power saving street light

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www.final-yearproject.com | www.finalyearthesis.com

B.TECH PROJECT REPORT

ON

POWER SAVING STREET LIGHT Submitted to

Uttar Pradesh Technical University

in partial fulfillment of the requirement for award ofthedegree

Of

BACHELOR OF TECHNOLOGYIn

ELECTRONICS & COMMUNICATION

To:-Mr. Vijay Kumar

BY:-MAYANK RASTOGI

(0831131405)

PUNIT KUMAR (0831131406)

PUNIT SHARMA

(0831131407)

RAHUL KUMAR

(0831131408)
http://www.final-yearproject.com/http://www.finalyearthesis.com/http://www.final-yearproject.com/http://www.finalyearthesis.com/


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NITIN KANT (0831131000)

CERTIFICATE

To whom it may concern

This is to certify that the work which is being presented in the project report

titled POWER SAVING STREET LIGHT in partial fulfillment for the

award of the degree of B.Tech and submitted to the department of

Electronics and Telecommunication Engineering, COER, is an authenticrecord of the work carried out by MAYANK RASTOGI,PUNIT KUMAR,PUNIT

SHARMA, RAHUL KUMAR,NITIN KANT , during the academic session 2011-

2012. The matter presented in this report has not been submitted by the

candidates for the award of any other degree.

Mr. Vijay Kumar

(HOD& Project Coordinator).

E.C. Deptt.


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ACKNOWLEDGEMENT

We are grateful to Dr. Priyanka, Sr. Lecturer, Electronics &

Telecommunication Department, College of Engineering Roorkee for

her constant encouragement and guidance during the preparation of

this work.

We express our sincere gratitude to Mr. B.D.Patel, HoD, Electronics &

Telecommunication Department, College of Engineering Roorkee, for

his invaluable suggestions and constructive criticism regarding this

report.

Last but not the least, we are thankful to all those who helped us in

any way to prepare this report.

Mayank RastogiPunit Kumar

Punit SharmaRahul Kumar

Nitin Kant


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MEANING OF PROJECT

The project gives the significance of the following field of engineering-

P- Signifies the phenomenon of planning which deals with symbolic nationand proper arrangement of sense and suggestion receptivity accordingly tothe needs.

R- It is associate with the word resources which guides to promote planning.

OJ-This letters signifies the overhead expenses in un estimated expensesthat may occur in the manufacture design or layout of the project.

E- Signifies the word engineering.

C- Signifies the convey about phenomenon of construction low cost.

T- The word T stands for the word technique unless there is technique; it isimpossible to complete the project.


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TABLE OF CONTENTS

1. INTRODUCTION 1-3

1.1. PLATFORM USED

1.2. AIM OF THE PROJECT

2. BLOCK DIAGRAM 4-82.1. WORKING OF THE PROJECT

2.2. CIRCUIT DIAGRAM

2.3. DESCRIPTION

3. PCB LAYOUT 10-13

3.1. STEPS FOR MAKING PCB

3.2. PROGRAMMING

4. SENSING UNIT DESCRIPTION 14-38

4.1. MICROCONTROLLER UNIT

4.2. COMPONENTS DESCRIPTION

5. CONCLUSION71

5.1REFERENCE


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5.2.WEBSITE

1. INTRODUCTION

POWER SAVING STREET LIGHT is an embedded project. And we are

presenting in this project how the power could be saved using power saving

street light which automatically gets off in day time and gets on in night .It

also sense moving vehicles and people travelling on road and gets on at that

time.

Since automation is the need of hour, technology is enhancing and hence wehavedesigned a system for electricity saving of the street lights on the highway.This system shows the advancement in technology as well as it also savesthe energy.Embedded is the combination of both hardware and software. Hardware in

this field is electronics hardware where as the software is the programming

of the microcontroller.


