PLEASE NOTE: THE MATTER PRODUCED BELOW IS REFERENCE MATERIAL ONLY FOR PREPARING THE PROJECT REPORT. IT IS NOT THE COMPLETE PROJECT REPORT.

1

A PROJECT REPORT ON

INDUSTRIAL BATTERY CHARGER WITH HIGH POWER

DC BY THYRISTOR FIRING ANGLE CONTROL

Submitted in partial fulfillment of the requirements

For the award of the degree

BACHELOR OF ENGINEERING

IN

____________________________________ ENGINEERING

SUBMITTED BY

-------------------- (--------------)

--------------------- (---------------)

--------------------- (---------------)

DEPARTMENT OF _______________________ ENGINEERING

__________COLLEGE OF ENGINEERING

AFFILIATED TO ___________ UNIVERSITY

2

CERTIFICATE

This is to certify that the dissertation work entitled INDUSTRIAL

BATTERY CHARGER WITH HIGH POWER DC BY THYRISTOR

FIRING ANGLE CONTROL is the work done by

_______________________________________________submitted in

partial fulfillment for the award of ‘BACHELOR OF ENGINEERING

(B.E)’in __________________________Engineering from______________

College of Engineering affiliated to _________ University , Hyderabad .

________________ ____________(Head of the department, ECE) (Assistant Professor)

EXTERNAL EXAMINER

3

ACKNOWLEDGEMENT

The satisfaction and euphoria that accompany the successful completion of any

task would be incomplete without the mentioning of the people whose constant

guidance and encouragement made it possible. We take pleasure in presenting

before you, our project, which is result of studied blend of both research and

knowledge.

We express our earnest gratitude to our internal guide, Assistant Professor

______________, Department of ECE, our project guide, for his constant support,

encouragement and guidance. We are grateful for his cooperation and his valuable

suggestions.

Finally, we express our gratitude to all other members who are involved either

directly or indirectly for the completion of this project.

4

DECLARATION

We, the undersigned, declare that the project entitled ‘INDUSTRIAL BATTERY

CHARGER WITH HIGH POWER DC BY THYRISTOR FIRING ANGLE

CONTROL’, being submitted in partial fulfillment for the award of Bachelor of

Engineering Degree in Electronics and Communication Engineering, affiliated to

_________ University, is the work carried out by us.

__________ _________ _________

__________ _________ _________

5

CONTENTS PAGE NO.

1. ABSTRACT 9

2. INTRODUCTION TO EMBEDDED SYSTEMS 10

3. BLOCK DIAGRAM 16

4. HARDWARE REQUIREMENTS 17

4.1 TRANSFORMERS 19

4.2 VOLTAGE REGULATOR (LM7805) 20

4.3 RECTIFIER 23

4.4 FILTER 24

4.5 MICROCONTROLLER (AT89S52) 24

4.6 OPTO-ISOLATOR 34

4.7 PUSH BUTTON 36

4.8 MOTOR 45

4.9 TSOP 1738 49

4.10 OPAMP (LM358)

4.11 TRIAC 50

4.12 LED 51

4.13 RESISTOR 52

4.14 CAPACITOR 53

4.15 1N4007

4.16 1N4148

5. SOFTWARE REQUIREMENTS 56

6

5.1 IDE 57

5.2 CONCEPT OF COMPILER 57

5.3 CONCEPT OF CROSS COMPILER 58

5.4 KEIL C CROSS COMPILER 59

5.5 BUILDING AN APPLICATION IN UVISION2 59

5.6 CREATING YOUR OWN APPLICATION IN UVISION2 59

5.7 DEBUGGING AN APPLICATION IN UVISION2 60

5.8 STARTING UVISION2 & CREATING A PROJECT 61

5.9 WINDOWS_ FILES 61

5.10 BUILDING PROJECTS & CREATING HEX FILES 61

5.11 CPU SIMULATION 62

5.12 DATABASE SELECTION 62

5.13 START DEBUGGING 63

5.14 DISASSEMBLY WINDOW 63

5.15 EMBEDDED C 64

6. SCHEMATIC DIAGRAM 66

5.1 DESCRIPTION 67

7. LAYOUT DIAGRAM 71

8. BILL OF MATERIAL

9. CODING 75

9.1 COMPILER 76

9.2 SOURCE CODE 84

7

10. HARDWARE TESTING 88

10.1 CONTINUITY TEST 88

10.2 POWER ON TEST 89

11. RESULTS 69

12.CONCLUSION 93

13. BIBLIOGRAPHY 94

8

LIST OF FIGURES PAGE NO.

2(a) EMBEDDED DESIGN CALLS 12

2(b) ‘V’ DIAGRAM 12

3 BLOCK DIAGRAM OF THE PROJECT 16

4.1 A TYPICAL TRANSFORMER 19

4.2(a) BLOCK DIAGRAM OF VOLTAGE REGULATOR 21

4.2(b) RATING OF VOLTAGE REGULATOR 22

4.2(c) PERFORMANCE CHARACTERISTICS

OF VOLTAGE REGULATOR 22

4.5(a) BLOCK DIAGRAM OF AT89S52 27

4.5(b) PIN DIAGRAM OF AT89S52 28

4.5(c) OSCILLATOR CONNECTIONS 32

4.2(d) EXTERNAL CLOCK DRIVE CONFIG. 33

4.2.6(b) SIGNAL FROM AN OPTOISOLATOR 42

4.2.7(a)PUSH ON BUTTON 45

4.2.7(b) TABLE TYPES OF PUSHBUTTONS 45

4.2.8 DC MOTOR 48

4.2.9(a) TSOP 1738 51

4.2.9(b) TSOP BLOCK DIAGRAM 53

4.2.10 OPAMP LM358 54

4.4 SCHEMATIC DIAGRAM 66

9

1. ABSTRACT

PLEASE REFER CD

10

2.INTRODUCTION TO EMBEDDED SYSTEMS

What is embedded system?

An Embedded System is a combination of computer hardware and software, and perhaps

additional mechanical or other parts, designed to perform a specific function. An embedded

system is a microcontroller-based, software driven, reliable, real-time control system,

autonomous, or human or network interactive, operating on diverse physical variables and in

diverse environments and sold into a competitive and cost conscious market.11

An embedded system is not a computer system that is used primarily for processing, not a

software system on PC or UNIX, not a traditional business or scientific application. High-end

embedded & lower end embedded systems. High-end embedded system - Generally 32, 64 Bit

Controllers used with OS. Examples Personal Digital Assistant and Mobile phones etc .Lower

end embedded systems - Generally 8,16 Bit Controllers used with an minimal operating systems

and hardware layout designed for the specific purpose.

SYSTEM DESIGN CALLS:

Figure 3(a): Embedded system design calls

EMBEDDED SYSTEM DESIGN CYCLE

12

EmbeddedSystems

ComputerArchitecture

SoftwareEngineering

Data Communication

ControlEngineering

Electric motorsand actuators

Sensors andmeasurements

AnalogElectronic design

DigitalElectronic design Integrated circuit

design

Embedded system design calls on many disciplines

Operating Systems

BuildDownload

DebugTools

Figuren 3(b) “V Diagram”

Characteristics of Embedded System

• An embedded system is any computer system hidden inside a product other than a

computer.

• They will encounter a number of difficulties when writing embedded system software in

addition to those we encounter when we write applications.

– Throughput – Our system may need to handle a lot of data in a short period of

time.

– Response–Our system may need to react to events quickly.

– Testability–Setting up equipment to test embedded software can be difficult.

– Debugability–Without a screen or a keyboard, finding out what the software is

doing wrong (other than not working) is a troublesome problem.

– Reliability – embedded systems must be able to handle any situation without

human intervention.

– Memory space – Memory is limited on embedded systems, and you must make

the software and the data fit into whatever memory exists.

– Program installation – you will need special tools to get your software into

embedded systems.

13

System

Testing

System

Definition

Targeting

Rapid Prototyp

ing

Hardware-in-

the-Loop Testin

g

– Power consumption – Portable systems must run on battery power, and the

software in these systems must conserve power.

– Processor hogs – computing that requires large amounts of CPU time can

complicate the response problem.

– Cost – Reducing the cost of the hardware is a concern in many embedded system

projects; software often operates on hardware that is barely adequate for the job.

• Embedded systems have a microprocessor/ microcontroller and a memory. Some have a

serial port or a network connection. They usually do not have keyboards, screens or disk

drives.

APPLICATIONS

1) Military and aerospace embedded software applications

2) Communicat ion Appl ica t ions

3) Indust r ia l automat ion and process control sof tware

4) Mastering the complexity of applications.

5) Reduction of product design time.

6) Real time processing of ever increasing amounts of data.

