555 - IC TIMER TESTERA Project Report

Submitted in Partial fulfillment for the award of Bachelor of Engineering in ELECTRICAL AND ELECTRONICS

Submitted to

RAJIV GANDHI PRODYOGIKI VISHWAVIDYALAYA BHOPAL (M.P)

MINOR PROJECT REPORT

Submitted By

APURV SHARMA 0103EX051009

VISHAL MODI 0103EX051059

VIVEK PODDAR 0103EX051060

Under the Supervision of

Asst.. Prof. Amol Barve

ELECTRICAL & ELECTRONICS ENGINEERING

LAKSHMI NARAIN COLLEGE OF

TECHNOLOGY, BHOPAL (M.P.)

SESSION – 2005-09

LAKSHMI NARAIN COLLEGE OF TECHNOLOGY, BHOPAL

ELECTRICAL & ELECTRONICS ENGINEERING

CERTIFICATE

This is to certify that Apurv Sharma (0103EX051009), Vishal

Modi (0103EX051059) and Vivek Poddar (0103EX051060),

have satisfactorily completed the work embodied in this

preliminary entitled “555 IC TIMER TESTER”. It is a bonafide

piece of work, carried out under our /my guidance in the

Electrical & Electronics Engineering, Lakshmi Narain

College of Technology, Bhopal for the partial fulfillment of

the Bachelor of Engineering during the academic year 2008.

Project

Guide Asst. Prof.

Manish Khemariya

Approved By

Dr. R.K Shrivastava

Head of Department

Forwarded by

Dr. Gulab Singh

Principal

Lakshmi Narain College of

Technology, Bhopal

Lakshmi Narain College of Technology, Bhopal

ELECTRICAL & ELECTRONICS ENGINEERING

DECLARATION

Apurv Sharma (0103EX051009), Vishal Modi (0103EX051059)

and Vivek Poddar (0103EX051060), students of Bachelor of

Engineering Electrical & Electronics Engineering, Lakshmi

Narain College of Technology, Bhopal. We hereby declare that

the work presented in this Minor Project is outcome of my

own work, is bonafide, correct to the best of my knowledge

and this work has been carried out taking care of

Engineering Ethics. This work does not infringe any patented

work and had not been submitted to any University for die

award of any degree or any professional diploma.

APURV SHARMA ( 0103EX051009 )

VISHAL MODI ( 0103EX051059 )

VIVEK PODDAR ( 0103EX051060 )

Date : -05-2008

CONTENTS

1. INTRODUCTION

2. COMPONENT LIST

3. DESCRIPTION OF COMPONENTS

4. OPERATING PRINCIPLE

5. CIRCUIT DIAGRAMS

6. WORKING

7. MANUFACTURING PROCESS

8. APPLICATION OF CIRCUIT

9. PRECAUTIONS

INTRODUCTION

This is a simple and easy to use gadget which not only testes the IC 555 timer in its entire basic configuration but also tests the functionally of each pin of the timer. Once a timer is declared fit by this gadget, it will function satisfactorily in whatever mode or configuration you may try it.

The circuit thus can be used to check:

(1) The timer IC in astable configuration.

(2) the timer IC in monostable configuration

(3) The capability of reset terminal to over ride all function and rest the output to low.

(4) The function of the control terminal to change the ‘on’ or ‘high’ time of output wave form in astable mode of operation and the output pulse width in monostable mode of operation.

IC 555 TIMER –

The 555 is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. The IC was designed and invented by Hans R. Camenzind. It was designed in 1970 and introduced in 1971 by Signetics (later acquired by Philips). The original name was the SE555/NE555 and was called "The IC Time Machine". It is still in wide use, thanks to its ease of use,

low price and good stability. As of 2006, 1.5 billion units are manufactured every year.

The 555 timer is one of the most popular and versatile integrated circuits ever produced. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8). The 556 is a 14-pin DIP that combines two 555s on a single chip. The 558 is a 16-pin DIP that combines four, slightly modified, 555s on a single chip (DIS & THR are connected internally; TR is falling edge sensitive instead of level sensitive). Also available are ultra-low power versions of the 555 such as the 7555 and TLC555. The 7555 requires slightly different wiring using fewer external components and less power.