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Microcontroller is the decision making device, it works on two logic 0 and 1.Microcontroller is similar to the microprocessor but the basic difference

between two is the inbuilt memory in the controller which make it a cheap IC

costs about Rs 50 where as the cost of the processor is about Rs 400.

This heart of this project is ATMEL microcontroller and the controlleravailable in the market has to be used so we have used 89C2051, 20 pin

controller according to the requirement.

Since automation is the need of hour, technology is enhancing and hence wehavedesigned a system for electricity saving of the street lights on the highway.This system shows the advancement in technology as well as it also savesthe energy.

1.1.PLATFORM USED

SOFTWARE REQUIREMENTS1. Batronix Prog Studio for programming of Microcontroller

2. Orcad for Circuit Designing

3. Pads for PCB designing

HARDWARE REQUIREMENTS


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1. Microcontroller 89c2051

2. Crystal Oscillator

3. Resistors

4. Capacitors

5. Connectors

6. Diode

7. White Led

8. Yellow light

9. Pressure sensors

10. Led Reflectors

11. Light Dependent Resistance

1.2. AIM OF THE PROJECT


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The aim of the project is to design such system through which we can save the electricity of the

street light on the highways using the microcontroller.

This project presenting the working of the power saving street light which make itself

turn on and off as per requirement. Different sensors has been used here for sensing

whether any vehicle is on the track or not, or any person is on pedestrian or

not ,by making use of microcontroller it automatically turn on and off the street light.

2. BLOCK DIAGRAM: Figure below shows the block diagram of

Power SavingStreet Light.

BLOCK DIAGRAM:


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Fig. 4.1 Fig. 2.1

2.1. WORKING OF THE PROJECT

MICROCONTROLLER

POWER SUPPLY

VEHICLE

STREET

LIGHT

LDR

LIGHT


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Now as our objective is to save the electricity we have used LDRs to sense the light. There are

three LDRs used in our project, two for detection of light from the vehicle as soon as the vehicle

comes near to the street light poles the corresponding Led will glow and also there is an LDR forsensing the Day and night mode if it is daytime then the LEDs will remain off.

Now the question arises what about the pedestrian so there are pressure sensor switches which

will get press as soon as any passerby passes through the road.

2.2. CIRCUIT DIAGRAM


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Fig.2.2.1 project diagram

Attach the hard copy of the ckt diagram

Component list

Attach hard copy of component list2.3. CIRCUIT DESCRIPTION

POWER SUPPLY SECTION:

POWER SUPPLY


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The ac voltage 120v rms is connected to a transformer which steps that ac

voltage down to the level for the desired dc output. A diode rectifier then

provides a full wave rectified voltage that is initially filtered by a simple

capacitor filter to produce a dc voltage. This resulting dc voltage has some

ripple or ac voltage variation. A regulator circuit can use this dc input to

provide a dc voltage that not only has much less ripple voltage but also

remains the same dc value even if the input dc voltage varies somewhat or

the load connected to the output dc voltage changes.

The output voltage of a filter circuit has dc level and the rms value of the

output voltage.

RIPPLE = [ripple voltage(rms)] / [dc voltage]

= (Vr(rms)/Vdc

Diagram of power supply:

Fig. 2.3.1

Consists of:

1. RLMT Connector--- It is a connector used to connect the step downtransformer to the bridge rectifier.


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2. Bridge Rectifier --- It is a full wave rectifier used to convert ac intodc , 9-15v ac made by transformer is converted into dc with the help ofrectifier.

3. Capacitor: -----It is an electrolytic capacitor of rating 1000M/35Vused to remove the ripples. Capacitor is the component used to passthe ac and block the dc.

4. Regulator: ----LM7805 is used to give a fixed 5v regulated supply.

5. Capacitor: -----It is again an electrolytic capacitor 10M/65v used forfiltering to give pure dc.

6. Capacitor: ----- It is a ceramic capacitor used to remove the spikesgenerated when frequency is high (spikes).

So the output of supply section is 5v regulated dc.

