, at any instant, of the modulating signal.

Figure B shows the effect of amplitude and frequency modulating a sinusoidal carrier (note that the

modulating signal is, in the case, also sinusoidal). In practice, many more cycles of the radio

frequency carrier would occur in the time span of the cycle of the modulating signal.

The term ‘angle modulation’ is the generic term encompassing both frequency modulation and phase

modulation. Frequency modulation involves operating directly upon the frequency determining

elements of an oscillator stage (e.g. by means of a variable capacitance diode placed across the

oscillator-tuned circuit or connected in series with a quartz crystal).

Phase modulation, on the other hand, acts indirectly by changing the phase of the signal in a

subsequent stage (e.g. by means of a variable

capacitance diode acting in a phase shifting circuit).

If the modulating signal (audio) is correctly tailored prior to

its application to the phase modulated stage, the end

result is identical to that of frequency modulation. The

reason for this is that, in a true FM system, the deviation

produced is the same for all modulating signals of equal

amplitude (i.e. the amount frequency deviation is

independent of the frequency of the modulating signal). In

a phase-modulated system, on other hand, the amount of

frequency deviation is proportional to both modulating

signal amplitude and modulating signal frequency. Thus in

Amplitude & Frequency Modulation

a phase modulated system without audio tailoring, a modulation signal of 2 kHz will produce twice as

much frequency deviation as an equal amplitude modulating signal of 1 kHz. The desired audio

response required to produce FM, therefore, is one, which rolls off the frequency response by half for

each doubling of frequency (equivalent to 6-dB per octave roll-off). This can be easily achieved using

a simple R-C low-pass filter.

Demodulation

Demodulation is the reverse of modulation and is the means by which the signal information is

recovered from the modulated carrier. Demodulation is achieved by means of a demodulator consists

of a reconstructed version of the original signal information present at the input of the modulator

stage within the transmitter.

Figure C shows the simplified block schematic of a simple radio communication system comprising

on AM transmitter and a ‘tuned radio frequency’ (TRF) receiver. Within the transmitter, the carrier

wave (of constant frequency) is generated by means of a radio frequency oscillator stage. In order to

ensure that the carrier is both accurate and within in frequency, this stage would normally employ a

quartz crystal within its frequency generating circuitry.

The output of the modulator (a modulated carrier) is amplified before outputting to the aerial system.

The output is usually carefully filtered to remove any spurious signals (harmonics) which may be

present and which may otherwise cause interference to other services.

At the receiver, the signal produced by the receiving aerial is a weak copy of the transmitted signal

(its level is usually measured in a V). Also present will be countless other signals at different

frequencies (and some with appreciably larger amplitude than the desired signal). These unwanted

signals must be rejected by the receiver’s radio frequency tuned circuits if they are no to cause

problems in later stages.

AFAMPLIFIER

RFOSCILLATOR

MODULATORRF

AMPLIFIER

Mic.

DEMODULATORRFAMPLIFIER

AFAMPLIFIER

LS

Fig ( C ) Typical Radio Transmitter & Receiver

RF transmitter

This part transmits unique Zone Code signal towards the RF Receiver part. There are two

transmitters Transmitter #1 for School Zone and Transmitter #2 for Hospital Zone. Both are identical

except the input pin, hence only one circuit is shown for clarity purpose.

INTRODUCTION

ASIC: Application Specific Intergrated Circuit [ASIC] is another option for embedded hardware

developers. The ASIC needs to be custom-built for a specific application, so it is costly. If the

embedded system being designed is a consumer item and is likely to be sold in large quantities, then

going the ASIC route is the best option, as it considerably reduces the cost of each unit. In addition,

size and power consumption will also be reduced. As the chip count (the number of chips on the

system) decreases, reliability increases.

If the embedded system is for the mass market, such as those used in CD players, toys, and mobile

devices, cost is a major consideration. Choosing the right processor, memory devices, and

peripherals to meet the functionality and performance requirements while keeping the cost

reasonable is of critical importance. In such cases, the designers will develop an Application Specific

Integrated Circuit or an Application Specific Microprocessor to reduce the hardware components and

hence the cost. Typically, a developer first creates a prototype by writing the software for a general-

purpose processor, and subsequently develops an ASIC to reduce the cost.

Oscillator: An electronic device that generates sinusoidal oscillations of desired frequency is known

as a sinusoidal oscillator. Although we speak of an oscillator as “generating” a frequency, it should be

noted that it does not create energy, but merely acts as an energy converter. It receives d.c. energy

and changes it into a.c energy of desired frequency. The frequency of oscillations depends upon the

constants of the device.

A circuit which produces electrical oscillations of any desired frequency is known as an oscillatory

circuit or tank circuit. A simple oscillatory circuit consists of a capacitor (C) and inductance coil (L) in

parallel. This electrical system can produce electrical oscillations of frequency determined by the

values of L and C. The sequence of charge and discharge results in alternating motion of electrons or

an osciallating current. The energy is alternately stored in the electric field of the capacitor and the

magnetic field of the inductance coil. This intercharge of energy between L and C is repeated over

and again resulting in the production of oscillations.

In order to obtain continuous undamped a.c. output from the tank circuit, it is necessary to supply the

correct amount of power to the circuit. The most practical way to do this is to supply d.c. power to

some device which should convert it to necessary a.c. power for supply to the tank circuit. This can

be achieved by employing a transistor circuit. Because of its ability to amplify, a transistor is very

efficient energy converter i.e. it converts d.c. power to a.c. power. If the damped oscillations in the

tank circuit are applied to the base of transistor, it will result in an amplified reproduction of

oscillations in the collector circuit. Because of this amplification more energy is available in the

collector circuit than in the base circuit. If a part of this collector-circuit energy is feedback by some

means to the base circuit in proper phase to aid the oscillations in the tank circuit, then its losses will

be overcome and continuous undamped oscillations will occur.

Hartley Oscillator is very popular and is commonly used as a local oscillator in radio receivers. It has

two main advantages viz., adaptability to a wide range of frequencies and is easy to tune.

RF TRANSMITTER

The RF transmitter is built around the ASIC and common passive and active components, which are

very easy to obtain from the material shelf. The circuit works on Very High Frequency band with wide

covering range. The Carrier frequency is 144 MHz and Data frequencies are 17 MHz,19 MHz,22 MHz

& 25 MHz. It should be noted that ASIC or Application Specific Integrated Circuit is proprietary

product and data sheet or pin details or working principles are not readily available to the user.

PARTS LIST

CIRCUIT DESCRIPTION :

The ASIC Transmitter IC has four inputs and only one output pin. The four inputs are for the

frequency range of 17 KHz, 19 KHz, 22 KHz and 25 KHz and four switches are provided for each

range. When any one switch is selected, that frequency is added to the Transmitter circuit as data

frequency and transmitted in the air. The Crystal X1 with two coupling capacitor provides the working

oscillator frequency to the circuit. The Capacitors C6 and C7 are to stabilize the crystal oscillator

frequency.

The ASIC output is added to the transmitter circuit’s oscillator transistor T1s base. The data

frequency is added with carrier frequency 147 MHz and aired for transmitting purpose. The transistor

T1 is heart of the Hartely Oscillator and oscillates at carrier frequency of 147 MHz along with tuned

circuit formed by coil L1 and capacitor C4. The Data frequency is fed to T1 on base through resistors

R4 and R5. Capacitors C1 and C3 and for stabilizing the tuned circuit along with resistor R3.

To increase the range of the circuit, transmitting signals must be strong enough to travel the long

distance [i.e., upto 100 meters in this prototype]. So the generated signals are made strong by

amplifying to certain level with the help of Transistor T2 and associated circuit.

SEMICONDUCTORS:

IC ASIC 1T1 BC 547 NPN Transistor 1T2 BF 494 NPN Transistor 1RESISTORS:

R1 & R2 2.7 K Ohm ¼ Watt 2

R3 & R6 330 K Ohm ¼ Watt 2

R4 1 K Ohm ¼ Watt 1


CAPACITORS:

C1, C2 0.001 Pico Farad Capacitor 2C3 & C7 0.022 Pico Farad Capacitor 2C4 4.7 Pico Farad Capacitor 1C5 & C6 0.01 Micro Farad Capacitor 2MISCELLANEOUS:

X1 1.44 MHz Crystal 1

S1 to S4 ON/OFF SWITCHES 4

L1 RF Coil 200mH 1

L2 Aerial or Telescopic Antenna 1

The Radio frequency thus generated is fed to pre-amplifier transistor T2 on base terminal. The

resistor R6 provides the bias voltage to T2 and capacitors C5 & C7 removes the noise and harmonics

present in the circuit. The antenna coil L2 transmits the radio frequency in the air.

CIRCUIT DIAGRAM OF RF TRANSMITTER

R6

R4 C1 R5

C5

R3 330K

R2 2K7

C7

C2 0.001

T1

C3 C4

L1

L2

T2

R1

+Vcc

Gnd

17 KHz S1

19KHz S2

22 KHz S3

25 KHz S4ASIC IC

C6

C7X1

RF RECEIVER

This circuit is built around the ASIC i.e., Application Specific Integrated Circuit, hence less circuitry is

observed. The Radio Frequency tuned circuit has 144 M Hz carrier frequency with four options viz.,

17Khz,19Khz,22KHz and 25KHz.

The transmitted signals are received on coil L1 which acts as receiver antenna. The oscillator

transistor removes the received signals from 147MHz carrier frequency and fed to ASIC IC. The tank

circuit formed by C1 and L1 gives the carrier frequency range. The current limiting resistor R1 and

bypass capacitor C5 stabilizes the oscillator. The resistor R2,R3 and R4 provide the biasing voltage

to the oscillator transistor T1. Capacitors C2 and C3 are there to bypass the noise and harmonics

present in the received signals. Through coupling capacitor C7 output of the RF Receiver is fed to

ASIC IC.

The ASIC IC manipulates the received signal and gives out four channels as output viz.,

17KHz,19KHz,22KHz and 25KHz. Each channel is amplified by pre-amplifier transistor T2 along with

bias resistor R9. The output of the pre-amplifier transistor is fed to relay driver stage to activate the

respective relay ON. The Darlington pair T3 and T4 are arranged in driver stage to drive the low

impedance relay.