The 555 has three operating modes:

Monostable mode:

in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, bouncefree switches, touch switches, Frequency Divider,Capacitance Measurement, Pulse Width Modulation (PWM) etc.

Astable mode :

Free Running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation, etc.

Bistable mode:

the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bouncefree latched switches, etc.

The connection of the pins is as follows:

1. GND Ground, low level2. TR A short pulse high → low on the trigger starts the timer3. Q During a timing interval, the output stays at +VCC4. R A timing interval can be interrupted by applying a reset pulse to low (0V)5. CV Control voltage allows access to the internal voltage divider (2/3 VCC)6. THR The threshold at which the interval ends (it ends if U.thr → 2/3 VCC)7. DIS Connected to a capacitor whose discharge time will influence the timing interval.8. V+, VCC The positive supply voltage which must be between 5 and 15 V, high level

Schematic diagram :

Real picture

COMPONENT LIST

Number Quantity

1. IC’S

IC-555 1

2. Transistors

BC548 2

3. Light emitting diodes (LED’S)

Red 1Green 1

4. Electrolytic capacitors

10F/25V 2100/25V 2

5. Ceramic capacitors

0.1 10.01 1

6. Variable resistor

Preset 1M 1

7. Carbon resistor100K 210K 21K 21M 1.33K 1.47K 1470K 1

8. Piezo element 1

10. 9V Battery 1

11. Switch 1

12. Miscellaneous

Icbase (8 pin) 2Switch connector 1Ferric chlorideSoldering wireSoldering pasteConnecting wire

DISCRIPTION OF COMPONENTS

RESISTORS -

A Resistor is a heat-dissipating element and in the

electronic circuits it is mostly used for either controlling the

current in the circuit or developing a voltage drop across it,

which could be utilized for many applications. There are various

types of resistors, which can be classified according to a

number of factors depending upon:

(I) Material used for fabrication

(II) Wattage and physical size

(III) Intended application

(IV) Ambient temperature rating

(V) Cost

Basically the resistor can be split in to the following four parts

from the construction viewpoint.

(1) Base

(2) Resistance element

(3) Terminals

(4) Protective means.

The following characteristics are inherent in all resistors and

may be controlled by design considerations and choice of

material i.e. Temperature co–efficient of resistance, Voltage co–

efficient of resistance, high frequency characteristics, power

rating, tolerance & voltage rating of resistors. Resistors may be

classified as

(1) Fixed

(2) Semi variable

(3) Variable resistor.

In our project carbon resistors are being used.

CAPACITORS:

The fundamental relation for the capacitance between two flat

plates separated by a dielectric material is given by:-

C=0.08854KA/D

Where: -

C= capacitance in pf.

K= dielectric constant

A=Area per plate in square cm.

D=Distance between two plates in cm

Design of capacitor depends on the proper dielectric

material with particular type of application. The dielectric

material used for capacitors may be grouped in various classes

like Mica, Glass, air, ceramic, paper, Aluminum, electrolyte etc.

The value of capacitance never remains constant. It changes

with temperature, frequency and aging. The capacitance value

marked on the capacitor strictly applies only at specified

temperature and at low frequencies.

LED (Light Emitting Diodes):

As its name implies it is a diode, which emits light when

forward biased. Charge carrier recombination takes place when

electrons from the N-side cross the junction and recombine with

the holes on the P side. Electrons are in the higher conduction

band on the N side whereas holes are in the lower valence band

on the P side. During recombination, some of the energy is

given up in the form of heat and light. In the case of

semiconductor materials like Gallium arsenide (GaAs), Gallium

phoshide (Gap) and Gallium arsenide phoshide (GaAsP) a

greater percentage of energy is released during recombination

and is given out in the form of light. LED emits no light when

junction is reverse biased.