MICROCONTROLLER SECTION:


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Requires three connections to be successfully done for its operation to

begin.

1. +5v supply: This +5v supply is required for the controller to get startwhich is provided from the power supply section. This supply is provided atpin no.31and 40 of the 89c2051 controller.

2. Crystal Oscillator: A crystal oscillator of 12 MHz is connected at pinno.19,x1 and pin no.18,x2 to generate the frequency for the controller.The crystal oscillator works on piezoelectric effect. The clock generated isused to determine the processing speed of the controller. Two capacitors

are also connected one end with the oscillator while the other end isconnected with the ground. As it is recommended in the book to connecttwo ceramic capacitor of 20 pf40pf to stabilize the clock generated.

3. Reset section: It consists of an RC network consisting of 10M/35Vcapacitor and one resistance of 1k. This section is used to reset thecontroller connected at pin no.9 of AT89c51.


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3.PCB LAYOUTAttach the hard copy of the component layout

Attach the hard copy of the pcb layout


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3.1. STEPS FOR MAKING PCB

Prepare the layout of the circuit (positive).

Cut the photo film (slightly bigger) of the size of the layout.

Place the layout in the photo printer machine with the photo film above it.Make sure that the bromide (dark) side of the film is in contact with thelayout.

Switch on the machine by pressing the push button for 5 sec.

Dip the film in the solution prepared (developer) by mixing the chemicals A& B in equal quantities in water.

Now clean the film by placing it in the tray containing water for 1 min.

After this, dip the film in the fixer solution for 1 min. now the negative ofthe

Circuit is ready.

Now wash it under the flowing water.

Dry the negative in the photo cure machine.

Take the PCB board of the size of the layout and clean it with steel wool tomake the surface smooth.

Now dip the PCB in the liquid photo resist, with the help of dip coat

machine.

Now clip the PCB next to the negative in the photo cure machine, drying forapproximate 10-12 minute.

Now place the negative on the top of the PCB in the UV machine, set thetimer for about 2.5 minute and switch on the UV light at the top.


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Take the LPR developer in a container and rigorously move the PCB in it.

After this, wash it with water very gently.

Then apply LPR dye on it with the help of a dropper so that it is completelycovered by it.

Now clamp the PCB in the etching machine that contains ferric chloridesolution for about 10 minutes.

After etching, wash the PCB with water, wipe it a dry cloth softly.

Finally rub the PCB with a steel wool, and the PCB is ready.

3.2.Programming

Attach hard copy programming


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4. SENSING UNITDESCRIPTION

LDR


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In this circuit we are using a LDR sensor for providing command to fire alarm system this

system is interfaced to the alarm section and water pump section of the test area whenever it

sense a hazardous condition a particular pin of Microcontroller become high or low accordingly

this signal is sensed by our microcontroller according to the signal sensed microcontroller of

alarm system generate signal for Alarm Section and water pump. Photo resistor

Fig. 4.1

A light dependent resistor

Fig. 4.2

The internal components of a photoelectric control for a typical American streetlight. The

photoresistor is facing rightwards, and controls whether current flows through the heater which

opens the main power contacts. At night, the heater cools, closing the power contacts, energizing

the street light. The heater/bimetal mechanism provides a built-in time-delay.
http://en.wikipedia.org/wiki/Streetlighthttp://en.wikipedia.org/wiki/File:Streetlight_control.jpghttp://en.wikipedia.org/wiki/File:LDR.jpghttp://en.wikipedia.org/wiki/File:LDR.jpghttp://en.wikipedia.org/wiki/Streetlight


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A photoresistor orlight dependent resistor orcadmium sulfide (CdS) cell is a resistorwhose

resistance decreases with increasing incident light intensity. It can also be referenced as a

photoconductor.

A photoresistor is made of a high resistance semiconductor. If light falling on the device is of

high enough frequency, photons absorbed by the semiconductor give bound electrons enough

energy to jump into the conduction band. The resulting free electron (and its hole partner)

conduct electricity, thereby lowering resistance.

A photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor has its own

charge carriers and is not an efficient semiconductor, e.g. silicon. In intrinsic devices the only

available electrons are in the valence band, and hence the photon must have enough energy to

excite the electron across the entire bandgap. Extrinsic devices have impurities, also called

dopants, added whose ground state energy is closer to the conduction band; since the electrons

do not have as far to jump, lower energy photons (i.e., longer wavelengths and lower

frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms

replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction.

This is an example of an extrinsic semiconductor.

Applications

Photoresistors come in many different types. Inexpensive cadmium sulfide cells can be found in

many consumer items such as camera light meters, street lights, clock radios, alarms, and

outdoor clocks.

They are also used in some dynamic compressors together with a small incandescent lamp or

light emitting diode to control gain reduction.
http://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Bandgaphttp://en.wikipedia.org/wiki/Dopantshttp://en.wikipedia.org/wiki/Cadmium_sulfidehttp://en.wikipedia.org/wiki/Alarmhttp://en.wikipedia.org/wiki/Dynamic_range_compressionhttp://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Bandgaphttp://en.wikipedia.org/wiki/Dopantshttp://en.wikipedia.org/wiki/Cadmium_sulfidehttp://en.wikipedia.org/wiki/Alarmhttp://en.wikipedia.org/wiki/Dynamic_range_compression


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Lead sulfide and indium antimonide LDRs are used for the mid infrared spectral region. Ge:Cu

photoconductors are among the best far-infrared detectors available, and are used for infrared

astronomy and infrared spectroscopy.

Circuit symbol

Below is a symbol for a photoresistor as used in some circuit diagrams.

Fig. 4.3

4.1.MICROCONTROLLER UNIT

Microcontroller AT89C2051

Features

Compatible with MCS-51 Products
http://en.wikipedia.org/wiki/Lead_sulfidehttp://en.wikipedia.org/wiki/Indium_antimonidehttp://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Infrared_astronomyhttp://en.wikipedia.org/wiki/Infrared_astronomyhttp://en.wikipedia.org/wiki/Infrared_spectroscopyhttp://en.wikipedia.org/wiki/File:Light-dependent_resistor_schematic_symbol.svghttp://en.wikipedia.org/wiki/Lead_sulfidehttp://en.wikipedia.org/wiki/Indium_antimonidehttp://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Infrared_astronomyhttp://en.wikipedia.org/wiki/Infrared_astronomyhttp://en.wikipedia.org/wiki/Infrared_spectroscopy


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2K Bytes of Re programmable Flash Memory

Endurance: 1,000 Write/Erase Cycles

2.7V to 6V Operating Range

Fully Static Operation: 0 Hz to 24 MHz

Two-level Program Memory Lock

128 x 8-bit Internal RAM

15 Programmable I/O Lines

Two16-bit Timer/Counters

Six Interrupt Source

Programmable Serial UART Channel

Direct LED Drive Outputs

On-chip Analog Comparator

Low-power Idle and Power-down Modes

Description

TheAT89C2051 is low-voltage; high-performance CMOS 8-bit microcomputer with2K bytes of

Flash programmable and erasable read only memory (PEROM). The device is manufactured

using Atmels high-density nonvolatile memory technology and is compatible with the industry-

standard MCS-51 instruction set. By combining versatile 8-bit CPU with Flash on a monolithic

chip, the Atmel AT89C2051 is a powerful microcomputer, which provides a highly flexible and

cost-effective solution to many embedded control applications.

The AT89C2051 provides the following standard features: 2K bytes of Flash, 128bytes of RAM,

15 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full

duplex serial port, a precision analog comparator, on-chip oscillator and clock circuitry. In

addition, the AT89C2051 is designed with static logic for operation down to zero frequency and

supports two software selectable power saving modes. The Idle Mode stops the CPU while

allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The

power-down mode saves the RAM contents but freezes the oscillator disabling all other chip

functions until the next hardware reset.