7) Intelligent, autonomous sensors.

CLASSIFICATION

Real Time Systems.

RTS is one which has to respond to events within a specified deadline.

A right answer after the dead line is a wrong answer.

RTS CLASSIFICATION

Hard Real Time Systems

Soft Real Time System

HARD REAL TIME SYSTEM

"Hard" real-time systems have very narrow response time.

Example: Nuclear power system, Cardiac pacemaker.

14

SOFT REAL TIME SYSTEM

"Soft" real-time systems have reduced constrains on "lateness" but still must operate very

quickly and repeatable.

Example: Railway reservation system – takes a few extra seconds the data remains valid.

3.BLOCK DIAGRAM

15

16

4.HARDWARE REQUIREMENTS

17

HARDWARE COMPONENTS:

1. TRANSFORMER (230 – 12 V AC)

2. VOLTAGE REGULATOR (LM 7805)

3. RECTIFIER

4. FILTER

5. MICROCONTROLLER (AT89S52/AT89C51)

6. OPTO-ISOLATOR

7. PUSH BUTTONS

8. MOTOR

9. TSOP 1738

10. OPAMP LM358

11. TRIAC

12. LED

13. RESISTOR

14. CAPACITOR

15. 1N4007

16.1N4148

18

4.1 TRANSFORMER

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

Step-up transformers increase voltage, step-down transformers reduce voltage. Most power

supplies use a step-down transformer to reduce the dangerously high voltage to a safer low

voltage.

FIG 4.1: A TYPICAL TRANSFORMER

The input coil is called the primary and the output coil is called the secondary. There is

no electrical connection between the two coils; instead they are linked by an alternating magnetic

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

symbol represent the core. Transformers waste very little power so the power out is (almost)

equal to the power in. Note that as voltage is stepped down and current is stepped up.

The ratio of the number of turns on each coil, called the turn’s ratio, determines the ratio

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

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

secondary (output) coil to give a low output voltage.

TURNS RATIO = (Vp / Vs) = ( Np / Ns )

Where,

Vp = primary (input) voltage.

Vs = secondary (output) voltage

Np = number of turns on primary coil

Ns = number of turns on secondary coil

Ip = primary (input) current

19

Is = secondary (output) current.

Ideal power equation

The ideal transformer as a circuit element

If the secondary coil is attached to a load that allows current to flow, electrical power is

transmitted from the primary circuit to the secondary circuit. Ideally, the transformer is perfectly

efficient; all the incoming energy is transformed from the primary circuit to the magnetic field

and into the secondary circuit. If this condition is met, the incoming electric power must equal

the outgoing power:

Giving the ideal transformer equation

Transformers normally have high efficiency, so this formula is a reasonable approximation.

If the voltage is increased, then the current is decreased by the same factor. The impedance in

one circuit is transformed by the square of the turns ratio. For example, if an impedance Zs is

20

attached across the terminals of the secondary coil, it appears to the primary circuit to have an

impedance of (Np/Ns)2Zs. This relationship is reciprocal, so that the impedance Zp of the primary

circuit appears to the secondary to be (Ns/Np)2Zp.

4.2 VOLTAGE REGULATOR 7805

Features

• Output Current up to 1A.

• Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V.

• Thermal Overload Protection.

• Short Circuit Protection.

• Output Transistor Safe Operating Area Protection.

Description

The LM78XX/LM78XXA series of three-terminal positive regulators are available in the

TO-220/D-PAK package and with several fixed output voltages, making them useful in a Wide

range of applications. Each type employs internal current limiting, thermal shutdown and safe

operating area protection, making it essentially indestructible. If adequate heat sinking is

provided, they can deliver over 1A output Current. Although designed primarily as fixed voltage 21

regulators, these devices can be used with external components to obtain adjustable voltages and

currents.

Internal Block Diagram

FIG 4.2(a): BLOCK DIAGRAM OF VOLTAGE REGULATOR

Absolute Maximum Ratings

TABLE 4.2(b): RATINGS OF THE VOLTAGE REGULATOR

22

4.3 RECTIFIER

A rectifier is an electrical device that converts alternating current (AC), which

periodically reverses direction, to direct current (DC), current that flows in only one direction, a

process known as rectification. Rectifiers have many uses including as components of power

supplies and as detectors of radio signals. Rectifiers may be made of solid state diodes, vacuum

tube diodes, mercury arc valves, and other components. The output from the transformer is fed to

the rectifier. It converts A.C. into pulsating D.C. The rectifier may be a half wave or a full wave

rectifier. In this project, a bridge rectifier is used because of its merits like good stability and full

wave rectification. In positive half cycle only two diodes( 1 set of parallel diodes) will conduct,

in negative half cycle remaining two diodes will conduct and they will conduct only in forward

bias only.

23

4.4 FILTER

Capacitive filter is used in this project. It removes the ripples from the output of rectifier

and smoothens the D.C. Output received from this filter is constant until the mains voltage and

load is maintained constant. However, if either of the two is varied, D.C. voltage received at this

point changes. Therefore a regulator is applied at the output stage.

The simple capacitor filter is the most basic type of power supply filter. The use of this

filter is very limited. It is sometimes used on extremely high-voltage, low-current power supplies

for cathode-ray and similar electron tubes that require very little load current from the supply.

This filter is also used in circuits where the power-supply ripple frequency is not critical and can

be relatively high. Below figure can show how the capacitor changes and discharges.

24

4.5 MICROCONTROLLER AT89S52

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K

bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s

high-density non volatile memory technology and is compatible with the industry standard

80C51 instruction set and pin out. The on-chip Flash allows the program memory to be

reprogrammed in-system or by a conventional non volatile memory programmer. By combining

a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel

AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective

solution to many embedded control applications. The AT89S52 provides the following standard

features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers,

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 AT89S52 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

25

system to continue functioning. The Power-down mode saves the RAM contents but freezes the

oscillator, disabling all other chip functions until the next interrupt or hardware reset.

Features:

• Compatible with MCS®-51 Products

• 8K Bytes of In-System Programmable (ISP) Flash Memory

– Endurance: 10,000 Write/Erase Cycles

• 4.0V to 5.5V Operating Range

• Fully Static Operation: 0 Hz to 33 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

• Full Duplex UART Serial Channel

• Low-power Idle and Power-down Modes

• Interrupt Recovery from Power-down Mode

• Watchdog Timer

• Dual Data Pointer

• Power-off Flag

• Fast Programming Time

• Flexible ISP Programming (Byte and Page Mode)

• Green (Pb/Halide-free) Packaging Option

Block Diagram of AT89S52:

26

FIG 4.5(A): BLOCK DIAGRAM OF AT89S52

Pin Configurations of AT89S52

27

FIG 4.5(b): PIN DIAGRAM OF AT89S52

Pin Description:

VCC:

Supply voltage.

GND:

Ground

Port 0:

Port 0 is an 8-bit open drain bidirectional 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 bytes during program

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

28

Port 1:

Port 1 is an 8-bit bidirectional 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).

Port 2:

Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers

can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled

low will 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 3:

Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers

can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled

low will source current (IIL) because of the pull-ups.

RST:

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

resets the device. This pin drives high for 98 oscillator periods after the Watchdog times out. The

DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state

of bit DISRTO, the RESET HIGH out feature is enabled.

29

ALE/PROG:

Address Latch Enable (ALE) 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.

PSEN:

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

AT89S52 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.

XTAL1:

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

XTAL2:

Output from the inverting oscillator amplifier.

Oscillator Characteristics:

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

which can be configured for use as an on-chip oscillator, as shown in Figure 1. 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 as shown in Figure 6.2. There are no

requirements on the duty cycle of the external clock signal, since the input to the internal

30

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

and low time specifications must be observed.

FIG 4.5(c): Oscillator Connections

FIG 4.5(d): External Clock Drive Configuration

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.

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.

31

4.6 OPTO-ISOLATOR (MOC3021)

A lot of electronic equipment nowadays is using optocoupler in the circuit. An

optocoupler or sometimes refer to as optoisolator allows two circuits to exchange signals yet

remain electrically isolated. This is usually accomplished by using light to relay the signal. The

standard optocoupler circuits design uses a LED shining on a phototransistor-usually it is a npn

transistor and not pnp. The signal is applied to the LED, which then shines on the transistor in

the IC.

The light is proportional to the signal, so the signal is thus transferred to the photo-

transistor. Optocouplers may also comes in few module such as the SCR, photodiodes, TRIAC

of other semiconductor switch as an output, and incandescent lamps, neon bulbs or other light

source.

In this project we have an opto-coupler MOC3021 an LED diac type combination.