TRANSISTOR: -

A transistor consists of two junctions formed by sandwiching

either p-type or n-type semiconductor between a pair of

opposite types. Accordingly, there are two types of transistors

namely: -

(1) n-p-n transistor (2) p-n-p

transistor

(NPN) (PNP)

An n-p-n transistor is composed of two n-type semiconductors

separated by a thin section of p type. However a p-n-p transistor

is formed by two p sections separated by a thin section of n-

type. In each type of transistor the following points may be

noted.

1. There are two p-n junctions, therefore a transistor may be

regarded as combination of two diodes connected back to

back.

2. There are three terminals taken from each type of

semiconductor.

3. The middle section is a very thin layer, which is the most

important factor in the functioning of a transistor.

4. Transistor can be used as an Amplifier also.

A transistor raises the strength of a weak signal and thus

acts as an amplifier. The weak signal is applied between emitter

base junction and output is taken across the load Rc connected

in the collector circuit (in common emitter configuration). In

order to achieve faithful amplification, the input circuit should

always remain forward biased.

To do so, a dc voltage is applied in the input in addition to the

signal. This dc Voltage is known as biasing voltage and its

magnitude and polarity should be such that it always keeps the

input circuit forward biased regardless of the polarity to the

signal to be amplified.

As the input circuit has low resistance a small change in

signal voltage causes an appreciable change in emitter current.

This causes change in collector current (by a factor called

current gain of transistor) due to transistor action. The collector

current flowing through a high load resistance Rc produces a

large voltage across it. Thus a weak signal applied to the input

circuit appears in the amplified form in the collector circuit.

This is how a transistor acts as an amplifier.

Transistor may be used in different configuration like CB

(common base) & CC (common collector) according to

requirements of amplifier (impedance matching, buffer

amplifier etc.).

DIODES :

- +

Diode is a two-terminal device (except that thermionic diodes

may also have one or two ancillary terminals for a heater).

consisting of a P-N junction formed either of Ge or Si crystal.

The P and N type regions are referred to as anode and cathode

respectively. Diodes have two active electrodes between which

the signal of interest may flow, and most are used for their

unidirectional current property. The varicap diode is used as an

electrically adjustable capacitor.

The directionality of current flow most diodes exhibit is

sometimes generically called the rectifying property. The most

common function of a diode is to allow an electric current to

pass in one direction (called the forward biased condition) and

to block it in the opposite direction (the reverse biased

condition). Thus, the diode can be thought of as an electronic

version of a check valve. Real diodes do not display such a

perfect on-off directionality but have a more complex non-linear

electrical characteristic, which depends on the particular type

of diode technology. Diodes also have many other functions in

which they are not designed to operate in this on-off manner.

OPERATING PRINCIPLE

The two basic configurations in which a timer ic 555 can be used are the astable and the monostable modes of operation.When the DPDT switch (s2) is in position 1-1, the timer under test automatically gets wired as a monostable multivibrator. In this case, the microswitch (S1) can trigger the monoshot. The denouncing circuit constituted by the two NAND gates of IC1 (N1 and N2) produces a clean rectangular pulse when the microswitch is pressed. Resistor R3, capacitor C1 and diode D1 ensure that the trigger terminal of timer IC 555 (pin 2 the trigger terminal) gets the desired positive to ground trigger pulse. This differentiator circuit also ensures that the width of the trigger pulse is less than expected monoshot output pulse.

The monoshot output pulse width is a function of the series combination of series combination of resistor R8 and potentiometer VR2, and capacitor C4, when DPDT switch S2 is in position 2-2, the timer gets configured for the astable mode of operation. The output is a pulse train with the high time period determine by the series combination of resistor R8, potentiometer VR2, resistor R9 and capacitor C4, whereas the low time period is determined by resistor R9 and capacitor C4.The reset terminal of timer IC (pin 4) should be tied to Vcc normally. More precisely, the voltage at the pin 4 should be greater than 0.8 volt a voltage less than resets the output .Whether you have connected the timer in the monoshot or astable mode of operation, the output goes low the moment you bring the reset terminal below 0.8V.