Pin Configuration


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Fig. 4.1.1 Pin Description

VCC: Supply voltage

GND: Ground

Port 1:

Port 1 is an 8-bit bi-directional I/O port. Port pins P1.2 toP1.7 provides internal pull-ups. P1.0

and P1.1 require external pull-ups. P1.0 and P1.1 also serve as the positive input (AIN0) and the

negative input (AIN1), respectively, of the on-chip precision analog comparator. The Port 1

output buffers can sink 20 m A and can drive LED displays directly. When 1s are written to Port

1 pins, they can be used as inputs. When pins P1.2 to P1.7 are used as inputs and are externally


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pulled low, they will source current (IIL) because of the internal pull-ups. Port 1 also receives

code data during Flash programming and verification.

Port 3:

Port 3 pins P3.0 to P3.5, P3.7 are seven bi-directional I/O pins with internal pull-ups. P3.6 is

hard-wired as an input to the output of the on-chip comparator and is not accessible as a general

purpose I/O pin. The Port 3 output buffers can sink 20 MA. 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.

Port 3 also serves the functions of various special features of theAT89C2051 as listed below:

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

RST:

Reset input. All I/O pins are reset to 1s as soon as RST goes high. Holding the RST pin high for

two machine cycles while the oscillator is running resets the device.

Each machine cycle takes 12 oscillator or clock cycles.

XTAL1:


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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 2.

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

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

voltage high and low time specifications must be observed.

Figure 1:Oscillator Connections

Fig.4.1.2

Note: C1, C2 = 30 PF 10 PF for Crystals


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= 40 PF 10 PF for Ceramic Resonators

Figure 2. External Clock Drive Configuration

Fig. 4.1.3

AT89C2051 4

Special Function Registers

A map of the on-chip memory area called the Special Function Register SFR) pace is shown inthe table below.

Note that not all of the addresses are occupied and unoccupied addresses ay not be implemented

on the chip. Read accesses to these addresses will in general return random data, and write

accesses will have an indeterminate

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

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

will always be 0

Table 1:AT89C2051 SFR Map and Reset Values


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.

Fig. 4.1.4

Restrictions on Certain Instructions:

The AT89C2051 and is an economical and cost-effective member of Atmels growing family of

micro controllers .It contains 2K bytes of flash program memory. It is fully compatible with the

MCS-51 architecture, and can be programmed using the MCS-51 instruction set. However there

are a few considerations one must keep in mind when utilizing certain instructions to program

this device.All the instructions related to jumping or branching should be restricted such that the destination

address falls within the physical program memory space of the device, which is2K for the

AT89C205 This should be her responsibility of the software programmer. For example, LJMP

7E0Hwould be a valid instruction for the AT89C2051 (with 2K of memory) , whereas JMP

900H would not.


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Branching instructions

LCALL, LJMP, ACALL, AJMP, SJMP, JMP @A+DPTR

These unconditional branching instructions will execute correctly as long as the programmer

keeps in mind that the destination branching address must fall within the physical boundaries of

the program memory size (locations 00H to7FFH for the 89C2051). Violating the physical space

limits

May cause unknown program behavior.

CJNE [...], DJNZ [...], JB, JNB, JC, JNC, JBC, JZ, JNZ With

These conditional branching instructions the same rule above applies. Again, violating the

memory boundaries may cause erratic execution .For applications involving interrupts the

normal interrupt service routine address locations of the 80C51 family architecture have been

preserved.

MOVX-related instructions, Data Memory

The AT89C2051 contains 128 bytes of internal data memory. Thus, in the T89C2051 the stack

depth is limited to128 bytes, the amount of available RAM. External DATA memory access is

not supported in this device, nor is external PROGRAM memory execution. Therefore, no

MOVX [...] instructions should be included in the program.