Additionally while using this IC with microcontroller and one LED can be connected in series

with IC LED to indicate when high is given from micro controller such that we can know that

current is flowing in internal LED of the opto-IC. When logic high is given current flows

through LED from pin 1 to 2. So in this process LED light falls on DIAC causing 6 & 4 to close.

During each half cycle current flows through gate, series resistor and through opto-diac for the

main thyristor / triac to trigger for the load to operate.

32

The optocoupler usually found in switch mode power supply circuit in many electronic

equipment. It is connected in between the primary and secondary section of power supplies. The

optocoupler application or function in the circuit is to:

1. Monitor high voltage

2. Output voltage sampling for regulation

3. System control micro for power ON/OFF

4. Ground isolation

If the optocoupler IC breakdown, it will cause the equipment to have low power, blink, no

power, erratic power and even power shut down once switch on the equipment. Many

technicians and engineers do not know that they can actually test the optocoupler with their

analog multimeter. Most of them thought that there is no way of testing an IC with an analog

meter.

This is the principle used in Opto−Diacs, which are readily available in Integrated circuit

(I.C.) form, and do not need very complex circuitry to make them work. Simply provide a small

pulse at the right time to the Light Emitting Diode in the package. The light produced by the

LED activates the light sensitive properties of the diac and the power is switched on. The

isolation between the low power and high power circuits in these optically connected devices is

typically several thousand volts.

Pin Description:

33

4.7 PUSH BUTTONS

Fig4.7 (a): Push Buttons

A push-button (also spelled pushbutton) or simply button is a simple switch mechanism

for controlling some aspect of a machine or a process. Buttons are typically made out of hard

material, usually plastic or metal. The surface is usually flat or shaped to accommodate the

human finger or hand, so as to be easily depressed or pushed. Buttons are most often biased

switches, though even many un-biased buttons (due to their physical nature) require a spring to

return to their un-pushed state. Different people use different terms for the "pushing" of the

button, such as press, depress, mash, and punch.

Uses:

In industrial and commercial applications push buttons can be linked together by a

mechanical linkage so that the act of pushing one button causes the other button to be released.

In this way, a stop button can "force" a start button to be released. This method of linkage is used

in simple manual operations in which the machine or process have no electrical circuits for

control.

Pushbuttons are often color-coded to associate them with their function so that the

operator will not push the wrong button in error. Commonly used colors are red for stopping the

machine or process and green for starting the machine or process.

Red pushbuttons can also have large heads (mushroom shaped) for easy operation and to

facilitate the stopping of a machine. These pushbuttons are called emergency stop buttons and

are mandated by the electrical code in many jurisdictions for increased safety. This large

34

mushroom shape can also be found in buttons for use with operators who need to wear gloves for

their work and could not actuate a regular flush-mounted push button. As an aid for operators

and users in industrial or commercial applications, a pilot light is commonly added to draw the

attention of the user and to provide feedback if the button is pushed. Typically this light is

included into the center of the pushbutton and a lens replaces the pushbutton hard center disk.

The source of the energy to illuminate the light is not directly tied to the contacts on the

back of the pushbutton but to the action the pushbutton controls. In this way a start button when

pushed will cause the process or machine operation to be started and a secondary contact

designed into the operation or process will close to turn on the pilot light and signify the action

of pushing the button caused the resultant process or action to start.

In popular culture, the phrase "the button" refers to a (usually fictional) button that a

military or government leader could press to launch nuclear weapons.

Push to ON button:

Fig/4.7(b): push on button

Initially the two contacts of the button are open. When the button is pressed they become

connected. This makes the switching operation using the push button.

4.10 OPAMP LM358

General Description

The LM358 series consists of two independent, high gain; internally frequency

compensated operational amplifiers which were designed specifically to operate from a single

power supply over a wide range of voltages. Operation from split power supplies is also possible

35

and the low power supply current drain is independent of the magnitude of the power supply

voltage.

Application areas include transducer amplifiers, dc gain blocks and all the conventional

op amp circuits which now can be more easily implemented in single power supply systems. For

example, the LM358 series can be directly operated off of the standard +5V power supply

voltage which is used in digital systems and will easily provide the required interface electronics

without requiring the additional ±15V power supplies.

Unique Characteristics

In the linear mode the input common-mode voltage range includes ground and the output

voltage can also swing to ground, even though operated from only a single power supply

voltage.

The unity gain cross frequency is temperature compensated.

The input bias current is also temperature compensated.

Advantages

Two internally compensated op amps

Eliminates need for dual supplies

Allows direct sensing near GND and VOUT also goes to GND

Compatible with all forms of logic

Power drain suitable for battery operation

Features

• Available in 8-Bump micro SMD chip sized package.

• Internally frequency compensated for unity gain.

• Large dc voltage gain: 100 Db.

• Wide bandwidth (unity gain): 1 MHz (temperature compensated)

• Wide power supply range:

o Single supply: 3V to 32V

o or dual supplies: ±1.5V to ±16V

• Very low supply current drain (500 µA)-essentially independent of supply voltage.

36

• Low input offset voltage: 2 mV

• Input common-mode voltage range includes ground.

• Differential input voltage range equal to the power supply voltage.

• Large output voltage swing.

PIN CONNECTIONS

1 - Output 1

2 - Inverting input

3 - Non-inverting input

4 – VCC-

5 - Non-inverting input 2

6 - Inverting input 2

7 - Output 2

8 – VCC+

4.11 TRIAC

TRIAC, from Triode for Alternating Current, is a generalized trade name for an

electronic component which can conduct current in either direction when it is triggered (turned

on), and is formally called a bidirectional triode thyristor or bilateral triode thyristor.

A TRIAC is approximately equivalent to two complementary unilateral thyristors (one is

anode triggered and another is cathode triggered SCR) joined in inverse parallel (paralleled but

with the polarity reversed) and with their gates connected together. It can be triggered by either a

positive or a negative voltage being applied to its gate electrode (with respect to A1, otherwise

known as MT1). Once triggered, the device continues to conduct until the current through it

drops below a certain threshold value, the holding current, such as at the end of a half-cycle of

alternating current (AC) mains power. This makes the TRIAC a very convenient switch for AC 37

circuits, allowing the control of very large power flows with milliampere-scale control currents.

In addition, applying a trigger pulse at a controllable point in an AC cycle allows one to control

the percentage of current that flows through the TRIAC to the load (phase control).

TRIAC BT 136

Application

Low power TRIACs are used in many applications such as light dimmers, speed controls

for electric fans and other electric motors, and in the modern computerized control circuits of

many household small and major appliances.

However, when used with inductive loads such as electric fans, care must be taken to

assure that the TRIAC will turn off correctly at the end of each half-cycle of the AC power. A

snubber circuit (usually of the RC type) is often used between A1 and A2 to assist this turn-off.

Snubber circuits are also used to prevent premature triggering, caused for example by voltage

spikes in the mains supply. Also, a gate resistor or capacitor (or both in parallel) may be

connected between gate and A1 to further prevent false triggering. That, however, increases the

required trigger current and / or adds latency (capacitor charging).

For higher-powered, more-demanding loads, two SCRs in inverse parallel may be used

instead of one TRIAC. Because each SCR will have an entire half-cycle of reverse polarity

voltage applied to it, turn-off of the SCRs is assured, no matter what the character of the load.

However, due to the separate gates, proper triggering of the SCRs is more complex than

triggering a TRIAC.

38

In addition to commutation, a TRIAC may also not turn on reliably with non-resistive

loads if the phase shift of the current prevents achieving holding current at trigger time. To

overcome that, pulse trains may be used to repeatedly try to trigger the TRIAC until it finally

turns on. The advantage is that the gate current does not need to be maintained throughout the

entire conduction angle, which can be beneficial when there is only limited drive capability

available.

4.12 LED

LEDs are semiconductor devices. Like transistors, and other diodes, LEDs are made out

of silicon. What makes an LED give off light are the small amounts of chemical impurities that

are added to the silicon, such as gallium, arsenide, indium, and nitride.

When current passes through the LED, it emits photons as a byproduct. Normal light

bulbs produce light by heating a metal filament until its white hot. Because LEDs produce

photons directly and not via heat, they are far more efficient than incandescent bulbs.

Not long ago LEDs were only bright enough to be used as indicators on dashboards or

electronic equipment. But recent advances have made LEDs bright enough to rival traditional

lighting technologies. Modern LEDs can replace incandescent bulbs in almost any application.

LEDs are based on the semiconductor diode. When the diode is forward biased (switched

on), electrons are able to recombine with holes and energy is released in the form of light. This

effect is called electroluminescence and the color of the light is determined by the energy gap of

the semiconductor. The LED is usually small in area (less than 1 mm2) with integrated optical

components to shape its radiation pattern and assist in reflection.