PARTS LIST

Source: Magnum Technologies.

SEMICONDUCTORS:

IC ASIC 1T1 BC 547 NPN Transistor 1T2 BF 494 NPN Transistor 4T3&T4 BC 548 NPN Transistor 8RESISTORS:

R1 & R2 270 K Ohm ¼ Watt 2

R3 & R6 220 Ohm ¼ Watt 2

R4 2.2 K Ohm ¼ Watt 1

R5 2.2 M Ohm ¼ Watt 1


R8 100 Ohm ¼ Watt 4


CAPACITORS:

C1, C2 0.001 Pico Farad Capacitor 2C3 & C7 0.022 Pico Farad Capacitor 2C4 4.7 Pico Farad Capacitor 1C5 & C6 0.01 Micro Farad Capacitor 2L1 RF Coil 200mH 118

CIRCUIT DIAGRAM OF RF RECEIVER

Source: Magnum Technologies.19

C5

C3

L1

C2

C1

R1

R2

C4

T1

+Vcc

141312111098

1234567

ASIC IC

T3

R8

RL1

T42

T3

R8

RL2

T42

+Vcc

T2

T2

C6

C7R3

R4 R5

R6

R7R9

R9

OPTO-COUPLER

Introduction:

OPTO-COUPLER IC MCT 2E: Buffers does not affect the logical state of a digital signal

( i .e. logic 1 input results into logic 1 output where as logic 0 input results into logic 0

output). Buffers are normally used to provide extra current drive at the output are

used in interfacing applications. This 6-pin DIL packaged IC MCT 2E acts as Buffer as-well-as

Isolator. The input signals may be of 2.5 to 5V digital TTL compatible or DC analogue the IC gives 5V

constant signal output. The IC acts as isolator and provides isolation to the main circuit from varying

input signals. The working voltage of IC is fed at pin-5 and input to pin-1. The pin-2 is ground and pin-

4 is output. Note that pin-3 and pin-4 are not available pins, which must be left free. And the isolated

circuit must have its own ground connection.

The Opto-coupler IC has a photo diode which illuminates whenever input signal appears at pin-1. A

photo transistor, whose Base-lead open, receives the signal from the blinking photo diode and

passes it intact to the output pin-4. As this switching action is very fast, in term of micro seconds, the

signal transfer is successfully done without any delay and signal loss. As there is any physical

contact between photo diode and photo transistor is observed, it is used for isolating two sections of

the circuit. Especially the delicate digital circuits or signal sensitive stages whose output is supposed

to drive a fluctuating stage or mains operated load.

Since the digital outputs of the some circuits cannot sink much current, they are not capable of

driving relays directly. So, high-voltage high-current Darlington arrays are added to this opto-coupler

IC for interfacing low-level logic circuitry and peripheral power loads. Typical loads include relays,

solenoids, stepping motors, magnetic print hammers, multiplexed LED and incandescent displays,

and heaters.


Input Signal

Vcc

Gnd

CIRCUIT DIAGRAM OF OPTO-COUPLER

Parts List:

SEMICONDUCTORS

IC1 MCT 2E OPTO-ISOLATOR IC 1

RESISTORS

R0 & R1 33 K Ohm, ¼ Watt Carbon Type 1

R2 100 Ohm, ¼ Watt Carbon Type 1

R3 1 K Ohm, ¼ Watt Carbon Type 1

MISCELLANEOUS

D1 Red Indicator LED 1

TR1 & TR2 BC547 NPN Silicon Transistors 2

RL1 12 V, 700 Ohm DPDT Relay 1

Circuit Description:

This module is used where the main circuit is supposed to isolate itself from the mains operated

loads. The control signal is applied at input pin-1 and at pin-4 output is observed. Thus the signal

supplying circuit is isolated from this load driver circuit. But this signal level is not strong enough to

drive the low impedance relay. So, Darlington driver is created using two NPN transistors and boost

the signal level. The output signal from the Darlington driver stage is strong enough to actuate relay

RL1. This relay can be used to switch ON/OFF any mains operated load. The red LED D1 indicates

the relay position, whether load is ON or OFF. The resistors R1, R2, R3 and R4 are current limiting

resistors.


TR1 R2

451

RL1R3

R1

D1LED

TR2

R0

IC1

21

NOTE: If the load is inductive add a diode across the relay to prevent the back e.m.f produced by

quick switching action.


BUFFER & DRIVER STAGE

Let us see the general components of this Buffer & Driver stage.

HEX BUFFER / CONVERTER [NON-INVERTER] IC 4050:

Buffers does not affect the logical state of a digital signal (i.e.

logic 1 input results into logic 1 output where as logic 0 input

results into logic 0 output). Buffers are normally used to provide

extra current drive at the output, but can also be used to

regularise the logic present at an interface. And Inverters are

used to complement the logical state (i.e. logic 1 input results

into logic 0 output and vice versa). Also Inverters are used to

provide extra current drive and, like buffers, are used in

interfacing applications. This 16-pin DIL packaged IC 4050 acts

as Buffer as-well-as a Converter. The input signals may be of

2.5 to 5V digital TTL compatible or DC analogue the IC gives 5V

constant signal output. The IC acts as buffer and provides

isolation to the main circuit from varying input signals. The

working voltage of IC is 4 to 16 Volts and

propagation delay is 30 nanoseconds. It consumes

0.01 mill Watt power with noise immunity of 3.7 V

and toggle speed of 3 Megahertz.

RELAY: The traditional method of switching current

through a load, which requires isolation from the

controlling circuit, involves the use of an

electromechanical relay. Such devices offer a

simple, low-cost solution to the problem of

maintaining adequate isolation between the

controlling circuit and the potentially lethal voltages

associated with an a.c. main supply. The coils, which

provide the necessary magnetic flux to operate a

relay, are available for operation on a variety of

voltages between 5V and 115V d.c. and 12V to 250V

a.c. at currents of between 5 mA and 100 mA.


1

2

6

3

16

5

15

4

14

10

11

12

13

7

Vcc

Vss 8 9

IC 4050

Vcc

1 16

2

3

4

5

6

7

8

11

12

14

15

13

10

9

IC ULN 2004

23

ULN 2004: Since the digital outputs of the some circuits cannot sink much current, they are not

capable of driving relays directly. So, high-voltage high-current Darlington arrays are designed for

interfacing low-level logic circuitry and multiple peripheral power loads. The series ULN2000A/L ICs

drive seven relays with continuous load current ratings to 600mA for each input. At an appropriate

duty cycle depending on ambient temperature and number of drivers turned ON simultaneously,

typical power loads totalling over 260W [400mA x 7, 95V] can be controlled. Typical loads include

relays, solenoids, stepping motors, magnetic print hammers, multiplexed LED and incandescent

displays, and heaters. These Darlington arrays are furnished in 16-pin dual in-line plastic packages

(suffix A) and 16-lead surface-mountable SOICs (suffix L). All devices are pinned with outputs

opposite inputs to facilitate ease of circuit board layout.

The input of ULN 2004 is TTL-compatible open-collector outputs. As each of these outputs can sink a

maximum collector current of 500 mA, miniature PCB relays can be easily driven using ULN 2004.

No additional free-wheeling clamp diode is required to be connected across the relay since each of

the outputs has inbuilt free-wheeling diodes. The Series ULN20x4A/L features series input resistors

for operation directly from 6 to 15V CMOS or PMOS logic outputs.

1N4148 signal diode: Signal diodes are used to process information (electrical signals) in circuits, so

they are only required to pass small currents of up to 100mA. General purpose signal diodes such as

the 1N4148 are made from silicon and have a forward voltage drop of 0.7V.


CIRCUIT DIAGRAM OF BUFFER AND DRIVER


+12 v VIC1

4050IC2

2004

1

8

9

3 2 1 16

+VCC VCC

D1 1N4148

GND

N/O

N/C

N/O

N/C

N/O

N/C

N/O

N/C

5 42 15

7 63 14

1211 5 12

9 10124 13

111115 6

FROM RF / IR ID RECEIVER STAGE

25

Parts List:

SEMICONDUCTORS

D1& D2 1N4148 SIGNAL DIODE 2

IC1 4050 HEX BUFFER / CONVERTER (NON-INVERTER) 1

IC2 2004 DARLINGTON ARRY 1

MISCELLANEOUS

M1 12 V, D.C MOTOR 1

RL1-RL4 12 V, 700 Ohm DPDT Reed Relays 4


The Hex Buffer/Inverter IC1 has six input/outputs but only four are used in the present circuit. The

working voltage of +5V is applied at pin-1 and four control signals are applied at input pins 5, 7, 9 &

11. Thus the signal supplying circuit is isolated from this Buffer & Driver circuit. And the varying input

is further stabilized and fed to signal diodes. As the load may be anything [especially inductive], there

is a chance of producing back e.m.f. So to cope with this back e.m.f, signal diodes are used. But this

signal level is not strong enough to drive the low impedance relay. So, Darlington driver IC2 is used.

Its working voltage is +12 V and only four input/output pins are used. The output signal from the

Darlington driver IC is strong enough to actuate four relays. These relays with +12V working voltage

are used to supply 4-bit RF / IR ID decoded signal to Computer for further processing. That is, each

relays N/O [Normally Open] pins are used state that the particular bit is High.


MOTHER BOARD 89C51

The 89C51 Micro-controller is heart of this project. It is the chip that processes the User Data

and executes the same. The software inherited in this chip manipulates the data and sends

the result for visual display.

INTRODUCTION OF Micro-controller

What is a microcontroller?

The general definition of a microcontroller is a single chip computer, which refers to the fact that

they contain all of the functional sections (CPU, RAM, ROM, I/O, ports and timers) of a traditionally

defined computer on a single integrated circuit. Some experts even describe them as special

purpose computers with several qualifying distinctions that separate them from other computers.

Microcontrollers are "embedded" inside some other device (often a consumer product) so that they

can control the features or actions of the product. Another name for a microcontroller, therefore, is

"embedded controller."

Microcontrollers are dedicated to one task and run one specific program. The program is stored in

ROM (read-only memory) and generally does not change.

Microcontrollers are often low-power devices. A desktop computer is almost always plugged into a

wall socket and might consume 50 watts of electricity. A battery-operated microcontroller might

consume 50 mill watts.