A typical 80C51 assembler will still assemble instructions, even if they are written in violation of

the restrictions mentioned above. It is the responsibility of the controller user to know the

physical features and limitations of the device being used and adjust the instructions used

correspondingly.

Program Memory Lock Bits


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On the chip are two lock bits which can be left un programmed (U) or can be programmed (P) to

obtain the additional features listed in the table below:

Lock Bit Protection Modes (1)

Note: 1 The Lock Bits can only be erased with the Chip Erase operation.

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.

P1.0 and P1.1 should be set to 0 if no external pull ups are used, or set to 1 if external pull

ups are used. It should be noted that when idle is terminated by a hardware reset, the devicenormally resumes program execution, from where it left off, up to two machine cycles before the

internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this

event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected

write to a port pin when Idle is


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Terminated by reset, the instruction following the one that invokes Idle should not be one that

writes to a port pin or to external memory.

Power-down Mode

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

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

values until the power down mode is

Terminated. The only exit from power down is a hard ware reset. Reset redefines the SFR s 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.

P1.0 and P1.1 should be set to 0 if no external pull-ups are used, or set to 1 if external pull-

ups are used.

Programming The Flash

The AT89C2051 is shipped with the 2K bytes of on-chip PEROM code memory array in the

erased state (i.e., contents= FFH) and ready to be programmed. The code

Memory array is programmed one byte at a time. Once the array is programmed, to re-

program any non-blank byte the entire memory array needs to be erased electrically.

Internal Address Counter:The AT89C2051 contains an internal PEROM address counter, which

is always reset to000H on the rising edge of RST and is advanced by applying a positive going

pulse to pin XTAL1.

Programming Algorithm:To program the AT89C2051,the following sequence is recommended.

1. Power-up sequence:

Apply power between VCC and GND pins Set RST and XTAL1 to GND

2. Set pin RST to H


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Set pin P3.2 to H

3. Apply the appropriate combination of H or L logic levels to pins P3.3, P3.4, P3.5, P3.7 to

select one of the programming operations shown in the PEROM Programming Modes table.

To Program and Verify the Array:

4. Apply data for Code byte at location 000H to P1.0 to

P1.7.

5. Raise RST to 12V to enable programming.

6. Pulse P3.2 once to program a byte in the PEROM array or the lock bits. The byte-write cycle

is self-timed and typically takes 1.2 ms.

7. To verify the programmed data, lower RST from 12V to logic H level and set pins P3.3 to

P3.7 to the appropriate levels. Output data can be read at the port P1 pins.

8. To program a byte at the next address location, pulseXTAL1 pin once to advance the internal

address

9. Repeat steps 5 through 8, changing data and advancing the counter. Apply new data to the port

P1 pins. Address counter for the entire 2K bytes array or until the end of the object file is

reached.

10. Power-off sequence:

Set XTAL1 to L

Set RST to L

Turn VCC power off

Data Polling: The AT89C2051 features Data Polling to indicate the end of a write cycle.

During a write cycle, an attempted read of the last byte written will result in the complement of

the written data on P1.7. Once the write cycle has been completed, true data is valid on all

outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has

been initiated.

Ready/Busy: The Progress of byte programming can also be monitored by the RDY/BSY

output signal. Pin P3.1 is pulled low after P3.2 goes High during programming to indicate

BUSY. P3.1 is pulled High again when programming is done to indicate READY.


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Program Verify: If lock bits LB1 and LB2 have not been programmed code data can be read

back via the data lines for verification:

1. Reset the internal address counter to 000H by bringing RST from L to H.

2. Apply the appropriate control signals for Read Code data and read the output data at the port

P1 pins.

3. Pulse pin XTAL1 once to advance the internal address counter.

4. Read the next code data byte at the port P1 pins.

5. Repeat steps 3 and 4 until the entire array is read .The lock bits cannot be verified directly.

Verification of the lock bits is achieved by observing that their features are enabled.