39

LEDs present many advantages over traditional light sources including lower energy

consumption, longer lifetime, improved robustness, smaller size and faster switching. However,

they are relatively expensive and require more precise current and heat management than

traditional light sources.

Applications of LEDs are diverse. They are used as low-energy and also for replacements

for traditional light sources in well-established applications such as indicators and automotive

lighting. The compact size of LEDs has allowed new text and video displays and sensors to be

developed, while their high switching rates are useful in communications technology. So here the

role of LED is to indicate the status of the components like relays and power circuit etc.

4.12 RESISTORS

A resistor is a two-terminal electronic component designed to oppose an electric

current by producing a voltage drop between its terminals in proportion to the current, that is, in

accordance with Ohm's law:

V = IR

Resistors are used as part of electrical networks and electronic circuits. They are

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

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

nickel/chrome).

40

The primary characteristics of resistors are their resistance and the power they can

dissipate. Other characteristics include temperature coefficient, noise, and inductance. Less well-

known is critical resistance, the value below which power dissipation limits the maximum

permitted current flow, and above which the limit is applied voltage. Critical resistance depends

upon the materials constituting the resistor as well as its physical dimensions; it's determined by

design.

Resistors can be integrated into hybrid and printed circuits, as well as integrated

circuits. Size, and position of leads (or terminals) are relevant to equipment designers; resistors

must be physically large enough not to overheat when dissipating their power.

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

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

current I will flow through the resistor in direct proportion to that voltage. The reciprocal of the

constant of proportionality is known as the resistance R, since, with a given voltage V, a larger

value of R further "resists" the flow of current I as given by Ohm's law:

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

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

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

chrome). Resistors are also implemented within integrated circuits, particularly analog devices,

and can also be integrated into hybrid and printed circuits.

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

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

specifying that resistance in an electronic design, the required precision of the resistance may

require attention to the manufacturing tolerance of the chosen resistor, according to its specific

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

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

which must exceed the anticipated power dissipation of that resistor in a particular circuit: this is

mainly of concern in power electronics applications. Resistors with higher power ratings are

physically larger and may require heat sinking. In a high voltage circuit, attention must

sometimes be paid to the rated maximum working voltage of the resistor.41

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

this specification can be important in some high-frequency applications for smaller values of

resistance. In a low-noise amplifier or pre-amp the noise characteristics of a resistor may be an

issue. The unwanted inductance, excess noise, and temperature coefficient are mainly dependent

on the technology used in manufacturing the resistor. They are not normally specified

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

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

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

of circuits using them.

Units

The ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg Simon

Ohm. An ohm is equivalent to a volt per ampere. Since resistors are specified and manufactured

over a very large range of values, the derived units of milliohm (1 mΩ = 10−3 Ω), kilohm (1 kΩ =

103 Ω), and megohm (1 MΩ = 106 Ω) are also in common usage.

The reciprocal of resistance R is called conductance G = 1/R and is measured in Siemens

(SI unit), sometimes referred to as a mho. Thus a Siemens is the reciprocal of an ohm: S = Ω − 1.

Although the concept of conductance is often used in circuit analysis, practical resistors are

always specified in terms of their resistance (ohms) rather than conductance.

VARIABLE RESISTORS

Adjustable resistors

A resistor may have one or more fixed tapping points so that the resistance can be

changed by moving the connecting wires to different terminals. Some wire wound power

resistors have a tapping point that can slide along the resistance element, allowing a larger or

smaller part of the resistance to be used.

Where continuous adjustment of the resistance value during operation of equipment is

required, the sliding resistance tap can be connected to a knob accessible to an operator. Such a

device is called a rheostat and has two terminals.

42

Potentiometer

A potentiometer is a manually adjustable resistor. The way this device works is relatively simple.

One terminal of the potentiometer is connected to a power source. Another is hooked up to ground (a

point with no voltage or resistance and which serves as a neutral reference point), while the third

terminal runs across a strip of resistive material. This resistive strip generally has a low resistance at

one end; its resistance gradually increases to a maximum resistance at the other end. The third terminal

serves as the connection between the power source and ground, and is usually interfaced to the user by

means of a knob or lever. The user can adjust the position of the third terminal along the resistive strip

in order to manually increase or decrease resistance. By controlling resistance, a potentiometer can

determine how much current flow through a circuit. When used to regulate current, the potentiometer

is limited by the maximum resistivity of the strip.

The power of this simple device is not to be underestimated. In most analog devices, a

potentiometer is what establishes the levels of output. In a loud speaker, for example, a potentiometer

directly adjusts volume; in a television monitor, it controls brightness.

A potentiometer can also be used to control the potential difference, or voltage, across a circuit.

The setup involved in utilizing a potentiometer for this purpose is a little bit more complicated. It

involves two circuits: the first circuit consists of a cell and a resistor. At one end, the cell is connected

in series to the second circuit, and at the other end it is connected to a potentiometer in parallel with

the second circuit. The potentiometer in this arrangement drops the voltage by an amount equal to the

ratio between the resistance allowed by the position of the third terminal and the highest possible

resistivity of the strip. In other words, if the knob controlling the resistance is positioned at the exact

halfway point on the resistive strip, then the output voltage will drop by exactly fifty percent, no

43

matter how high the potentiometer's input voltage. Unlike with current regulation, voltage regulation is

not limited by the maximum resistivity of the strip

4.13 CAPACITORS

A capacitor or condenser is a passive electronic component consisting of a pair of

conductors separated by a dielectric. When a voltage potential difference exists between the

conductors, an electric field is present in the dielectric. This field stores energy and produces a

mechanical force between the plates. The effect is greatest between wide, flat, parallel, narrowly

separated conductors.

An ideal capacitor is characterized by a single constant value, capacitance, which is

measured in farads. This is the ratio of the electric charge on each conductor to the potential

difference between them. In practice, the dielectric between the plates passes a small amount of

leakage current. The conductors and leads introduce an equivalent series resistance and the

dielectric has an electric field strength limit resulting in a breakdown voltage.

The properties of capacitors in a circuit may determine the resonant frequency and

quality factor of a resonant circuit, power dissipation and operating frequency in a digital logic

circuit, energy capacity in a high-power system, and many other important aspects.

44

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

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

non-conductor. Capacitors used as parts of electrical systems, for example, consist of metal foils

separated by a layer of insulating film.

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

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

supplies, in the resonant circuits that tune radios to particular frequencies and for many other

purposes.

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

by a dielectric (insulator). When there is a potential difference (voltage) across the conductors, a

static electric field develops in the dielectric that stores energy and produces a mechanical force

between the conductors. An ideal capacitor is characterized by a single constant value,

capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the

potential difference between them.

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

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

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

current and also has an electric field strength limit, resulting in a breakdown voltage, while the

conductors and leads introduce an undesired inductance and resistance.

Theory of operation

Main article: Capacitance

45

Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric

(orange) reduces the field and increases the capacitance.

A simple demonstration of a parallel-plate capacitor

A capacitor consists of two conductors separated by a non-conductive region[8]. The non-

conductive region is called the dielectric or sometimes the dielectric medium. In simpler terms,

the dielectric is just an electrical insulator. Examples of dielectric mediums are glass, air, paper,

vacuum, and even a semiconductor depletion region chemically identical to the conductors. A

capacitor is assumed to be self-contained and isolated, with no net electric charge and no

influence from any external electric field. The conductors thus hold equal and opposite charges

on their facing surfaces,[9] and the dielectric develops an electric field. In SI units, a capacitance

of one farad means that one coulomb of charge on each conductor causes a voltage of one volt

across the device.[10]

The capacitor is a reasonably general model for electric fields within electric circuits. An ideal

capacitor is wholly characterized by a constant capacitance C, defined as the ratio of charge ±Q

on each conductor to the voltage V between them:[8]

Sometimes charge build-up affects the capacitor mechanically, causing its capacitance to vary. In

this case, capacitance is defined in terms of incremental changes:

46

Energy storage

Work must be done by an external influence to "move" charge between the conductors in a

capacitor. When the external influence is removed the charge separation persists in the electric

field and energy is stored to be released when the charge is allowed to return to its equilibrium

position. The work done in establishing the electric field, and hence the amount of energy stored,

is given by:[11]

Current-voltage relation

The current i(t) through any component in an electric circuit is defined as the rate of flow of a

charge q(t) passing through it, but actual charges, electrons, cannot pass through the dielectric

layer of a capacitor, rather an electron accumulates on the negative plate for each one that leaves

the positive plate, resulting in an electron depletion and consequent positive charge on one

electrode that is equal and opposite to the accumulated negative charge on the other. Thus the

charge on the electrodes is equal to the integral of the current as well as proportional to the

voltage as discussed above. As with any antiderivative, a constant of integration is added to

represent the initial voltage v (t0). This is the integral form of the capacitor equation,[12]

.