A microcontroller has a dedicated input device and often (but not always) has a small LED or LCD

display for output. A microcontroller also takes input from the device it is controlling and controls the

device by sending signals to different components in the device.

A microcontroller is often small and low cost. The components are chosen to minimize size and to be

as inexpensive as possible.

A microcontroller is often, but not always, ruggedized in some way. The microcontroller controlling a

car's engine, for example, has to work in temperature extremes that a normal computer generally

cannot handle. A car's microcontroller in Kashmir regions has to work fine in -30 degree F (-34 C)

weather, while the same microcontroller in Gujarat region might be operating at 120 degrees F (49

C). When you add the heat naturally generated by the engine, the temperature can go as high as


150 or 180 degrees F (65-80 C) in the engine compartment. On the other hand, a microcontroller

embedded inside a VCR hasn't been ruggedized at all.

Clearly, the distinction between a computer and a microcontroller is sometimes blurred. Applying

these guidelines will, in most cases, clarify the role of a particular device.

Why are they so popular?

The programmability of modern desktop PCs makes them extraordinarily versatile. The functionality

of the entire machine can be altered by merely changing its programming. Microcontrollers share this

attribute with their desktop relatives. The chips are manufactured with powerful capabilities and the

end user determines exactly how the device will function. Often, this makes a dramatic difference in

the cost and complexity of a particular design. The true impact of this statement is best illustrated by

example.

For every clock pulse, the circuit produces one of the three bit numbers in the sequence 000, 100,

111, 010, 011. This design has been implemented with three flip-flops and seven discrete gates as

well as a significant amount of wiring.

The design of this system can be quite laborious. One must begin with a state graph followed by a

state table. Then, the flip-flop T input equations must be derived from a set of Karnaugh maps. Next,

the t input equations must be transformed into the actual T input network. All of this circuitry must

then be wired together; a task that's time consuming and sometimes error prone. On the other hand,

this can be accomplished with a simpler, less costly microcontroller design. Notice the dramatic

difference in the amount of hardware and wiring. This simple circuit, along with about a dozen lines of

code, will perform the same task as the first circuit. There are other benefits as well. The

microcontroller implementation does not have to contend with the undetermined states that

sometimes occur with discrete designs. Also consider for a moment what would be required to

change the sequence of numbers in the first circuit. What if the output needs to be changed to eight

bits instead of three? These are trivial modifications for the microcontroller while the discrete circuit

would require a complete redesign.

The example above is not an obscure case. The effects of this device are being felt in almost every

facet of digital design. A sure method of determining the popularity of an electronic device is to note

when they attain widespread use by hobbyists. It therefore becomes essential that the electronics

engineer or hobbyist learn to program these microcontrollers to maintain a level of competence and

to gain the advantages microcontrollers provide in his or her own circuit designs.


Introducing the Intel’s Microcontroller 89C51

Features

• Compatible with MCS-51™ Products

• 8K Bytes of In-System Reprogrammable Flash Memory

• Endurance: 1,000 Write/Erase Cycles

• Fully Static Operation: 0 Hz to 24 MHz

• Three-level Program Memory Lock

• 256 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Three 16-bit Timer/Counters

• Eight Interrupt Sources

• Programmable Serial Channel

• Low-power Idle and Power-down Modes

Description

The AT89C52 is a low-power, high-performance

CMOS 8-bit microcomputer with 8K bytes of Flash

programmable and erasable read only memory

(PEROM). The device is manufactured using Atmel’s

high-density nonvolatile memory technology and is

compatible with the industry-standard 80C51 and

80C52 instruction set and pin out.

The on-chip Flash allows the program memory to be

reprogrammed in-system or by a conventional

nonvolatile memory programmer. By combining a

versatile 8-bit CPU with Flash on a monolithic chip,

the Atmel AT89C52 is a powerful microcomputer

which provides a highly-flexible and cost-effective

solution to many embedded control applications.

The AT89C52 provides the following standard

features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, a six-vector

two-level interrupt architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry.


In addition, the AT89C52 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 hardware reset.

Pin Description

VCC

Supply voltage.


GND

Ground.

Port 0

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink eight 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 internal pull ups.

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

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

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 four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the internal

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

source current (IIL) because of the internal pull ups.

In addition, 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.

Port 1 also receives the low-order address bytes during Flash programming and verification. Port Pin

Alternate Functions P1.0 T2 (external count input to Timer/Counter 2), clock-out P1.1 T2 EX

(Timer/Counter 2 capture/reload trigger and direction control) AT89C52

Port 2




source current (IIL) because of the 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 uses 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 uses 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.

Port 3




source current (IIL) because of the pull ups.

Port 3 also receives some control signals for Flash programming and verification.

Port Pin Alternate Functions

P3.0 RXD (serial input port)

P3.1 TXD (serial output port)

P3.2 INT0 (external interrupt 0)

P3.3 INT1 (external interrupt 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)

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.

ALE/PROG

Address Latch Enable is an output pulse for latching the low byte of the address during accesses to

external memory. This pin is also the program pulse input (PROG) during Flash programming. In

normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used

for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each

access to external data memory.

If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE

is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting

the ALE-disable bit has no effect if the microcontroller is in external execution mode.


PSEN

Program Store Enable is the read strobe to external program memory. When the AT89C52 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.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device to fetch code

from external program memory locations starting at 0000H up to FFFFH.

Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be

strapped to VCC for internal program executions.

This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming

when 12-volt programming is selected.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

Special Function Registers

A map of the on-chip memory area called the Special Function Register (SFR) space. 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 in general 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 AT89C52 new features. In that case, the reset or inactive values of the new bits

will always be 0.

Timer 2 Register’s Control and status bits are contained in registers T2CON and T2MOD for Timer2.

The register pair (RCAP2H, RCAP2L) is the Capture/Reload registers for Timer 2 in 16-bit capture

mode or 16-bit auto-reload mode.

Interrupt Register

The individual interrupt enable bits are in the IE register. Two priorities can be set for each of the six

interrupt sources in the IP register.r


Symbol Function

TF2 Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2

will not be set when either RCLK = 1 or TCLK = 1.

EXF2 Timer 2 external flag set when either a capture or reload is caused by a negative

transition on T2EX and EXEN2 = 1. When Timer 2 interrupt is enabled, EXF2 = 1 will

cause the CPU to vector to the Timer 2 interrupt routine. EXF2 must be cleared by

software. EXF2 does not cause an interrupt in up/down counter mode (DCEN = 1).

RCLK Receive clock enable. When set, causes the serial port to use Timer 2 overflow pulses

for it’s receive clock in serial port Modes 1 and 3. RCLK = 0 causes Timer 1 overflow to

be used for the receive clock.

TCLK Transmit clock enable. When set, causes the serial port to use Timer 2 overflow pulses

for it’s transmit clock in serial port Modes 1 and 3. TCLK = 0 causes Timer 1 overflows

to be used for the transmit clock.

EXEN2 Timer 2 external enable. When set, allows a capture or reload to occur as a result of a

negative transition on T2EX if Timer 2 is not being used to clock the serial port. EXEN2

= 0 causes Timer 2 to ignore events at T2EX.

TR2 Start/Stop control for Timer 2. TR2 = 1 starts the timer.

C/T2 Timer or counter select for Timer 2. C/T2 = 0 for timer function. C/T2 = 1 for external

event counter (falling edge triggered).

CP/RL2 Capture/Reload select. CP/RL2 = 1 causes captures to occur on negative transitions at

T2EX if EXEN2 = 1. CP/RL2 = 0 causes automatic reloads to occur when Timer 2

overflows or negative transitions occur at T2EX when EXEN2 = 1. When either RCLK or

TCLK = 1, this bit is ignored and the timer is forced to auto-reload on Timer 2 overflow.

Data Memory

The AT89C52 implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a parallel address

space to the Special Function Registers. That means the upper 128 bytes have the same addresses

as the SFR space but are physically separate from SFR space.


When an instruction accesses an internal location above address 7FH, the address mode used in the

instruction specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR space.

Instructions that use direct addressing access SFR space.

For example, the following direct addressing instruction accesses the SFR at location 0A0H (which is

P2).

MOV 0A0H, #data

Instructions that use indirect addressing access the upper 128 bytes of RAM. For example, the

following indirect addressing instruction, where R0 contains 0A0H, accesses the data byte at address

0A0H, rather than P2 (whose address is 0A0H).

MOV @R0, #data

Note that stack operations are examples of indirect addressing, so the upper 128 bytes of data RAM

are available as stack space.

Timer 0 and 1

Timer 0 and Timer 1 in the AT89C52 operate the same way as Timer 0 and Timer 1 in the AT89C51.

Timer 2

Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event counter. The type of

operation is selected by bit C/T2 in the SFR T2CON. Timer 2 has three operating modes: capture,

auto-reload (up or down counting), and baud rate generator. The modes are selected by bits in

T2CON. Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the TL2 register

is incremented every machine cycle. Since a machine cycle consists of 12 oscillator periods, the

count rate is 1/12 of the oscillator frequency.

In the Counter function, the register is incremented in response to a 1-to-0 transition at its

corresponding external input pin, T2. In this function, the external input is sampled during S5P2 of

every machine cycle. When the samples show a high in one cycle and a low in the next cycle, the

count is incremented. The new count value appears in the register during S3P1 of the cycle following

the one in which the transition was detected. Since two machine cycles (24 oscillator periods) are

required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the oscillator frequency.

To ensure that a given level is sampled at least once before it changes, the level should be held for at

least one full machine cycle.

Capture Mode Source: Magnum Technologies.35

In the capture mode, two options are selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2 is a

16-bit timer or counter which upon overflow sets bit TF2 in T2CON.

This bit can then be used to generate an interrupt. If EXEN2 = 1, Timer 2 performs the same

operation, but a 1-to-0 transition at external input T2EX also causes the current value in TH2 and TL2

to be captured into RCAP2H and RCAP2L, respectively. In addition, the transition at T2EX causes bit

EXF2 in T2CON to be set. The EXF2 bit, like TF2, can generate an interrupt.

Auto-reload (Up or Down Counter)

Timer 2 can be programmed to count up or down when configured in its 16-bit auto-reload mode.