Chip Erase: The entire PEROM array (2K bytes) and the two Lock Bits are erased electrically

by using the proper combination of control signals and by holding P3.2 low for 10 ms. The code

array is written with all 1s in the Chip.

Erase operation and must be executed before any nonblank memory byte can be re-programmed.

Reading the Signature Bytes: The signature bytes are read by the same procedure as a normal

verification of locations 000H, 001H, and 002H, except that P3.5 and P3.7 must be pulled to

logic low. The values returned are as follows.

(000H) = 1EH indicates manufactured by Atmel

(001H) = 21H indicates 89C2051

Programming Interface:

Every code byte in the Flash array can be written and using the appropriate combination of

control signals can erase the entire array. The write operation cycle is self timed and once

initiated, will automatically time itself to completion.

All major programming vendors offer worldwide support for the Atmel micro controller series.

Please contact your local programming vendor for the appropriate software revision.

Flash Programming Modes


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Fig. 4.1.5

Notes: 1. The internal PEROM address counter is reset to 000H on the rising edge of RST and is

advanced by a positive pulse at XTAL 1 pin.

2. Chip Erase requires a 10 ms PROG pulse.

3. P3.1 is pulled Low during programming to indicate RDY/BS

Figure 3. Programming the Flash Memory

Figure 4. Verifying the Flash Memory

Fig.4.1.6

Flash Programming and Verification Characteristics


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Fig. 4.1.7

Flash Programming and Verification Waveforms


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Fig.4.1.8

Fig.4.1.8


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Fig.4.1.9

Serial Port Timing: Shift Register Mode Test Conditions

Shift Register Mode Timing Waveforms

Fig.4.1.10


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Fig.4.1.11


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Fig.4.1.12

Pressure Sensor/Switch

A pressure sensor or switch measures pressure. Pressure is usually expressed in terms of force

per unit area. A pressure sensor usually acts as a transducer; it generates a signal as a function of


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the pressure imposed. Fig.4.1.13

Pressure sensors can be classified in term of pressure ranges they measure, temperature ranges

of operation, and most importantly the type of pressure they measure. In terms of pressure type,

pressure sensors can be divided into five categories:

1) Absolute pressure sensor

This sensor measures the pressure relative to perfect vacuum pressure.

2) Gauge pressure sensor

This sensor is used in different applications because it can be calibrated to measure the pressure

relative to a given atmospheric pressure at a given location.

3) Vacuum pressure sensor

This sensor is used to measure pressure less than the atmospheric pressure at a given location.

4) Differential pressure sensor

This sensor measures the difference between two or more pressures introduced as inputs to the

sensing unit.

5) Sealed pressure sensor

This sensor is the same as the gauge pressure sensor except that it is previously calibrated by

manufacturers to measure pressure relative to sea level pressure.


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Fig:4.1.14 Operation of pressure switch

1.10.1 Pressure Sensing Technology

There are two basic categories of analog pressure sensors:

(i) Force collector types - These types of electronic pressure sensors generally use a force

collector (such a diaphragm, piston, bourdon tube, or bellows) to measure strain (or deflection)

due to applied force (pressure) over an area.

(ii) Other types - These types of electronic pressure sensors use other properties (such as

density) to infer pressure of a gas, or liquid.

Here well discuss only about Force collector type of pressure sensors. Force collecting pressure

sensors are of following types:

Piezoresistive Strain Gauge-

Uses the piezoresistive effect of bonded or formed strain gauges to detect strain due to applied

pressure. Generally, the strain gauges are connected to form a wheat stone bridge circuit tomaximize the output of the sensor. This is the most commonly employed sensing technology for

general purpose pressure measurement.

Capacitive - Uses a diaphragm and pressure cavity to create a variable capacitor to detect strain

due to applied pressure. Common technologies use metal, ceramic, and silicon diaphragms.