The control terminal (pin 5) can be used to change the high time (on time) of the output pulse train in the astable mode and the output pulse width in the monoshot mode by applying an external voltage. This external voltage basically changes the reference voltage levels of the comparator inside the IC. The level are set by three identical resistors of usually 5 kilo-ohms inside the IC connected from Vcc to ground, at 2/3Vcc for pin 5 and 1/3 Vcc for pin 2. These levels can be changed by connecting an external resistor between pin 5 and ground. Resister R10 and potentiometer VR3 have been connected for this purpose.

The pulse width in the monoshot mode is given by:

(a) 1.1*total charging resistance charging capacitance.(b) This expression is valid when three is no external

resistor connected at pin 5. The pulse width can be reduced by connecting an external resistor.

(c) The high and low time periods in the astable mode are:

High time period = 0.69*charging resistance*charging capacitanceLow time period = 0.69* charging resistance*charging capacitance.

Again the expressions sure true with no external resister at pin5. The high time period can be made to decrease by connecting an external resistor between pin 5&Gnd.

CIRCUIT DESIGN

CIRCUIT DIAGRAM OF 555 IC TESTER

PCB LAYOUT :

WORKING

To test an 555 Timer :-

1. insert into the socket

2. Set the switch S2 in position 1-1.

3. Switch on the power supply by flipping switch S3 to on position .power indicator LED (LED3) glows to indicate that the circuit is ready to test the IC TIMER.

4. If the IC is okay, LED1 glows because the IC is wired as a monoshot and in the absence of any trigger, its output is low.

5. Apply the trigger pulse by momentarily pressing switch s1 .LED1 stop glowing .This and, in turn, LED2 glows. This confirms that the output of the monoshot has gone high. After the predetermined time period, LED2 goes off and LED1 again glows .Very preset VR2 and trigger the monoshot again through switch S1. You will find that LED2 glows this time for a longer or a smaller time period depending upon whether you increased or decreased VR2 resistance.

6. For checking the reset function of the timer, trigger the monoshot again, and before the expected time is over, quickly decrease the pot meter VR1 resistance to bring the voltage at pin 4 below 0.8V .You will observe the output going low (indicated by glowing LED1 and extinguished LED2).

7. For checking the control function of the timer IC, set potmeter VR1 again in the maximum resistance position. Also set preset VR3 in the minimum position .Trigger the monoshot using switch S1 .You will observe its output going high for a time period that is much less than that determined from the series combination of R8 and VR2, and capacitor C4. In fact, for any fixed setting of this series combination, the output pulse width can be observed to very for different values of potmeter VR3 resistance –by triggering the monoshot several time, once for each setting of VR3.

8. Now set the DPDT switch in position in position 2-2 LED1 and LED2 glow alternatively with the timing determined by the resistance in charge and discharge paths. This means the timer IC is okay and wired in astable mode.

9. The function of reset and control pins can be checked in astable configuration too in the same way as discussed above for the monoshot configuration.

P.C.B. MANUFACTURING PROCESS

It is an important process in the fabrication of electronic

equipment. The design of PCBs (Printed Circuit Boards)

depends on circuit requirements like noise immunity, working

frequency and voltage levels etc. High power PCBs requires a

special design strategy.

The fabrication process to the printed circuit board will

determine to a large extent the price and reliability of the

equipment. A common target aimed is the fabrication of small

series of highly reliable professional quality PCBs with low

investment. The target becomes especially important for

customer tailored equipments in the area of industrial

electronics.

The layout of a PCB has to incorporate all the information of the

board before one can go on the artwork preparation. This

means that a concept which clearly defines all the details of the

circuit and partly defines the final equipment, is prerequisite

before the actual lay out can start. The detailed circuit diagram

is very important for the layout designer but he must also be

familiar with the design concept and with the philosophy behind

the equipment.

BOARD TYPES:

1. Single Sided Boards

The single sided PCBs are mostly used in entertainment

electronics where manufacturing costs have to be kept at a

minimum. However in industrial electronics cost factors

cannot be neglected and single sided boards should be

used wherever a particular circuit can be accommodated

on such boards.