This feature is invoked by the DCEN (Down Counter Enable) bit located in the SFR T2MOD. Upon

reset, the DCEN bit is set to 0 so that timer 2 will default to count up. When DCEN is set, Timer 2 can

count up or down, depending on the value of the T2EX pin.

Baud Rate Generator

Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON (Table 2).

Note that the baud rates for transmit and receive can be different if Timer 2 is used for the receiver or

transmitter and Timer 1 is used for the other function. Setting RCLK and/or TCLK puts Timer 2 into its

baud rate generator mode.

The baud rate generator mode is similar to the auto-reload mode, in that a rollover in TH2 causes the

Timer 2 registers to be reloaded with the 16-bit value in registers RCAP2H and RCAP2L, which are

preset by software. The baud rates in Modes 1 and 3 are determined by Timer 2’s overflow rate

according to the following equation.

The Timer can be configured for either timer or counter operation. In most applications, it is

configured for timer operation (CP/T2 = 0). The timer operation is different for Timer 2 when it is used

as a baud rate generator. Normally, as a timer, it increments every machine cycle (at 1/12 the

oscillator frequency).

Note that when Timer 2 is running (TR2 = 1) as a timer in the baud rate generator mode, TH2 or TL2

should not be read from or written to. Under these conditions, the Timer is incremented every state

time, and the results of a read or write may not be accurate. The RCAP2 registers may be read but

should not be written to, because a write might overlap a reload and cause write and/or reload errors.

The timer should be turned off (clear TR2) before accessing the Timer 2 or RCAP2 registers.

Programmable Clock Out Source: Magnum Technologies.36

A 50% duty cycle clock can be programmed to come out on P1.0. This pin, besides being a regular

I/O pin, has two alternate functions. It can be programmed to input the external clock for

Timer/Counter 2

or to output a 50% duty cycle clock ranging from 61 Hz to 4 MHz at a 16 MHz operating frequency.

To configure the Timer/Counter 2 as a clock generator, bit C/T2 (T2CON.1) must be cleared and bit

T2OE (T2MOD.1) must be set. Bit TR2 (T2CON.2) starts and stops the timer.

UART

The UART in the AT89C52 operates the same way as the UART in the AT89C51.

Interrupts

The AT89C52 has a total of six interrupt vectors: two external interrupts (INT0 and INT1), three timer

interrupts (Timers 0, 1, and 2), and the serial port interrupt. Each of these interrupt sources can be

individually enabled or disabled by setting or clearing a bit in Special Function Register IE. IE also

contains a global disable bit, EA, which disables all interrupts at once.

Note that Table shows that bit position IE.6 is unimplemented. In the A T89 C5 1, bit position IE.5 is

also

unimplemented. User software should not write 1s to these bit positions, since they may be used in

future AT89 products.

Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in register T2CON. Neither of

these flags is cleared by hardware when the service routine is vectored to. In fact, the service routine

may have to determine whether it was TF2 or EXF2 that generated the interrupt, and that bit will have

to be cleared in software.

Oscillator Characteristics

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can be

configured for use as an on-chip oscillator, as shown in Figure 7. Either a quartz crystal or ceramic

resonator may be used. To drive the device from an external clock source, XTAL2 should be left

unconnected while XTAL1 is driven.

There are no requirements on the duty cycle of the external clock signal, since the input to the

internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high

and low time specifications must be observed.


Idle Mode

In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active. The mode is

invoked by software. The content of the on-chip RAM and all the special functions registers remain

unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a

hardware reset.

Note that when idle mode is terminated by a hardware reset, the device normally resumes program

execution from where it left off, up to two machine cycles before the internal reset algorithm takes

control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is

not inhibited. To eliminate the possibility of an unexpected write to a port pin when idle mode is

terminated

By a reset, the instruction following the one that invokes idle mode should not write to a port pin or to

external memory.

Power-down Mode

In the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the

last instruction executed. The on-chip RAM and Special Function Registers retain their values until

the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset

redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before

VCC is restored to its normal operating level and must be held active long enough to allow the

oscillator to restart and stabilize.

Programming the Flash

The AT89C52 is normally shipped with the on-chip Flash memory array in the erased state (that is,

contents = FFH) and ready to be programmed. The programming interface accepts either a high-

voltage (12-volt) or a low-voltage (VCC) program enable signal. The Low-voltage programming mode

provides a convenient way to program the AT89C52 inside the user’s system, while the high-voltage

programming mode is compatible with conventional third party Flash or EPROM programmers.

The AT89C52 is shipped with either the high-voltage or low-voltage programming mode enabled.

The AT89C52 code memory array is programmed byte-by-byte in either programming mode. To

program any nonblank byte in the on-chip Flash Memory, the entire memory must be erased using

the


Chip Erase Mode.

Programming Algorithm Before programming the AT89C52, the address, data and control signals

should be set up according to the Flash programming mode table and Figure 9 and Figure 10. To

program the AT89C52, take the following steps.

1. Input the desired memory location on the address lines.

2. Input the appropriate data byte on the data lines.

3. Activate the correct combination of control signals.

4. Raise EA/VPP to 12V for the high-voltage programming mode.

5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write cycle is

self-timed and typically takes no more than 1.5 ms.

Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the

object file is reached.

Data Polling

The AT89C52 features Data Polling to indicate the end of a write cycle. During a write cycle, an

attempted read of the last byte written will result in the complement of the written data on PO.7. Once

the write cycle has been completed, true data is valid on all outputs, and the next cycle may begin.

Data Polling may begin any time after a write cycle has been initiated. Ready/Busy The progress of

byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE

goes high during programming to indicate

BUSY.

P3.4 is pulled high again when programming is done to indicate READY. Program Verify If lock bits

LB1 and LB2 have not been programmed, the programmed code data can be read back via the

address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock

bits is achieved by observing that their features are enabled.

Chip Erase

The entire Flash array is erased electrically by using the proper combination of control signals and by

holding ALE/PROG low for 10 ms. The code array is written with all 1s. The chip erase operation

must be executed before the code memory can be reprogrammed.

Reading the Signature Bytes


The signature bytes are read by the same procedure as a normal verification of locations 030H,

031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned are as

follows.

(030H) = 1EH indicates manufactured by Atmel

(031H) = 52H indicates 89C52

(032H) = FFH indicates 12V programming

(032H) = 05H indicates 5V programming


Flash Programming Modes

Programming Interface

Every code byte in the Flash array can be written, and the entire array can be erased, by using the

appropriate combination of control signals. The write operation cycle is self timed and once initiated,

will automatically time itself to completion.

DC Characteristics

Absolute Maximum Ratings*

Operating Temperature.................................. -55°C to +125°C

Storage Temperature ..................................... -65°C to +150°C

Voltage on Any Pin with Respect to Ground .....................................-1.0V to +7.0V

Maximum Operating Voltage............................................ 6.6V

DC Output Current...................................................... 15.0 mA



Parts List of Power SupplyX1 12-0-12V Transformer 1IC1 7805 Regulator IC 1D1 & D2 1N4007 Rectifier Diode 2D3 Red Indicator LED 1R1 100 KΩ Carbon Resistor 1C1 1000MFD/25V Electrolytic Capacitor 1C2 & C3 0.1µF Ceramic Capacitor 2

COMPLETE CIRCUIT DIAGRAM [MOTHER BOARD] OF 89C51

+Vcc

P0.7

32

P0.6

33

P0.5

34

P0.4

35

P0.3

36

P0.2

37

P0.1

38

P0.0

39

P2.7

28

P2.6

27

P2.5

26

P2.4

25

P2.3

24

P2.2

23

P2.1

22

P2.0

21 1

P1.7

8

P1.6

7

P1.5

6

P1.4

5

P1.3

4

P1.2

3

P1.1

2

P1.0

1 1

19 XTAL1

18 XTAL2

30 pF

12 MHz

30 pF

89C51

VSS

20

29

PSEN

30 ALE

31 EA

9 RST

+VCC

10 MFD/63V

20KΩ RESET

SWITCH

40

VCC

8 x 2.2 KΩ

AD7

AD6

AD5

AD4

AD3

AD2

AD1

AD0

RD

WR

T1

T0

INT1

INT0

TXD

RXD

17

P3.7

16

P3.6

15

P3.5

14

P3.4

13

P3.3

12

P3.2

11

P3.1

10

P3.0

A15

A14

A13

A12

A11

A10

A9

A8

230 AC

X1 D1 & D2 IC1

+VCC

R1

D3

C1 C2 C3

PORT 0

PORT 1

PORT 2PORT 3

42

CIRCUIT DESCRIPTION

The mother board of 89C51 has following sections: Power Supply, 89C51 IC, Oscillator, Reset

Switch & I/O ports. Let us see these sections in detail.

POWER SUPPLY:This section provides the clean and harmonic free power to IC to function properly. The output of the

full wave rectifier section, which is built using two rectifier diodes, is given to filter capacitor. The

electrolytic capacitor C1 filters the pulsating dc into pure dc and given to Vin pin-1 of regulator IC

7805.This three terminal IC regulates the rectified pulsating dc to constant +5 volts. C2 & C3 provides

ground path to harmonic signals present in the inputted voltage. The Vout pin-3 gives constant,

regulated and spikes free +5 volts to the mother board.

The allocation of the pins of the 89C51 follows a U-shape distribution. The top left hand corner is Pin

1 and down to bottom left hand corner is Pin 20. And the bottom right hand corner is Pin 21 and up to

the top right hand corner is Pin 40. The Supply Voltage pin Vcc is 40 and ground pin Vss is 20.

OSCILLATOR:

If the CPU is the brain of the system then the oscillator, or clock, is the heartbeat. It provides the

critical timing functions for the rest of the chip. The greatest timing accuracy is achieved with a crystal

or ceramic resonator. For crystals of 2.0 to 12.0 MHz, the recommended capacitor values should be

in the range of 15 to 33pf2.

Across the oscillator input pins 18 & 19 a crystal x1 of 4.7 MHz to 20 MHz value can be connected.

The two ceramic disc type capacitors of value 30pF are connected across crystal and ground,

stabilizes the oscillation frequency generated by crystal.