Taking the derivative of this, and multiplying by C, yields the derivative form,[13]

.

The dual of the capacitor is the inductor, which stores energy in the magnetic field rather than the

electric field. Its current-voltage relation is obtained by exchanging current and voltage in the

capacitor equations and replacing C with the inductance L.

DC circuits

See also: RC circuit

47

A simple resistor-capacitor circuit demonstrates charging of a capacitor.

A series circuit containing only a resistor, a capacitor, a switch and a constant DC source of

voltage V0 is known as a charging circuit.[14] If the capacitor is initially uncharged while the

switch is open, and the switch is closed at t = 0, it follows from Kirchhoff's voltage law that

Taking the derivative and multiplying by C, gives a first-order differential equation,

At t = 0, the voltage across the capacitor is zero and the voltage across the resistor is V0. The

initial current is then i (0) =V0 /R. With this assumption, the differential equation yields

where τ0 = RC is the time constant of the system.

As the capacitor reaches equilibrium with the source voltage, the voltage across the resistor and

the current through the entire circuit decay exponentially. The case of discharging a charged

capacitor likewise demonstrates exponential decay, but with the initial capacitor voltage

replacing V0 and the final voltage being zero.

AC circuits

See also: reactance (electronics) and electrical impedance#Deriving the device specific

impedances

Impedance, the vector sum of reactance and resistance, describes the phase difference and the

ratio of amplitudes between sinusoidally varying voltage and sinusoidally varying current at a

48

given frequency. Fourier analysis allows any signal to be constructed from a spectrum of

frequencies, whence the circuit's reaction to the various frequencies may be found. The reactance

and impedance of a capacitor are respectively

where j is the imaginary unit and ω is the angular velocity of the sinusoidal signal. The - j phase

indicates that the AC voltage V = Z I lags the AC current by 90°: the positive current phase

corresponds to increasing voltage as the capacitor charges; zero current corresponds to

instantaneous constant voltage, etc.

Note that impedance decreases with increasing capacitance and increasing frequency. This

implies that a higher-frequency signal or a larger capacitor results in a lower voltage amplitude

per current amplitude—an AC "short circuit" or AC coupling. Conversely, for very low

frequencies, the reactance will be high, so that a capacitor is nearly an open circuit in AC

analysis—those frequencies have been "filtered out".

Capacitors are different from resistors and inductors in that the impedance is inversely

proportional to the defining characteristic, i.e. capacitance.

Parallel plate model

Dielectric is placed between two conducting plates, each of area A and with a separation of d.

The simplest capacitor consists of two parallel conductive plates separated by a dielectric with

permittivity ε (such as air). The model may also be used to make qualitative predictions for other

device geometries. The plates are considered to extend uniformly over an area A and a charge

49

density ±ρ = ±Q/A exists on their surface. Assuming that the width of the plates is much greater

than their separation d, the electric field near the centre of the device will be uniform with the

magnitude E = ρ/ε. The voltage is defined as the line integral of the electric field between the

plates

Solving this for C = Q/V reveals that capacitance increases with area and decreases with

separation

.

The capacitance is therefore greatest in devices made from materials with a high permittivity.

Several capacitors in parallel.

Networks

See also: Series and parallel circuits

For capacitors in parallel

Capacitors in a parallel configuration each have the same applied voltage. Their

capacitances add up. Charge is apportioned among them by size. Using the schematic

diagram to visualize parallel plates, it is apparent that each capacitor contributes to the

total surface area.

For capacitors in series

50

Several capacitors in series.

Connected in series, the schematic diagram reveals that the separation distance, not the

plate area, adds up. The capacitors each store instantaneous charge build-up equal to that

of every other capacitor in the series. The total voltage difference from end to end is

apportioned to each capacitor according to the inverse of its capacitance. The entire series

acts as a capacitor smaller than any of its components.

Capacitors are combined in series to achieve a higher working voltage, for example for

smoothing a high voltage power supply. The voltage ratings, which are based on plate

separation, add up. In such an application, several series connections may in turn be

connected in parallel, forming a matrix. The goal is to maximize the energy storage utility

of each capacitor without overloading it.

Series connection is also used to adapt electrolytic capacitors for AC use.

Non-ideal behaviour

Capacitors deviate from the ideal capacitor equation in a number of ways. Some of these, such as

leakage current and parasitic effects are linear, or can be assumed to be linear, and can be dealt

with by adding virtual components to the equivalent circuit of the capacitor. The usual methods

of network analysis can then be applied. In other cases, such as with breakdown voltage, the

effect is non-linear and normal (i.e., linear) network analysis cannot be used, the effect must be

dealt with separately. There is yet another group, which may be linear but invalidate the

assumption in the analysis that capacitance is a constant. Such an example is temperature

dependence.

Breakdown voltage

Main article: Breakdown voltage

Above a particular electric field, known as the dielectric strength Eds, the dielectric in a capacitor

becomes conductive. The voltage at which this occurs is called the breakdown voltage of the

device, and is given by the product of the dielectric strength and the separation between the

conductors,[15]

Vbd = Edsd

51

The maximum energy that can be stored safely in a capacitor is limited by the breakdown

voltage. Due to the scaling of capacitance and breakdown voltage with dielectric thickness, all

capacitors made with a particular dielectric have approximately equal maximum energy density,

to the extent that the dielectric dominates their volume.[16]

For air dielectric capacitors the breakdown field strength is of the order 2 to 5 MV/m; for mica

the breakdown is 100 to 300 MV/m, for oil 15 to 25 MV/m, and can be much less when other

materials are used for the dielectric.[17] The dielectric is used in very thin layers and so absolute

breakdown voltage of capacitors is limited. Typical ratings for capacitors used for general

electronics applications range from a few volts to 100V or so. As the voltage increases, the

dielectric must be thicker, making high-voltage capacitors larger than those rated for lower

voltages. The breakdown voltage is critically affected by factors such as the geometry of the

capacitor conductive parts; sharp edges or points increase the electric field strength at that point

and can lead to a local breakdown. Once this starts to happen, the breakdown will quickly "track"

through the dielectric till it reaches the opposite plate and cause a short circuit.[18]

The usual breakdown route is that the field strength becomes large enough to pull electrons in the

dielectric from their atoms thus causing conduction. Other scenarios are possible, such as

impurities in the dielectric, and, if the dielectric is of a crystalline nature, imperfections in the

crystal structure can result in an avalanche breakdown as seen in semi-conductor devices.

Breakdown voltage is also affected by pressure, humidity and temperature.[19]

Equivalent circuit

Two different circuit models of a real capacitor

52

An ideal capacitor only stores and releases electrical energy, without dissipating any. In reality,

all capacitors have imperfections within the capacitor's material that create resistance. This is

specified as the equivalent series resistance or ESR of a component. This adds a real component

to the impedance:

As frequency approaches infinity, the capacitive impedance (or reactance) approaches zero and

the ESR becomes significant. As the reactance becomes negligible, power dissipation approaches

PRMS = VRMS² /RESR.

Similarly to ESR, the capacitor's leads add equivalent series inductance or ESL to the

component. This is usually significant only at relatively high frequencies. As inductive reactance

is positive and increases with frequency, above a certain frequency capacitance will be canceled

by inductance. High-frequency engineering involves accounting for the inductance of all

connections and components.

If the conductors are separated by a material with a small conductivity rather than a perfect

dielectric, then a small leakage current flows directly between them. The capacitor therefore has

a finite parallel resistance,[10] and slowly discharges over time (time may vary greatly depending

on the capacitor material and quality).

Ripple current

Ripple current is the AC component of an applied source (often a switched-mode power supply)

whose frequency may be constant or varying. Certain types of capacitors, such as electrolytic

tantalum capacitors, usually have a rating for maximum ripple current (both in frequency and

magnitude). This ripple current can cause damaging heat to be generated within the capacitor due

to the current flow across resistive imperfections in the materials used within the capacitor, more

commonly referred to as equivalent series resistance (ESR). For example electrolytic tantalum

capacitors are limited by ripple current and generally have the highest ESR ratings in the

capacitor family, while ceramic capacitors generally have no ripple current limitation and have

some of the lowest ESR ratings.

Capacitance instability

The capacitance of certain capacitors decreases as the component ages. In ceramic capacitors,

this is caused by degradation of the dielectric. The type of dielectric and the ambient operating 53

and storage temperatures are the most significant aging factors, while the operating voltage has a

smaller effect. The aging process may be reversed by heating the component above the Curie

point. Aging is fastest near the beginning of life of the component, and the device stabilizes over

time.[20] Electrolytic capacitors age as the electrolyte evaporates. In contrast with ceramic

capacitors, this occurs towards the end of life of the component.