2. Double Sided Boards

Double-sided PCBs can be made with or without plated

through holes. The production of boards with plated

through holes is fairly expensive. Therefore plated through

hole boards are only chosen where the circuit complexities

and density of components does not leave any other

choice.

CHRONOLOGY

The following steps have been followed in carrying out the

project.

1. Study the books on the relevant topic.

2. Understand the working of the circuit.

3. Prepare the circuit diagram.

4. Prepare the list of components along with their

specification.

5. Estimate the cost and procure them after carrying out

market survey.

6. Plan and prepare PCB for mounting all the components.

7. Fix the components on the PCB and solder them.

8. Test the circuit for the desired performance.

9. Trace and rectify faults if any.

10. Give good finish to the unit.

11. Prepare the project report.

DESIGN SPECIFICATION

(I) STEPS TAKEN WHILE PREPARING CIRCUIT

(A) PCB DESIGNING

The main purpose of printed circuit is in the routing of electric

currents and signal through a thin copper layer that is bounded

firmly to an insulating base material sometimes called the

substrate. This base is manufactured with an integrally bounded

layers of thin copper foil which has to be partly etched or

removed to arrive at a pre-designed pattern to suit the circuit

connections or other applications as required.

The term printed circuit board is derived from the original

method where a printed pattern is used as the mask over

wanted areas of copper. The PCB provides an ideal baseboard

upon which to assemble and hold firmly most of the small

components.

From the constructor’s point of view, the main attraction of

using PCB is its role as the mechanical support for small

components. There is less need for complicated and time

consuming metal work of chassis contraception except perhaps

in providing the final enclosure. Most straight forward circuit

designs can be easily converted in to printed wiring layer the

thought required to carry out the inversion cab footed high light

an possible error that would otherwise be missed in

conventional point to point wiring .The finished project is

usually neater and truly a work of art.

Actual size PCB layout for the circuit shown is drawn on the

copper board. The board is then immersed in FeCl3 solution for

12 hours. In this process only the exposed copper portion is

etched out by the solution.

Now the petrol washes out the paint and the copper layout on

PCB is rubbed with a smooth sand paper slowly and lightly such

that only the oxide layers over the Cu are removed. Now the

holes are drilled at the respective places according to

component layout as shown in figure.

(B) LAYOUT DESIGN:

When designing the layout one should observe the minimum

size (component body length and weight). Before starting to

design the layout we need all the required components in hand

so that an accurate assessment of space can be made. Other

space considerations might also be included from case to case

of mounted components over the printed circuit board or to

access path of present components.

It might be necessary to turn some components around to a

different angular position so that terminals are closer to the

connections of the components. The scale can be checked by

positioning the components on the squared paper. If any

connection crosses, then one can reroute to avoid such

condition.

All common or earth lines should ideally be connected to a

common line routed around the perimeter of the layout. This

will act as the ground plane. If possible try to route the outer

supply line to the ground plane. If possible try to route the other

supply lines around the opposite edge of the layout through the

center. The first set is tearing the circuit to eliminate the

crossover without altering the circuit detail in any way.

Plan the layout looking at the topside to this board. First this

should be translated inversely, later for the etching pattern

large areas are recommended to maintain good copper

adhesion. It is important to bear in mind always that copper

track width must be according to the recommended minimum

dimensions and allowance must be made for increased width

where termination holes are needed. From this aspect, it can

become little tricky to negotiate the route to connect small

transistors.

There are basically two ways of copper interconnection patterns

under side the board. The first is the removal of only the

amount of copper necessary to isolate the junctions of the

components to oneanother. The second is to make the

interconnection pattern looking more like conventional point

wiring by routing uniform width of copper from component to

component.

(C) ETCHING PROCESS:

Etching process requires the use of chemicals. acid resistant

dishes and running water supply. Ferric chloride is mostly used

solution but other etching materials such as ammonium per

sulphate can be used. Nitric acid can be used but in general it is

not used due to poisonous fumes.