I/O PORTS:

There are a total of 32 i/o pins available on this chip. The amazing part about these ports is that they

can be programmed to be either input or output ports, even "on the fly" during operation! Each pin

can source 20 mA (max) so it can directly drive an LED. They can also sink a maximum of 25 Ma

current.

Some pins for these I/O ports are multiplexed with an alternate function for the peripheral features on

the device. In general, when a peripheral is enabled, that pin may not be used as a general purpose

I/O pin. The alternate function of each pin is not discussed here, as port accessing circuit takes care

of that.

This 89C51 IC has four I/O ports and is discussed in detail:


P0.0 TO P0.7

PORT0 is an 8-bit [pins 32 to 39] open drain bi-directional I/O port. As an output port, each pin can

sink eight TTL inputs and configured to be multiplexed low order address/data bus then has internal

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

P1.0 TO P1.7

PORT1 is an 8-bit wide [pins 1 to 8], bi-directional port with internal pull ups. P1.0 and P1.1 can be

configured to be the timer/counter 2 external count input and the timer/counter 2 trigger input

respectively.

P2.0 TO P2.7

PORT2 is an 8-bit wide [pins 21 to 28], bi-directional port with internal pull ups. The PORT2 output

buffers can sink/source four TTL inputs. It receives the high-order address bits and some control

signals during Flash programming and verification.

P3.0 TO P3.7

PORT3 is an 8-bit wide [pins 10 to 17], bi-directional port with internal pull ups. The Port3 output

buffers can sink/source four TTL inputs. It also receives some control signals for Flash programming

and verification.

PSEN

Program Store Enable [Pin 29] is the read strobe to external program memory.

ALE

Address Latch Enable [Pin 30] is an output pulse for latching the low byte of the address during

accesses to external memory.

EA

External Access Enable [Pin 31] must be strapped to GND in order to enable the device to fetch code

from external program memory locations starting at 0000H upto FFFFH.

RST

Reset input [Pin 9] must be made high for two machine cycles to resets the device’s oscillator. The

potential difference is created using 10MFD/63V electrolytic capacitor and 20KOhm resistor with a

reset switch.


LCD INTERFACING

LCDs can add a lot to any application in terms of providing an useful interface for the user, debugging

an application or just giving it a "professional" look. The most common type of LCD controller is the

Hitatchi 44780 which provides a relatively simple interface between a processor and an LCD. Using

this interface is often not attempted by inexperienced designers and programmers because it is

difficult to find good documentation on the interface, initializing the interface can be a problem and

the displays themselves are expensive.

The most common connector used for the 44780 based LCDs is 14 pins in a row, with pin centers

0.100" apart. The pins are wired as:

Pins Description

1 Ground

2 Vcc

3 Contrast Voltage

4 "R/S" _Instruction/Register Select

5 "R/W" _Read/Write LCD Registers

6 "E" Clock

7 - 14 Data I/O Pins

The interface is a parallel bus, allowing simple and fast reading/writing of data to and from the LCD.

The LCD Data Write Waveform will write an ASCII Byte out to the LCD's screen. The ASCII code to

be displayed is eight bits long and is sent to the LCD either four or eight bits at a time. If four bit mode

is used, two "nibbles" of data (Sent high four bits and then low four bits with an "E" Clock pulse with

each nibble) are sent to make up a full eight bit transfer. The "E" Clock is used to initiate the data

transfer within the LCD.

Sending parallel data as either four or eight bits are the two primary modes of operation. While there

are secondary considerations and modes, deciding how to send the data to the LCD is most critical

decision to be made for an LCD interface application.

Eight bit mode is best used when speed is required in an application and at least ten I/O pins are

available. Four bit mode requires a minimum of six bits. To wire a microcontroller to an LCD in four bit

mode, just the top four bits (DB4-7) are written to.


DATA

R/_S

R/_W

E

450 nSec

LCD DATA WRITE WAVEFORM

45

The "R/S" bit is used to select whether data or an instruction is being transferred between the

microcontroller and the LCD. If the Bit is set, then the byte at the current LCD "Cursor" Position can

be read or written. When the Bit is reset, either an instruction is being sent to the LCD or the

execution status of the last instruction is read back (whether or not it has completed).

The different instructions available for use with the 44780 are shown in the table below:

R/S R/W D7 D6 D5 D4 D3 D2 D1 D0 Instruction/Description

4 5 14 13 12 11 10 9 8 7 Pins

0 0 0 0 0 0 0 0 0 1 Clear Display

0 0 0 0 0 0 0 0 1 * Return Cursor and LCD to Home Position

0 0 0 0 0 0 0 1 ID S Set Cursor Move Direction

0 0 0 0 0 0 1 D C B Enable Display/Cursor

0 0 0 0 0 1 SC RL * * Move Cursor/Shift Display

0 0 0 0 1 DL N F * * Set Interface Length

0 0 0 1 A A A A A A Move Cursor into CGRAM

0 0 1 A A A A A A A Move Cursor to Display

0 1 BF * * * * * * * Poll the "Busy Flag"

1 0 D D D D D D D D Write a Character to the Display at the Current Cursor Position

1 1 D D D D D D D D Read the Character on the Display at the Current Cursor Position

The bit descriptions for the different commands are:

"*" - Not Used/Ignored. This bit can be either "1" or "0"

Set Cursor Move Direction:

ID - Increment the Cursor After Each Byte Written to Display if Set

S - Shift Display when Byte Written to Display

Enable Display/Cursor

D - Turn Display On(1)/Off(0)

C - Turn Cursor On(1)/Off(0)

B - Cursor Blink On(1)/Off(0)

Move Cursor/Shift Display

SC - Display Shift On(1)/Off(0)

RL - Direction of Shift Right(1)/Left(0)

Set Interface Length


DL - Set Data Interface Length 8(1)/4(0)

N - Number of Display Lines 1(0)/2(1)

F - Character Font 5x10(1)/5x7(0)

Poll the "Busy Flag"

BF - This bit is set while the LCD is processing

Move Cursor to CGRAM/Display

A - Address

Read/Write ASCII to the Display

D - Data

Before you can send commands or data to the LCD module, the Module must be initialized. For eight

bit mode, this is done using the following series of operations:

Wait more than 15 mSecs after power is applied.

Write 0x030 to LCD and wait 5 mSecs for the instruction to complete

Write 0x030 to LCD and wait 160 µsecs for instruction to complete

Write 0x030 AGAIN to LCD and wait 160 µsecs or Poll the Busy Flag

Set the Operating Characteristics of the LCD

Write "Set Interface Length"

Write 0x010 to turn off the Display

Write 0x001 to Clear the Display

Write "Set Cursor Move Direction" Setting Cursor Behaviour Bits

Write "Enable Display/Cursor" & enable Display and Optional Cursor

In describing how the LCD should be initialized in four bit mode, experts will specify writing to the

LCD in terms of nibbles. This is because initially, just single nibbles are sent (and not two, which

make up a byte and a full instruction). As mentioned above, when a byte is sent, the high nibble is

sent before the low nibble and the "E" pin is toggled each time four bits is sent to the LCD. To

initialize in four bit mode:

Wait more than 15 mSecs after power is applied.

Write 0x03 to LCD and wait 5 mSecs for the instruction to complete

Write 0x03 to LCD and wait 160 µsecs for instruction to complete

Write 0x03 AGAIN to LCD and wait 160 µsecs (or poll the Busy Flag)

Set the Operating Characteristics of the LCD

Write 0x02 to the LCD to Enable Four Bit Mode

All following instruction/Data Writes require two nibble writes.


Write "Set Interface Length"

Write 0x01/0x00 to turn off the Display

Write 0x00/0x01 to Clear the Display

Write "Set Cursor Move Direction" Setting Cursor Behaviour Bits

Write "Enable Display/Cursor" & enable Display and Optional Cursor

Once the initialization is complete, the LCD can be written to with data or instructions as required.

Each character to display is written like the control bytes, except that the "R/S" line is set. During

initializiation, by setting the "S/C" bit during the "Move Cursor/Shift Display" command, after each

character is sent to the LCD, the cursor built into the LCD will increment to the next position (either

right or left). Normally, the "S/C" bit is set (equal to "1") along with the "R/L" bit in the "Move

Cursor/Shift Display" command for characters to be written from left to right (as with a "Teletype"

video display).

Most LCD displays have a 44780 and support chip to control the operation of the LCD. The 44780 is

responsible for the external interface and provides sufficient control lines for sixteen characters on

the LCD. The support chip enhances the I/O of the 44780 to support up to 128 characters on an LCD.

From the table above, it should be noted that the first two entries ("8x1", "16x1") only have the 44780

and not the support chip. This is why the ninth character in the 16x1 does not "appear" at address 8

and shows up at the address that is common for a two line LCD.

Here it is included the 40 character by 4 line ("40x4") LCD because it is quite common. Normally, the

LCD is wired as two 40x2 displays. The actual connector is normally sixteen bits wide with all the

fourteen connections of the 44780 in common, except for the "E" (Strobe) pins. The "E" strobes are

used to address between the areas of the display used by the two devices. The actual pinouts and

character addresses for this type of display can vary between manufacturers and display part

numbers.

Note that when using any kind of multiple 44780 LCD display, programmer should probably only

display one 44780's Cursor at a time.

Cursors for the 44780 can be turned on as a simple underscore at any time using the "Enable

Display/Cursor" LCD instruction and setting the "C" bit. Expert don't recommend using the "B" ("Block

Mode") bit as this causes a flashing full character square to be displayed and it really isn't that

attractive.


The LCD can be thought of as a "Teletype" display because in normal operation, after a character

has been sent to the LCD, the internal "Cursor" is moved one character to the right. The "Clear

Display" and "Return Cursor and LCD to Home Position" instructions are used to reset the Cursor's

position to the top right character on the display.

To move the Cursor, the "Move Cursor to Display" instruction is used. For this instruction, bit 7 of the

instruction byte is set with the remaining seven bits used as the address of the character on the LCD

the cursor is to move to. These seven bits provide 128 addresses, which matches the maximum

number of LCD character addresses available. The table above should be used to determine the

address of a character offset on a particular line of an LCD display.