Temperature dependence of capacitance is usually expressed in parts per million (ppm) per °C. It

can usually be taken as a broadly linear function but can be noticeably non-linear at the

temperature extremes. The temperature coefficient can be either positive or negative, sometimes

even amongst different samples of the same type. In other words, the spread in the range of

temperature coefficients can encompass zero. See the data sheet in the leakage current section

above for an example.

Capacitors, especially ceramic capacitors, and older designs such as paper capacitors, can absorb

sound waves resulting in a microphonic effect. Vibration moves the plates, causing the

capacitance to vary, in turn inducing AC current. Some dielectrics also generate piezoelectricity.

The resulting interference is especially problematic in audio applications, potentially causing

feedback or unintended recording. In the reverse microphonic effect, the varying electric field

between the capacitor plates exerts a physical force, moving them as a speaker. This can generate

audible sound, but drains energy and stresses the dielectric and the electrolyte, if any.

4.14 1N4007

Diodes are used to convert AC into DC these are used as half wave rectifier or full wave

rectifier. Three points must he kept in mind while using any type of diode.

1. Maximum forward current capacity

2. Maximum reverse voltage capacity

3. Maximum forward voltage capacity

54

Fig: 1N4007 diodes

The number and voltage capacity of some of the important diodes available in the market

are as follows:

Diodes of number IN4001, IN4002, IN4003, IN4004, IN4005, IN4006 and IN4007 have

maximum reverse bias voltage capacity of 50V and maximum forward current capacity of 1

Amp.

Diode of same capacities can be used in place of one another. Besides this diode of more

capacity can be used in place of diode of low capacity but diode of low capacity cannot be used

in place of diode of high capacity. For example, in place of IN4002; IN4001 or IN4007 can be

used but IN4001 or IN4002 cannot be used in place of IN4007.The diode BY125made by

company BEL is equivalent of diode from IN4001 to IN4003. BY 126 is equivalent to diodes

IN4004 to 4006 and BY 127 is equivalent to diode IN4007.

Fig:PN Junction diode

55

PN JUNCTION OPERATION

Now that you are familiar with P- and N-type materials, how these materials are joined

together to form a diode, and the function of the diode, let us continue our discussion with the

operation of the PN junction. But before we can understand how the PN junction works, we must

first consider current flow in the materials that make up the junction and what happens initially

within the junction when these two materials are joined together.

Current Flow in the N-Type Material

Conduction in the N-type semiconductor, or crystal, is similar to conduction in a copper

wire. That is, with voltage applied across the material, electrons will move through the crystal

just as current would flow in a copper wire. This is shown in figure 1-15. The positive potential

of the battery will attract the free electrons in the crystal. These electrons will leave the crystal

and flow into the positive terminal of the battery. As an electron leaves the crystal, an electron

from the negative terminal of the battery will enter the crystal, thus completing the current path.

Therefore, the majority current carriers in the N-type material (electrons) are repelled by the negative

side of the battery and move through the crystal toward the positive side of the battery.

Current Flow in the P-Type Material

Current flow through the P-type material is illustrated. Conduction in the P material is by

positive holes, instead of negative electrons. A hole moves from the positive terminal of the P

material to the negative terminal. Electrons from the external circuit enter the negative terminal

of the material and fill holes in the vicinity of this terminal. At the positive terminal, electrons

are removed from the covalent bonds, thus creating new holes. This process continues as the

steady stream of holes (hole current) moves toward the negative terminal.

56

4.15 1N4148

The 1N4148 is a standard small signal silicon diode used in signal processing. Its name

follows the JEDEC nomenclature. The 1N4148 is generally available in a DO-35 glass package

and is very useful at high frequencies with a reverse recovery time of no more than 4ns. This

permits rectification and detection of radio frequency signals very effectively, as long as their

amplitude is above the forward conduction threshold of silicon (around 0.7V) or the diode is

biased.

Specifications:

VRRM = 100V (Maximum Repetitive Reverse Voltage)

IO = 200mA (Average Rectified Forward Current)

IF = 300mA (DC Forward Current)

IFSM = 1.0 A (Pulse Width = 1 sec), 4.0 A (Pulse Width = 1 uSec) (Non-Repetitive Peak

Forward Surge Current)

PD = 500 mW (power Dissipation)

TRR < 4ns (reverse recovery time)

57

Applications

High-speed switching

Features

1) Glass sealed envelope. (GSD)

2) High speed.

3) High Reliability

Construction

Silicon epitaxial planar

58

5.SOFTWARE REQUIREMENTS

59

5.1 INTRODUCTION TO KEIL MICRO VISION (IDE)

Keil an ARM Company makes C compilers, macro assemblers, real-time kernels,

debuggers, simulators, integrated environments, evaluation boards, and emulators for

ARM7/ARM9/Cortex-M3, XC16x/C16x/ST10, 251, and 8051 MCU families.

Keil development tools for the 8051 Microcontroller Architecture support every level of

software developer from the professional applications engineer to the student just learning about

embedded software development. When starting a new project, simply select the microcontroller

you use from the Device Database and the µVision IDE sets all compiler, assembler, linker, and

memory options for you.

Keil is a cross compiler. So first we have to understand the concept of compilers and

cross compilers. After then we shall learn how to work with keil.

5.2 CONCEPT OF COMPILER

Compilers are programs used to convert a High Level Language to object code. Desktop

compilers produce an output object code for the underlying microprocessor, but not for other

microprocessors. I.E the programs written in one of the HLL like ‘C’ will compile the code to

run on the system for a particular processor like x86 (underlying microprocessor in the

computer). For example compilers for Dos platform is different from the Compilers for Unix

platform So if one wants to define a compiler then compiler is a program that translates source

code into object code.

The compiler derives its name from the way it works, looking at the entire piece of

source code and collecting and reorganizing the instruction. See there is a bit little difference

between compiler and an interpreter. Interpreter just interprets whole program at a time while

compiler analyses and execute each line of source code in succession, without looking at the

entire program.

60

The advantage of interpreters is that they can execute a program immediately. Secondly

programs produced by compilers run much faster than the same programs executed by an

interpreter. However compilers require some time before an executable program emerges. Now

as compilers translate source code into object code, which is unique for each type of computer,

many compilers are available for the same language.

5.3 CONCEPT OF CROSS COMPILER

A cross compiler is similar to the compilers but we write a program for the target

processor (like 8051 and its derivatives) on the host processors (like computer of x86). It means

being in one environment you are writing a code for another environment is called cross

development. And the compiler used for cross development is called cross compiler. So the

definition of cross compiler is a compiler that runs on one computer but produces object code for

a different type of computer.

5.4KEIL C CROSS COMPILER

Keil is a German based Software development company. It provides several

development tools like

• IDE (Integrated Development environment)

• Project Manager

• Simulator

• Debugger

• C Cross Compiler, Cross Assembler, Locator/Linker

The Keil ARM tool kit includes three main tools, assembler, compiler and linker. An

assembler is used to assemble the ARM assembly program. A compiler is used to compile the C

source code into an object file. A linker is used to create an absolute object module suitable for

our in-circuit emulator.

5.5 Building an Application in µVision2

To build (compile, assemble, and link) an application in µVision2, you must:

61

1. Select Project -(forexample,166\EXAMPLES\HELLO\HELLO.UV2).

2. Select Project - Rebuild all target files or Build target.µVision2 compiles, assembles, and

links the files in your project.

5.6 Creating Your Own Application in µVision2

To create a new project in µVision2, you must:

1. Select Project - New Project.

2. Select a directory and enter the name of the project file.

3. Select Project - Select Device and select an 8051, 251, or C16x/ST10 device from the

Device Database™.

4. Create source files to add to the project.

5. Select Project - Targets, Groups, Files. Add/Files, select Source Group1, and add the

source files to the project.

6. Select Project - Options and set the tool options. Note when you select the target device

from the Device Database™ all special options are set automatically. You typically only

need to configure the memory map of your target hardware. Default memory model

settings are optimal for most applications.

7. Select Project - Rebuild all target files or Build target.

5.7 Debugging an Application in µVision2

To debug an application created using µVision2, you must:

1. Select Debug - Start/Stop Debug Session.

2. Use the Step toolbar buttons to single-step through your program. You may enter G, main

in the Output Window to execute to the main C function.

3. Open the Serial Window using the Serial #1 button on the toolbar.

Debug your program using standard options like Step, Go, Break, and so on.

5.8 Starting µVision2 and Creating a Project

µVision2 is a standard Windows application and started by clicking on the program icon.