The pattern prepared is glued to the copper surface of the

board using a latex type of adhesive that can be cubed after

use. The pattern is laid firmly on the copper using a very sharp

knife to cut round the pattern carefully to remove the paper

corresponding to the required copper pattern areas. Then apply

the resistant solution, which can be a kind of ink solution for the

purpose of maintaining smooth clean outlines as far as possible.

While the board is drying, test all the components.

Before going to next stage, check the whole pattern and cross

check with the circuit diagram. Check for any free metal on the

copper. The etching bath should be in a glass or enamel disc. If

using crystal of ferric- chloride these should be thoroughly

dissolved in water to the proportion suggested. There should be

0.5 lt. of water for 125 gm of crystal.

To prevent particles of copper hindering further etching, agitate

the solutions carefully by gently twisting or rocking the tray.

The board should not be left in the bath a moment longer than

is needed to remove just the right amount of copper. Inspite of

there being a resistive coating there is no protection against

etching away through exposed copper edges. This leads to over

etching. Have running water ready so that etched board can be

removed properly and rinsed. This will halt etching

immediately.

Drilling is one of those operations that calls for great care. For

most purposes a 0.5mm drill is used. Drill all holes with this size

first those that need to be larger can be easily drilled again with

the appropriate larger size.

(D) COMPONENT ASSEMBLY: -

From the greatest variety of electronic components available,

which runs into thousands of different types it is often a

perplexing task to know which is right for a given job.

There could be damage such as hairline crack on PCB. If there

are, then they can be repaired by soldering a short link of bare

copper wire over the affected part.

The most popular method of holding all the items is to bring the

wires far apart after they have been inserted in the appropriate

holes. This will hold the component in position ready for

soldering.

Some components will be considerably larger .So it is best to

start mounting the smallest first and progressing through to the

largest. Before starting, be certain that no further drilling is

likely to be necessary because access may be impossible later.

Next will probably be the resistor, small signal diodes or other

similar size components. Some capacitors are also very small

but it would be best to fit these afterwards. When fitting each

group of components mark off each one on the circuit as it is

fitted so that if we have to leave the job we know where to

recommence.

Although transistors and integrated circuits are small items

there are good reasons for leaving the soldering of these until

the last step. The main point is that these components are very

sensitive to heat and if subjected to prolonged application of the

soldering iron, they could be internally damaged.

All the components before mounting are rubbed with sand

paper so that oxide layer is removed from the tips. Now they

are mounted according to the component layout.

(E) SOLDERING: -

This is the operation of joining the components with PCB after

this operation the circuit will be ready to use to avoid any

damage or fault during this operation following care must be

taken.

1. A longer duration contact between soldering iron bit &

components lead can exceed the temperature rating of device &

cause partial or total damage of the device. Hence before

soldering we must carefully read the maximum soldering

temperature & soldering time for device.

2. The wattage of soldering iron should be selected as minimum

as permissible for that soldering place.

3 .To protect the devices by leakage current of iron its bit

should be earthed properly.

4. We should select the soldering wire with proper ratio of Pb &

Tn to provide the suitable melting temperature.

5. Proper amount of good quality flux must be applied on the

soldering point to avoid dry soldering.

APPLICATION OF CIRCUIT

The circuit thus can be used to check:

a. The timer IC in astable configuration.

b. The timer IC in monostable configuration

c. The capability of reset terminal to override all function and rest the output to low.

d. The function of the control terminal to change the ‘on’ or ‘high’ time of output wave form in astable mode of operation and the output pulse width in monostable mode of operation.

This operates on a 9v battery which makes the gadget portable you can construct easily on any general purpose PCB along with the 8 pin socket.

PRECAUTIONS :

1. The soldering iron being used for soldering of semiconductors should be of low voltage.

2. While soldering semiconductors heat sinks should be used.

3. While soldering solder should not spread over the entire circuit and solder tip should be sharp and smooth.

4. While mounting components their values should be visible.

5. Semiconductors and other polarized components should be mounted with correct polarity.

6. Time should be carefully observed while etching process takes place on the PCB.