The Character Set available in the 44780 is basically ASCII. It is "basically" because some characters

do not follow the ASCII convention fully (probably the most significant difference is 0x05B or "\" is not

available). The ASCII Control Characters (0x008 to 0x01F) do not respond as control characters and

may display funny (Japanese) characters.

The last aspect of the LCD to discuss is how to specify a contrast voltage to the Display. Experts

typically use a potentiometer wired as a voltage divider. This will provide an easily variable voltage

between Ground and Vcc, which will be used to specify the contrast (or "darkness") of the characters

on the LCD screen. You may find that different LCDs work differently with lower voltages providing

darker characters in some and higher voltages do the same thing in others.

There are a variety of different ways of wiring up an LCD. Above, it is noted that the 44780 can

interface with four or eight bits. To simplify the demands in microcontrollers, a shift register is often

used (as is shown in the diagram below) to reduce the number of I/O pins to three.


LCD Contrast Circuit

+Vcc

Pin-3 Contrast

LCD10K pot

Shift Register LCD Data Write

R6D0D1

Dn

E

LCD

E Clock

S/R

Processor

Data

DataClock

00

49

It is evident that using this circuit with the PICMicro, 8051 and AVR and it really makes the wiring of

an LCD to a microcontroller very simple. A significant advantage of using a shift register, like the two

circuits shown here, data to the LCD is the lack of timing sensitivity that will be encountered. The

biggest issue to watch for is to make sure the "E" Strobe's timing is within specification (i.e., greater

than 450 nSecs), the shift register loads can be interrupted without affecting the actual write. This

circuit will not work with Open-Drain only outputs.

One note about the LCD's "E" Strobe is that in some documentation it is specified as "high" level

active while in others, it is specified as falling edge active. It seems to be falling edge active, which is

why the 2-wire LCD interface presented below works even if the line ends up being high at the end of

data being shifted in. If the falling edge is used (like in the 2-wire interface) then make sure that

before the "E" line is output on "0", there is at least a 450 nSecs delay with no lines changing state.

Next the program is given in 8051 assembly language with necessary comments that can display a

message or single character on screen.

com equ 0fch ; command follows this headerdat equ 0fdh ; Data follows this headereof equ 0feh ; End of message

org 00h

mov dptr,#2000h ; Initilize LCD and display message

acall msg ; "Wel - Come To

mov a,#c0h ; Go to the next line

acall cmmd

mov a,#'L' ; and display character 'L'

acall dis

mov a,#'C' ; and display character 'C'

acall dis

mov a,#'D' ; and display character 'D'

acall dis

mov dptr,#3000h ; display word 'program' in next line

acall msg ; after character 'D'.

here: sjmp here ; continue loopSource: Magnum Technologies.50

msg: acall ready ; wait until display is busy clr a movc a,@a+dptr ; get the character inc dptr ; point to next character cjne a,#eof,cmd ; if end of message then ret ; return from sub routinecmd:cjne a,#com,data ; if command then DI (RS) = 0 clr p0.1 sjmp msg ; go until donedata:cjne a,#dat,send ; if data then DI (RS) = 1 setb p0.1 sjmp msg ; go until donesend: mov p1,a ; send data/command to display clr p0.2 ; write enable setb p0.0 ; strobe character to display clr p0.0 sjmp msg ; go until done

cmmd: acall ready ; wait until display is busy mov p1,a ; command chara. in p1 clr p0.1 ; select com. register clr p0.2 ; write enable setb p0.0 ; strobe the chara. clr p0.0 retdis: acall ready ; wait until display is busy mov p1,a ; data chara. in p1 setb p0.1 ; select data register clr p0.2 ; write enable setb p3.7 ; strobe the chara. clr p3.7 ret ready: mov r7,p0 ; save content of P0 clr p0.0 ; disable display clr p0.1 ; select command register setb p0.2 ; read enable wait:clr p0.0 ; strobe display setb p0.0 ; read busy status of display jb p1.7,wait ; wait for busy clr p3.7 mov p0,r7 ; restore content of P0 ret

org 2000h ; messages are stored atdb com ; locations 2000h and 3000hdb 3chdb 0fhdb 01h


db datdb 'Wel-Come To'db eof

org 3000h db com db 0c5h db dat db 'Program' db eof

end

PRODUCT SPECIFICATIONS

General

The LCD of the unit is STN (Super Twisted Nematic) Gray , Transflective type.

Low power consumption with the dot-matrix LCD panel and CMOS LSI.

Built-in backlight LED with high luminance and stable radiation.

Thin, lightweight design permits easy installation in a variety of equipment.

Allowing for being connected at general-purpose CMOS signal level, the unit can be easily

interfaced to a microprocessor with common 4-bit and 8-bit parallel inputs and outputs.

Multiplexing driving : 1/16duty, 1/4bias, 6 o’clock

Built-in character generator ROM and RAM, and display data RAM:

Character generator ROM 225 different 5 x 7 dot-matrix character patterns (Alphanumeric and

symbols)

Character generator RAM 8 different user programmed 5 x 7 dot-matrix patterns

Display data RAM 80 x 8 bits

Numerous instructions Display clear, Cursor home, Display ON/OFF, Cursor ON/OFF, Blink

character, Cursor shift, Display shift

The unit operates from a single 5V power supply

Liquid crystal panel service life 100,000 hours minimum at 25 oC -10 oC

3.3 definition of panel service life

Contrast becomes 30% of initial value

Current consumption becomes three times higher than initial value

Remarkable alignment deterioration occurs in LCK cell layer

Unusual operation occurs in display functions

Safety


If the LCD panel breaks, be careful not to get the liquid crystal in your mouth. If the liquid crystal

touches your skin or clothes, wash it off immediately using soap and plenty of water.

Handling

Avoid static electricity as this can damage the CMOS LSI.

The LCD panel is plate glass; do not hit or crush it.

Do not remove the panel or frame from the module.

The polarizing plate of the display is very fragile; handle it very carefully

Mounting and Design

Mount the module by using the specified mounting part and holes.

To protect the module from external pressure, leave a small gap by placing transparent plates (e.g.

acrylic or glass) on the display surface, frame, and polarizing plate

Design the system so that no input signal is given unless the power-supply voltage is applied.

Keep the module dry. Avoid condensation; otherwise the transparent electrodes may break.

Storage

Store the module in a dark place, where the temperature is 25 oC - 10 oC and the humidity below

65% RH.

Do not store the module near organic solvents or corrosive gases.

Do not crush, shake, or jolt the module (including accessories).


VARIABLE POWER SOURCE

Introduction: The power supply, unsung hero of every electronic circuit, plays very important role

in smooth running of the connected circuit. The main object of this ‘variable power supply’ is, as the

name itself implies, to deliver the required amount of stabilized and pure power to the circuit. Every

typical power supply contains the following sections:

1. Step-down Transformer: The conventional supply, which is generally available to the user, is

230V AC. It is necessary to step down the mains supply to the desired level. This is achieved by

using suitably rated step-down transformer. While designing the power supply it is necessary to go

for higher rating transformer than the required one. There are three reasons for this. First reason is,

across the secondary winding of the transformer there is no guarantee of getting the equal voltages.

Secondly, for proper working of the regulator IC it needs at least 2.5V more than the expected output

voltage. Last reason is to compensate the power loss offered by the transformer windings and power

supply circuit itself.

2. Rectifier stage: Then the step-downed Alternating Current is converted into Direct

Current. This rectif ication is achieved by using passive components such as diodes. If

the power supply is designed for high voltage/current drawing loads/circuits bridge rectifier is

employed.

3. Filter stage: But this rectified output contains some percentage of superimposed a.c. ripples. So

to filter these a.c. components filter stage is built around the rectifier stage. The cheap, reliable,

simple and effective filtering for low current drawing loads is done by using shunt capacitors. As this

electrolytic capacitor has polarity, care should be taken while rig-upping the circuit.

4. Voltage Regulation: The filtered d.c. output is not stable. It varies in accordance with the

fluctuations in mains supply or varying load current. This variation of load current is observed due to

voltage drop in transformer windings, rectifier and filter circuit. These variations in d.c. output voltage

may cause inaccurate or erratic operation or even malfunctioning of many electronic circuits. For

example, the circuit boards which are implanted by CMOS or TTL ICs.

The stabilization of d.c. output is achieved by using the three terminal voltage regulator IC. In their

basic operational mode, these regulators require virtually no external components. They are available

in both fixed voltage as well as adjustable voltage types with current ratings of 100mA,


500mA, 1.0A and 3.0A. The fixed types are 78XX & 79XX series, while adjustable types are of

LM117/LM217/LM317 series.

Voltage Regulator LM317: The LM117/LM217/LM317 series adjustable 3-terminal positive voltage

regulators are available in the current ratings of 0.1A, 0.5A and 1.0A. The output voltage is adjustable

from 1.2V to 37V. For LM317 operational temperature range is 0C to +125C. Their performance

specifications are much better than those of fixed voltage regulators. Since these regulators are

floating, and see only the input-to-output differential voltage, supplies of several hundred volts can be

regulated as long as the input-output differential is not exceeded. These regulator ICs have in-built

short-circuit protection and auto-thermal cut-out provisions. If the load current is very high the IC

needs ‘heat sink’ to dissipate the internally generated power.

0-30V THREE TERMINAL VOLTAGE REGULATOR IC: LM 317T

GENERAL CHARACTERISTICS:

1. Output voltage : +1.2V - +37 V

2. Operating Temperature : 0 c - +125 c

3. Output Current : 1 A Max

4. Dropout Voltage : 1.7V – 3V

CIRCUIT DIAGRAM OF 0-30V REGULATED VARIABLE POWER SUPPLY


C3

IN230V AC

C1

D31

X1

D1 D21

D41

LM317T

ADJ

OUT

C2R1

R2

C4

+1.25 TO 30V1AMP

GND

P1

A

B

C D

1 2 3

Adjust

55

Parts List:

SEMICONDUCTORS

IC1 LM317T Regulator IC 1

D1to D4 1N5401 Rectifier Diodes 4



P1 1 K Ohm Preset 1

C1 1000 µf/25V Electrolytic 1

C2 0.1µF Tantalum type 1

C3 10 µF/25V Electrolytic 1

C4 22 µF/40V Electrolytic 1

MISCELLANEOUS

X1 230V AC Pri,0-34V 1Amp Sec Transformer 1

Circuit Description: A d.c. power supply which maintains the output voltage constant

irrespective of a.c. mains fluctuations or load variations is known as regulated d.c. power supply. It

is also referred as full-wave regulated power supply as it uses four diodes in bridge fashion with the

transformer. This laboratory power supply offers excellent line and load regulation and an output

voltage continuously variable from 0 to 30 at output currents up to one amp.