To create a new project file select from the µVision2 menu Project – New Project…. This opens

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a standard Windows dialog that asks you for the new project file name. We suggest that you use

a separate folder for each project. You can simply use the icon Create New Folder in this dialog

to get a new empty folder. Then select this folder and enter the file name for the new project, i.e.

Project1. µVision2 creates a new project file with the name PROJECT1.UV2 which contains a

default target and file group name. You can see these names in the Project.

5.9 Window – Files.

Now use from the menu Project – Select Device for Target and select a CPU for your

project. The Select Device dialog box shows the µVision2 device data base. Just select the

microcontroller you use. We are using for our examples the Philips 80C51RD+ CPU. This

selection sets necessary tool Options for the 80C51RD+ device and simplifies in this way the

tool Configuration.

5.10 Building Projects and Creating a HEX Files

Typical, the tool settings under Options – Target are all you need to start a new

application. You may translate all source files and line the application with a click on the Build

Target toolbar icon. When you build an application with syntax errors, µVision2 will display

errors and warning messages in the Output Window – Build page. A double click on a message

line opens the source file on the correct location in a µVision2 editor window. Once you have

successfully generated your application you can start debugging.

After you have tested your application, it is required to create an Intel HEX file to

download the software into an EPROM programmer or simulator. µVision2 creates HEX files

with each build process when Create HEX files under Options for Target – Output is enabled.

You may start your PROM programming utility after the make process when you specify the

program under the option Run User Program #1.

5.11 CPU Simulation

µVision2 simulates up to 16 Mbytes of memory from which areas can be mapped for

read, write, or code execution access. The µVision2 simulator traps

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and reports illegal memory accesses. In addition to memory mapping, the simulator also provides

support for the integrated peripherals of the various 8051 derivatives. The on-chip peripherals of

the CPU you have selected are configured from the Device.

5.12 Database selection

You have made when you create your project target. Refer to page 58 for more

Information about selecting a device. You may select and display the on-chip peripheral

components using the Debug menu. You can also change the aspects of each peripheral using the

controls in the dialog boxes.

5.13 Start Debugging

You start the debug mode of µVision2 with the Debug – Start/Stop Debug Session

Command. Depending on the Options for Target – Debug Configuration, µVision2 will load the

application program and run the startup code µVision2 saves the editor screen layout and

restores the screen layout of the last debug session. If the program execution stops, µVision2

opens an editor window with the source text or shows CPU instructions in the disassembly

window. The next executable statement is marked with a yellow arrow. During debugging, most

editor features are still available.

For example, you can use the find command or correct program errors. Program source

text of your application is shown in the same windows. The µVision2 debug mode differs from

the edit mode in the following aspects:

_ The “Debug Menu and Debug Commands” described on page 28 are available. The additional

debug windows are discussed in the following.

_ The project structure or tool parameters cannot be modified. All build commands are disabled.

5.14 Disassembly Window

The Disassembly window shows your target program as mixed source and assembly

program or just assembly code. A trace history of previously executed instructions may be 64

displayed with Debug – View Trace Records. To enable the trace history, set Debug –

Enable/Disable Trace Recording.

If you select the Disassembly Window as the active window all program step commands

work on CPU instruction level rather than program source lines. You can select a text line and

set or modify code breakpoints using toolbar buttons or the context menu commands.

You may use the dialog Debug – Inline Assembly… to modify the CPU instructions.

That allows you to correct mistakes or to make temporary changes to the target program you are

debugging. Numerous example programs are included to help you get started with the most

popular embedded 8051 devices.

The Keil µVision Debugger accurately simulates on-chip peripherals (I²C, CAN, UART,

SPI, Interrupts, I/O Ports, A/D Converter, D/A Converter, and PWM Modules) of your 8051

device. Simulation helps you understand hardware configurations and avoids time wasted on

setup problems. Additionally, with simulation, you can write and test applications before target

hardware is available.

5.15 EMBEDDED C

Use of embedded processors in passenger cars, mobile phones, medical equipment,

aerospace systems and defense systems is widespread, and even everyday domestic appliances

such as dish washers, televisions, washing machines and video recorders now include at least one

such device.

Because most embedded projects have severe cost constraints, they tend to use low-cost

processors like the 8051 family of devices considered in this book. These popular chips have

very limited resources available most such devices have around 256 bytes (not megabytes!) of

RAM, and the available processor power is around 1000 times less than that of a desktop

processor. As a result, developing embedded software presents significant new challenges, even

for experienced desktop programmers. If you have some programming experience - in C, C++

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or Java - then this book and its accompanying CD will help make your move to the embedded

world as quick and painless as possible.

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6. SCHEMATIC DIAGRAM

FOR SCHEMATIC DIAGRAM REFER TO THE CD

6.1 DESCRIPTION

POWER SUPPLY

The circuit uses standard power supply comprising of a step-down transformer from

230Vto 12V and 4 diodes forming a bridge rectifier that delivers pulsating dc which is then

filtered by an electrolytic capacitor of about 470µF to 1000µF. The filtered dc being

unregulated, IC LM7805 is used to get 5V DC constant at its pin no 3 irrespective of input DC

varying from 7V to 15V. The input dc shall be varying in the event of input ac at 230volts

section varies from 160V to 270V in the ratio of the transformer primary voltage V1 to

secondary voltage V2 governed by the formula V1/V2=N1/N2. As N1/N2 i.e. no. of turns in the

primary to the no. of turns in the secondary remains unchanged V2 is directly proportional to

V1.Thus if the transformer delivers 12V at 220V input it will give 8.72V at 160V.Similarly at

270V it will give 14.72V.Thus the dc voltage at the input of the regulator changes from about

8V to 15V because of A.C voltage variation from 160V to 270V the regulator output will remain

constant at 5V.

The regulated 5V DC is further filtered by a small electrolytic capacitor of 10µF for any

noise so generated by the circuit. One LED is connected of this 5V point in series with a current

limiting resistor of 330Ω to the ground i.e., negative voltage to indicate 5V power supply

availability. The unregulated 12V point is used for other applications as and when required.

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STANDARD CONNECTIONS TO 8051 SERIES MICRO CONTROLLER

ATMEL series of 8051 family of micro controllers need certain standard connections.

The actual number of the Microcontroller could be “89C51” , “89C52”, “89S51”, “89S52”, and

as regards to 20 pin configuration a number of “89C2051”. The 4 set of I/O ports are used based

on the project requirement. Every microcontroller requires a timing reference for its internal

program execution therefore an oscillator needs to be functional with a desired frequency to

obtain the timing reference as t =1/f.

A crystal ranging from 2 to 20 MHz is required to be used at its pin number 18 and 19 for

the internal oscillator. It may be noted here the crystal is not to be understood as crystal oscillator

It is just a crystal, while connected to the appropriate pin of the microcontroller it results in

oscillator function inside the microcontroller. Typically 11.0592 MHz crystal is used in general

for most of the circuits using 8051 series microcontroller. Two small value ceramic capacitors of

33pF each is used as a standard connection for the crystal as shown in the circuit diagram.

RESET

Pin no 9 is provided with an re-set arrangement by a combination of an electrolytic

capacitor and a register forming RC time constant. At the time of switch on, the capacitor gets

charged, and it behaves as a full short circuit from the positive to the pin number 9. After the

capacitor gets fully charged the current stops flowing and pin number 9 goes low which is pulled

down by a 10k resistor to the ground. This arrangement of reset at pin 9 going high initially and

then to logic 0 i.e., low helps the program execution to start from the beginning. In absence of

this the program execution could have taken place arbitrarily anywhere from the program cycle.

A pushbutton switch is connected across the capacitor so that at any given time as desired it can

be pressed such that it discharges the capacitor and while released the capacitor starts charging

again and then pin number 9 goes to high and then back to low, to enable the program execution

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from the beginning. This operation of high to low of the reset pin takes place in fraction of a

second as decided by the time constant R and C.

For example: A 10µF capacitor and a 10kΩ resistor would render a 100ms time to pin number 9

from logic high to low, there after the pin number 9 remains low.

External Access(EA):

Pin no 31 of 40 pin 8051 microcontroller termed as EA¯ is required to be connected to 5V for

accessing the program form the on-chip program memory. If it is connected to ground then the

controller accesses the program from external memory. However as we are using the internal

memory it is always connected to +5V.

OPTOCOUPLER

Opto coupler is a 6 pin IC. It is a combination of 1 LED and a DIAC. When the internal led light falls on the DIAC then it switches for pin no 6 and pin no 4 to get closed like a switch after exceeding the break down voltage of the diac. These devices contain a GaAs infrared emitting diode and a light activated silicon bilateral switch, which functions like a triac. They are designed for interfacing between electronic controls and power triacs to control resistive and inductive loads for 240 VAC operations.