1.Step-down Transformer : The transformer rating is 230V AC at Primary and 0-32V, 1Ampers

across secondary winding. This transformer has a capability to deliver a current of 1Ampere, which is

more than enough to drive any electronic circuit or varying load. The 32VAC appearing across the

secondary is the RMS value of the waveform and the peak value would be 32 x 1.414 = 45.2 volts.

This value limits our choice of rectifier diode as 1N5401, which is having PIV rating more than

45Volts.

2. Rectifier Stage : The four diodes D1to D4 are connected across the secondary winding of the

transformer in bridge fashion to form a full-wave rectifier. During the positive half-cycle of secondary

voltage, the end A of the secondary winding becomes positive and end B negative. This makes the

diode D2 & D3 forward biased and diode D1 & D4 reverse biased. Therefore the series diodes D2 &


D3 provides full wave rectification to produce a positive output. Thus, +30V pulsating d.c. is obtained

at point ‘C’ with respect to Ground. During the negative half-cycle, end A

of the secondary winding becomes negative and end B positive. Therefore diode D1 & D4 are

forward biased and diode D2 & D3 are reverse biased. Hence the series diodes D1 & D4 provides full

wave rectification to produce a negative output. Thus, -30V pulsating d.c. is obtained at point ‘C’ with

respect to Ground.

3.Filter Stage : Here Capacitors C1 is used for filtering purposes and connected across the

rectifier output. It filters the a.c. components present in the rectified d.c. and gives steady d.c. voltage.

As the rectifier voltage increases, it charges the capacitor and also supplies current to the load. When

capacitor is charged to the peak value of the rectifier voltage, rectifier voltage starts to decrease. As

the next voltage peak immediately recharges the capacitor, the discharge period is of very small

duration. Due to this continuous charge-discharge-recharge cycle very little ripple is observed in the

filtered output. Moreover, output voltage is higher as it remains substantially near the peak value of

rectifier output voltage.

4. Voltage Regulation Stage: Across the point ‘D’ with respect to Ground one can measure

rectified and filtered +30V d.c. As the present circuit supplies 0-30 variable voltages the voltage

regulator IC LM317T is used. The rectified & filtered d.c. is connected to pin1 of the regulator IC. The

stabilized d.c. output is given to the load through pin 3 of LM317. The circuit also shows one

decoupling capacitor C2, which provides ground path to the high frequency noise signals. This C2

must preferably be 0.1F tantalum capacitor. The Vref at pin-2 is typically 1.25V and the current

flowing through C3 [Iadj] is 50 µA. The electrolytic capacitor C3 provides ripple rejection C3 to 10F

provides typically 80dB rejection. At out point 0 to 30V stabilized or regulated d.c output is

measured. The output voltage may be adjusted using P1. To set the output voltage to zero P1 Is

first turned anti-clockwise and P2 turned fully clockwise the output voltage should then be

approximately 30 V. If, due to component tolerance, the maximum output is less than 30V the value

of R1 may require slight reduction. When constructing the circuit particular care should be taken to

ensure that the 0 V rail is of low resistance (heavy gauge wire or wide p.c.b.track) as voltage drops

along this line can cause poor regulation and ripple at the output.

Note: While connecting the diodes and electrolytic capacitors the polarities must be taken into

consideration. The transformer’s primary winding deals with 230V mains, care should be taken with it.


REDUCED POWER SOURCE

CIRCUIT DIAGRAM OF +5V FULL WAVE REGULATED POWER SUPPLY

Parts List:

Circuit Description: A d.c. power supply which maintains the output voltage constant

irrespective of a.c. mains fluctuations or load variations is known as regulated d.c. power supply. It

is also referred as full-wave regulated power supply as it uses two diodes in full wave fashion with

centre tap transformer.

1.Step-down Transformer : The transformer rating is 230V AC at Primary and 12-0-12V,

1Ampers across secondary winding. This transformer has a capability to deliver a current of

1Ampere, which is more than enough to drive any electronic circuit or varying load. The 12VAC


SEMICONDUCTORS

IC1 7805 Regulator IC 1

D1,D2 1N4007 Rectifier Diodes 2

CAPACITORS


C2,C3 0.1µF Ceramic Disc type 2

MISCELLANEOUS

X1 230V AC Pri,12-0-12 1Amp Sec

Transformer

1

+5V

B

230 AC

X1

0 V

IC 1

C1

D2 221

C2C3

D1 111

A

O

C D

Ground

E

58

appearing across the secondary is the RMS value of the waveform and the peak value would be 12 x

1.414 = 16.8 volts. This value limits our choice of rectifier diode as 1N4007, which is having PIV

rating more than 16Volts.

2. Rectifier Stage : The two diodes D1 & D2 are connected across the secondary winding of the

transformer as a full-wave rectifier. During the positive half-cycle of secondary voltage, the end A of

the secondary winding becomes positive and end B negative. This makes the diode D1 forward

biased and diode D2 reverse biased. Therefore diode D1 conducts while diode D2 does not. During

the negative half-cycle, end A of the secondary winding becomes negative and end B positive.

Therefore diode D2 conducts while diode D1 does not. Note that current across the centre tap

terminal is in the same direction for both half-cycles of input a.c. voltage. Therefore, pulsating d.c. is

obtained at point ‘C’ with respect to Ground.

3.Filter Stage : Here Capacitor C1 is used for filtering purpose and connected across the rectifier

output. It filters the a.c. components present in the rectified d.c. and gives steady d.c. voltage. As the

rectifier voltage increases, it charges the capacitor and also supplies current to the load. When





rectifier output voltage. This phenomenon is also explained in other form as: the shunt capacitor

offers a low reactance path to the a.c. components of current and open circuit to d.c. component.

During positive half cycle the capacitor stores energy in the form of electrostatic field. During negative

half cycle, the filter capacitor releases stored energy to the load.

4.Voltage Regulation Stage : Across the point ‘D’ and Ground there is rectified and filtered d.c.

In the present circuit KIA 7805 voltage regulator IC is used to get +5V regulated d.c. output. In the

three terminals, pin 1 is input i.e., rectified & filtered d.c. is connected to this pin. Pin 2 is common pin

and is grounded. The pin 3 gives the stabilized d.c. output to the load. The circuit shows two more

decoupling capacitors C2 & C3, which provides ground path to the high frequency noise signals.

Across the point ‘E’ and ground +5V stabilized or regulated d.c output is measured, which can be

connected to the required circuit.

Note: While connecting the diodes and electrolytic capacitors the polarities must be taken into

consideration. The transformer’s primary winding deals with 230V mains, care should be taken with it.


POWER SUPPLY UNIT

The circuit needs two different voltages, +5V & +12V, to work. These dual voltages are supplied by

this specially designed power supply.

The power supply, unsung hero of every electronic circuit, plays very important role in smooth

running of the connected circuit. The main object of this ‘power supply’ is, as the name itself implies,

to deliver the required amount of stabilized and pure power to the circuit. Every typical power supply

contains the following sections:

1. Step-down Transformer: The conventional supply, which is generally available to the user, is 230V

AC. It is necessary to step down the mains supply to the desired level. This is achieved by using

suitably rated step-down transformer. While designing the power supply, it is necessary to go for little

higher rating transformer than the required one. The reason for this is, for proper working of the

regulator IC (say KIA 7812) it needs at least 2.5V more than the expected output voltage

2. Rectifier stage: Then the step-downed Alternating Current is converted into Direct Current. This

rectification is achieved by using passive components such as diodes. If the power supply is

designed for low voltage/current drawing loads/circuits (say +12V), it is sufficient to employ full-wave

rectifier with centre-tap transformer as a power source. While choosing the diodes the PIV rating is

taken into consideration.

3. Filter stage: But this rectified output contains some percentage of superimposed

a.c. ripples. So to filter these a.c. components filter stage is built around the rectifier

stage. The cheap, reliable, simple and effective filtering for low current drawing loads

(say upto 50 mA) is done by using shunt capacitors. This electrolytic capacitor has

polarities, take care while connecting the circuit.

4. Voltage Regulation: The filtered d.c. output is not stable. It varies in accordance

with the fluctuations in mains supply or varying load current. This variation of load

current is observed due to voltage drop in transformer windings, rectifier and filter

circuit. These variations in d.c. output voltage may cause inaccurate or erratic

operation or even malfunctioning of many electronic circuits. For example, the circuit boards which

are implanted by CMOS or TTL ICs.

The stabilization of d.c. output is achieved by using the three terminal voltage regulator IC. This

regulator IC comes in two flavors: 78xx for positive voltage output and 79xx for negative voltage

output. For example 7812 gives +12V output and 7912 gives -12V stabilized output. These regulator


1 2 3

KIA 78xxSeries

60

ICs have in-built short-circuit protection and auto-thermal cutout provisions. If the load current is very

high the IC needs ‘heat sink’ to dissipate the internally generated power.

CIRCUIT DIAGRAM OF +5V & +12V FULL WAVE REGULATED POWER SUPPLY

Parts List:

SEMICONDUCTORS

IC1

IC2

7812 Regulator IC

7805 Regulator IC

1

1

D1& D2 1N4007 Rectifier Diodes 2

CAPACITORS


C2 to C4 0.1µF Ceramic Disc type 3

MISCELLANEOUS

X1 230V AC Pri,14-0-14 1Amp Sec Transformer 1


A d.c. power supply which maintains the output voltage constant irrespective of a.c. mains

fluctuations or load variations is known as regulated d.c. power supply. It is also referred as full-wave


X1

C1

D21

C2 C3

IC17812

D11

C4

9V

IC17805

+12V

+5V

61

regulated power supply as it uses four diodes in bridge fashion with the transformer. This laboratory

power supply offers excellent line and load regulation and output voltages of +5V & +12 V at output

currents up to one amp.