TRIAC

A triac is said to be as an AC controlled switch. It has three terminals M1, M2 & gate. A

TRIAC, lamp load and a supply voltage are connected in series. When supply is ON at +ve cycle

then the current flows through lamp, resistors , diac, (provided a triggering pulses are provided

at pin no 1 of opto coupler resulting in pin no 4 and 6 start conducting ), gate and reaches the

supply and then only lamp glows for that half cycle directly through the M2 & M1 terminal of

the triac. In –ve half cycle the same thing repeats. Thus the lamp glows in both the cycles in a

controlled manner depending upon the triggering pulses at the opto isolator as seen on the graph

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below. If this is given to a motor instead of lamp the power is controlled resulting in speed

control.

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COMPARATOR

How an op-amp can be used as a comparator?

Potential dividers are connected to the inverting and non inverting inputs of the op-amp

to give some voltage at these terminals. Supply voltage is given to +Vss and –Vss is connected

to ground. The output of this comparator will be logic high (i.e., supply voltage) if the non-

inverting terminal input is greater than the inverting terminal input of the comparator.

i.e., Non inverting input (+) > inverting input (-) = output is logic high

If the inverting terminal input is greater than the non-inverting terminal input then the

output of the comparator will be logic low (i.e., gnd)

i.e., inverting input (-) > Non inverting input (+)

= output is logic low

ZERO VOLTAGE CROSS DETECTION USING COMPARATOR

Zero voltage cross detection means the supply voltage waveform that passes through zero

voltage for every 10msec of a 20msec cycle. We are using 50Hz ac signal, the total cycle time

period is 20msec (T=1/F=1/50=20msec) in which, for every half cycle (i.e. 10ms) we have to get

zero signals. This is achieved by using pulsating dc after the bridge rectifier before being filtered.

For that purpose we are using a blocking diode D3 between pulsating dc and the filter capacitor

so that we can get pulsating DC for use. The pulsating DC is given to potential divider of 1k

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and 4.7k to deliver an output about 5V pulsating from 12V pulsating which is connected

to non inverting input of comparator pin 3. Here Op-amp is used as comparator. The 5V DC is

given to a potential divider of 6.8K and 10k which gives an output of about 1.06V and that is

connected to inverting input pin no 2.One resistance of 1K is used from output pin 1 to input pin

2for feedback. As we know the principle of a comparator is that when non-inverting terminal is

greater than the inverting terminal then the output is logic high (supply voltage) .Thus the

pulsating dc at pin no 3 is compared with the fixed dc of 1.06V at pin no 2. The o/p of this

comparator is fed to the inverting terminal of another comparator. The non-inverting terminal of

this comparator pin no 5 is given a fixed reference voltage i.e., 2.5V taken from a voltage divider

formed from resistors of 10k and 10k. Thus we get ZVR(Zero Voltage Reference) detection.

This ZVR is then used as input pulses to microcontroller.

ZVS WAVE FORM

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OPERATION

CONNECTIONS

The output of the power supply which is 5v is connected to the 40 th pin of microcontroller

and GND is connected to 20th pin. Port 3.3 of microcontroller is connected to the pushbutton.

Port 2.0 of microcontroller is connected to the output of the comparator pin 7. Pin 2 of

MOC3021 is connected to GND.

WORKING

The project uses a zero voltage sensing circuit using LM358 OP-AMP in comparator

mode. The output of which from pin7 is given to pin1 of the microcontroller. The generation of

zero voltage reference is as explained above. This zero voltage reference is used for program

execution. Once the push button is pressed pin 21 delivers an output pulse every 10msec duration

in reference to the ZVR delayed by 1msec. Second time push delays by 2msec and the 3 rd, 4th,

5th etc., so on... This delayed pulse is given to the input of the Opto isolator through an LED to

pin 1 while pin 2 is GND. Thus the diac inside the Opto isolator MOC3021 starts conducting by

every half cycle delayed by same time as per the input at the Opto isolator. A triac BT136 is used

in series with its A1, A2 terminal, the AC 12V supply (or 230V main supply), a bridge rectifier

comprising of 4 diodes and a load resistor across the same. Therefore the DC voltage available is

based on the delayed trigger. One RC snubber is used across the A2 & A1 terminal of the triac

BT136 for taking care of dv/dt requirement its gate is triggered from the output of Opto isolator.

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7.LAYOUT DIAGRAM

Fig.7: Layout Diagram

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8. BILL OF MATERIAL

FOR BILL OF MATERIAL REFER CD

9. CODING

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9.1 COMPILER

1. Click on the Keil Vision Icon on Desktop

2. The following fig will appear

3. Click on the Project menu from the title bar

4. Then Click on New Project

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5. Save the Project by typing suitable project name with no extension in u r own folder sited in either C:\ or D:\

6. Then Click on Save button above.

7. Select the component for u r project. i.e. Atmel……

8. Click on the + Symbol beside of Atmel

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9. Select AT89C51 as shown below

10. Then Click on “OK”

11. The Following fig will appear

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12. Then Click either YES or NO………mostly “NO”.

13. Now your project is ready to USE.

14. Now double click on the Target1, you would get another option “Source group 1” as

shown in next page.

15. Click on the file option from menu bar and select “new”.80

16. The next screen will be as shown in next page, and just maximize it by double

clicking on its blue boarder.

17. Now start writing program in either in “EMBEDDED C” or “ASM”.

18. For a program written in Assembly, then save it with extension “. asm” and for

“EMBEDDED C” based program save it with extension “ .C”

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19. Now right click on Source group 1 and click on “Add files to Group Source”.

20. Now you will get another window, on which by default “EMBEDDED C” files will

appear.82

21. Now select as per your file extension given while saving the file

22. Click only one time on option “ADD”.

23. Now Press function key F7 to compile. Any error will appear if so happen.

24. If the file contains no error, then press Control+F5 simultaneously.

25. The new window is as follows

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26. Then Click “OK”.

27. Now click on the Peripherals from menu bar, and check your required port as shown

in fig below.

28. Drag the port a side and click in the program file.

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29. Now keep Pressing function key “F11” slowly and observe.

30. You are running your program successfully.

10. HARDWARE TESTING

10.1 CONTINUITY TEST:

In electronics, a continuity test is the checking of an electric circuit to see if current flows

(that it is in fact a complete circuit). A continuity test is performed by placing a small voltage

(wired in series with an LED or noise-producing component such as a piezoelectric speaker)

across the chosen path. If electron flow is inhibited by broken conductors, damaged components,

or excessive resistance, the circuit is "open".

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Devices that can be used to perform continuity tests include multi meters which measure

current and specialized continuity testers which are cheaper, more basic devices, generally with a

simple light bulb that lights up when current flows.

An important application is the continuity test of a bundle of wires so as to find the two ends

belonging to a particular one of these wires; there will be a negligible resistance between the

"right" ends, and only between the "right" ends.

This test is the performed just after the hardware soldering and configuration has been

completed. This test aims at finding any electrical open paths in the circuit after the soldering.

Many a times, the electrical continuity in the circuit is lost due to improper soldering, wrong and

rough handling of the PCB, improper usage of the soldering iron, component failures and

presence of bugs in the circuit diagram. We use a multi meter to perform this test. We keep the

multi meter in buzzer mode and connect the ground terminal of the multi meter to the ground.

We connect both the terminals across the path that needs to be checked. If there is continuation

then you will hear the beep sound.

10.2 POWER ON TEST:

This test is performed to check whether the voltage at different terminals is according to

the requirement or not. We take a multi meter and put it in voltage mode. Remember that this test

is performed without microcontroller. Firstly, we check the output of the transformer, whether

we get the required 12 v AC voltage.

Then we apply this voltage to the power supply circuit. Note that we do this test without

microcontroller because if there is any excessive voltage, this may lead to damaging the

controller. We check for the input to the voltage regulator i.e., are we getting an input of 12v and

an output of 5v. This 5v output is given to the microcontrollers’ 40 th pin. Hence we check for the

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voltage level at 40th pin. Similarly, we check for the other terminals for the required voltage. In

this way we can assure that the voltage at all the terminals is as per the requirement.

11. RESULT

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12. CONCLUSION

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13. BIBLIOGRAPHY

TEXT BOOKS REFERED

1. “The 8051 Microcontroller and Embedded systems” by Muhammad Ali Mazidi and Janice

Gillispie Mazidi , Pearson Education.

2. ATMEL 89S52 Data Sheets.

WEBSITES

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www.atmel.com

www.beyondlogic.org

www.wikipedia.org

www.howstuffworks.com

www.alldatasheets.com

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