1. Step-down Transformer: The transformer rating is 230V AC at Primary and 12-0-12V, 1Ampers

across secondary winding. This transformer has a capability to deliver a current of 1Ampere, which is

more than enough to drive any electronic circuit or varying load. The 12VAC appearing across the

secondary is the RMS value of the waveform and the peak value would be 12 x 1.414 = 16.8 volts.

This value limits our choice of rectifier diode as 1N4007, which is having PIV rating more than

16Volts.

2. Rectifier Stage: The two diodes D1 & D2 are connected across the secondary winding of the

transformer as a full-wave rectifier. During the positive half-cycle of secondary voltage, the end A of

the secondary winding becomes positive and end B negative. This makes the diode D1 forward

biased and diode D2 reverse biased. Therefore diode D1 conducts while diode D2 does not. During

the negative half-cycle, end A of the secondary winding becomes negative and end B positive.

Therefore diode D2 conducts while diode D1 does not. Note that current across the centre tap

terminal is in the same direction for both half-cycles of input a.c. voltage. Therefore, pulsating d.c. is

obtained at point ‘C’ with respect to Ground.

3. Filter Stage: Here Capacitor C1 is used for filtering purpose and connected across the rectifier

output. It filters the a.c. components present in the rectified d.c. and gives steady d.c. voltage. As the

rectifier voltage increases, it charges the capacitor and also supplies current to the load. When





rectifier output voltage. This phenomenon is also explained in other form as: the shunt capacitor

offers a low reactance path to the a.c. components of current and open circuit to d.c. component.

During positive half cycle the capacitor stores energy in the form of electrostatic field. During negative

half cycle, the filter capacitor releases stored energy to the load.

4. Voltage Regulation Stage: Across the point ‘D’ and Ground there is rectified and filtered d.c. In the

present circuit KIA 7812 three terminal voltage regulator IC is used to get +12V and KIA 7805 voltage

regulator IC is used to get +5V regulated d.c. output. In the three terminals, pin 1 is input i.e., rectified

& filtered d.c. is connected to this pin. Pin 2 is common pin and is grounded. The pin 3 gives the

stabilized d.c. output to the load. The circuit shows two more decoupling capacitors C2 & C3, which


provides ground path to the high frequency noise signals. Across the point ‘E’ and ‘F’ with respect to

ground +5V & +12V stabilized or regulated d.c output is measured, which can be connected to the

required circuit.

4.Project Construction Guidelines

Read these hints carefully before start building your Project. Allow sufficient time to read & be sure

you understand everything perfectly. Start your work where you can be comfortable and can leave

the Project spread out between wiring sessions. Be cool & have patient... project construction should

be educative and fun! Stopping at the end of the every stage and checking, step-by-step, will help

you avoid needless mistakes. This can save you a lot of double checking and time consuming

trouble-shooting later on. Before start assembling the Project, read some basic electronic theory

about active & passive components, how they work, parameters, lead identifications etc. At one

session, work only as long as you enjoys it.

Unpacking the Project Kit:

Unpack the project carefully and check each component against the Component List.

Observe the PCB, Circuit diagram sheet & components for any physical damages.

Check that you got the Project Kit you actually intended for!

Assembling the Project Kit:

Before starts assembling the project keep all the necessary needed tools on your workbench.

Check the PCB for the broken tracks, by testing continuity between each track.

By holding the PCB slightly inclined towards the light, one can check the copper layout’s physical

condition on the PCB.

Identify each section of the circuit on the PCB layout & get familiar with the board.

Check each component & be assuring that they are in good and working condition.

Special care should be taken while dealing with the sensors or sparingly available components.

Clean the component leads, tracks (if they are coated with corrosive layer), and pads.

Soldering the Project Kit

Before start soldering keep all the necessary tools required for it viz., suitably rated Soldering Iron

with clean tip, tweezers, nose-pliers, small & medium size screw drivers, flux, sharp knife etc.


The PCB has two sides. One is the copper foil side and the other, the component side. You have

to mount the components on the component side, solder them on the copper layout side.

Keep below points in memory while soldering

Remember that 90% of all non-functioning of project are due to bad soldering & poor

connections.

Switch OFF the fan, if it is running! Position the work so that gravity tends to keep the solder

where you want it.

The new soldering irons tip should be filed to remove the steel or copper oxide coating. Then

apply little solder on the hot tip.

The soldering iron will reach its operating temperature within 3 to 5 minutes, after it is switched

on, and should be left on during the working period.

For good soldered connections, you must keep the soldering iron tip clean- wipe it often with a

damp sponge or cloth.

Keep hot tip of the soldering iron on a piece of metal so that excess heat is dissipated.

Make sure that the connection to be soldered is clean. Wax frayed insulation’s and other

foreign substances cause poor connections. Clean the component leads wires, lugs, etc., with

a blade or a knife to remove the rust and dust before soldering.

Bend the lead at a 45 angle to the PCB.

Use just enough solder to cover the lead and the copper foil area of the connection to be

soldered. Excess solder can bridge across from one foil path to another foil and cause a short

circuit.

Apply enough heat to the foil and the lead to allow the solder to spread freely. A good soldered

joint will look smooth, shining and solder equally spreaded along the pad.

Do not over heat the components or the PCB. Excess heat may spoil the PCB or damage the

components. The general time of soldering is 2 to 3 seconds.

The PCB or components should not vibrate while soldering otherwise you will have a dry or a

cold joint.

Remember larger metal surfaces take longer time to heat e.g. clamps of Coils, transformers,

heat sinks etc.

While using the ‘de-soldering pump’ to clear the plugged holes/pads special care should be

taken, as the excessive heat or pulling action may damage the copper foils.

The leads of resistors, capacitors, and similar components are generally much longer than

needed to make the required connections. Cut the leads with a diagonal cutter or a nail cutter to

the proper length before installing the part; the leads should be just long enough to reach their

connecting points.

Apply small amount of flux to the tinned & cleaned leads of the soldering components.


Start soldering your Project Kit from the power-supply section viz, step-down transformer, diodes,

capacitors & regulators. First check the components, clean them, and then solder one-by-one on

the PCB. Next step is to check the voltages at different points, across transformer primary &

secondary windings, after rectifier stage, filter stage & regulator stage respectively. Also check

that this voltage is available at all points of the PCB, especially IC’s +Vcc pins.

Now solder the next section of your circuit and check for its integrity with the whole project. This

step-by-step procedure must continue throughout the project building session.

While soldering the order (usually from big-in-size towards small-in-size components) must be IC

bases, transformers, transistors, electrolytic capacitors, coils, ceramic capacitors, resistors etc.

While soldering the sensors, special modules care should be taken that they are not connected in

the reverse order or wrong polarity insertion took place.

To prepare a length of connecting wire or jumper wire, you will normally remove 4mm of insulation

from each end. For stranded wire, apply solder to the ends to hold the strands together.

Resistors should be mounted in either vertical or horizontal fashion. Check the color code for the

proper value before soldering them.

Observe the polarity of the electrolytic capacitors & values of the MKT, Ceramic Disc type

capacitors. Push the leads of the capacitors into the holes until you cannot push them further.

Bend the leads a little, solder and cut off excess lead lengths.

Check the transistors type, whether NPN or PNP, and identify the pins correctly on the PCB.

The band indicates Cathode in Diodes, + mark indicates positive polarity in Capacitors, dot or

notch indicates the Collector lead of the Transistor.

Calibration/Fine Tuning/Adjusting/Aligning the Project Kit

When the whole circuit is soldered and tested for integrity in step-by-step procedure as explained

above, take a break!

This must be a fresh, new session for you. Because this session demands your cool and fresh

mind-set, as lot of back tracking is supposed to do here.

A little time spent carefully performing the stated steps will be rewarded with excellent

performance.

Before proceeding in this session gather all the necessary testing instruments on the workbench.

Carefully handle the testing instruments, as they are costly electronic-gadgets to get. Know how

to operate them, before employing them in your project testing session.

Trouble-shooting the Project Kit:

First visually check for the physical disorder, improper soldering or poor connections on the PCB.


Check the mains cord, transformer output and power-supply

Check that all Components are in their proper location and are installed correctly as per the

Circuit diagram supplied with the Project Kit.


5. Application & Future Developments

APPLICATIONS:

1. The project is used to secure and avoid the road accidents.

2. It can be used as part for automation of s or Public Transportation.

3. This system is used to trace the culprit vehicles by police persons.

4. This project can also be used by Cargo Companies to intimate their on-road vehicles about

the next delivery spot or assignment.

5. This system can be used to ‘time keeping’ purpose in public transportation, such as departure

& arrival timings, number of rotations each vehicle turned etc.

Advantages:

This application is very useful on any kind of vehicle.

This application is easy to install and easy to operate.

Manpower can be saved by implementing auto detecting circuits.

More reliable than manual Operation.

Future Developments

The following modifications can be made to the present circuit, which leads to still smarter project.

Present Project can handle only two vehicles, which want to pass the one after the other, or one-by-

one. This will not happen in actual case. The two track road allows two vehicles at a time, and this

complicates the working of the Vehicle Detection Stage. One can enhance the vehicle detection

stage to detect any number of vehicles at a time. The ID of vehicles can be made more sophisticated

and secured by implementing Microcontroller/PC technology.

This system can also be used as advanced Global Posit ioning System or as an

advanced system for Automation and Vehicle Tracking.

This project can be efficiently used in ‘Vehicle Tracking & Automation’ with further improvements.

Such as, the vehicle owner can pay the ‘toll fee’ through his credit card by mentioning so in his

application form. Hence forth, whenever he come across such ‘’s, the System detects the vehicle and

charge the fee to his credit card, and allows him to pass the gate without even interrupting him. That

makes the owner to feel-free and saves his time & energy.


This project is open for developments from all sides. It is the users’ imagination which limits the

working of this project. One can go on adding the extra, rich features to this project.

BIBLIOGRAPHY

Electronic Communication Systems – George Kennedy

Electronics in Industry - George M.Chute

Principles of Electronics - V.K.Mehta

www.electronicsforu.com

www.howstuffworks.com

Telecommunication Switching, Traffic and Networks – J.E.Flood


smart zone sensing system with automatic control

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