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Generally, these technologies are most applied to low pressures (Absolute, Differential and

Gauge)

Electromagnetic - Measures the displacement of a diaphragm by means of changes in

inductance (reluctance), LVDT, Hall Effect, or by eddy current principal.

Piezoelectric - Uses the piezoelectric effect in certain materials such as quartz to measure the

strain upon the sensing mechanism due to pressure. This technology is commonly employed for

the measurement of highly dynamic pressures.

Optical - Uses the physical change of an optical fiber to detect strain due to applied pressure.

Potentiometric - Uses the motion of a wiper along a resistive mechanism to detect the strain

caused by applied pressure .


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4.2.COMPONENTS DESCRIPTION

TRANSFORMER:

A transformer is a static device by means of which electric power in one circuit is transformed

into electric power of the same frequency .In another circuit. It can lower the voltage in the

circuit but with a corresponding decreases or increase in current. The physical basis of

transformer is mutual induction between two circuit linked by a magnetic field. In its simplest

form, it consists of two inductive coils, which are electrically separated but magnetically linked

through a path of low reluctance as shown in fig. The two coils are connected to a source of

alternating voltage. An alternating flux is set up in the laminated core. Most of which is linked

with the other coil in which it produces mutually induced e-m-f of the second coil c-k-t is closed,

a current flows in it and so electric energy is transformed from the first coil to the second coil

.The first coil in which electric energy is fed from the ac main supply, is called primary winding

and the other from which energy is drown, out is called secondary winding. In bried a

transformer is a device.

1. Transfer electric power from one ckt to another.

2. It does so without a change of forge.

3. It accomplishes this by electromagnetic inductive influence of each other

Transformer losses:

Transformer losses are produced by the electrical current flowing in the coils and the magnetic

field alternating in the core. The losses associated with the coils are called the load losses, while

the losses produced in the core are called no-load losses.


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WHAT ARE LOAD LOSSES?

Load losses vary according to the loading on the transformer. They include heat losses and eddy

currents in the primary and secondary conductors of the transformer.

Heat losses, or I2R losses, in the winding materials contribute the largest part of the load losses.

They are created by resistance of the conductor to the flow of current or electrons. The electron

motion causes the conductor molecules to move and produce friction and heat. The energy

generated by this motion can be calculated using the formula:

Watts = (volts)(amperes) or VI.

According to Ohms law, V=RI, or the voltage drop across a resistor equals the amount of

resistance in the resistor, R, multiplied by the current, I, flowing in the resistor. Hence, heat

losses equal (I) (RI) or I2R.

Transformer designers cannot change I, or the current portion of the I2R losses, which are

determined by the load requirements. They can only change the resistance or R part of the I2R by

using a material that has a low resistance per cross-sectional area without adding significantly to

the cost of the transformer. Most transformer designers have found copper the best conductor

considering the weight, size, cost and resistance of the conductor. Designers can also reduce the

resistance of the conductor by increasing the cross-sectional area of the conductor.

WHAT ARE NO-LOAD LOSSES?

No-load losses are caused by the magnetizing current needed to energize the core of the

transformer, and do not vary according to the loading on the transformer. They are constant and


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occur 24 hours a day, 365 days a year, regardless of the load, hence the term no-load losses.

They can be categorized into five components: hysteresis losses in the core laminations, eddy

current losses in the core laminations, I2R losses due to no-load current, stray eddy current losses

in core clamps, bolts and other core components, and dielectric losses. Hysteresis losses and

eddy current losses contribute over 99% of the no-load losses, while stray eddy current, dielectric

losses and I2R losses due to no-load current are small and consequently often neglected. Thinner

lamination of the core steel reduces eddy current losses.

The biggest contributor to no-load losses is hysteresis losses. Hysteresis losses come from the

molecules in the core laminations resisting being magnetized and demagnetized by the

alternating magnetic field. This resistance by the molecules causes friction that results in heat.

The Greek word, hysteresis, means "to lag" and refers to the fact that the magnetic flux lags

behind the magnetic force. Choice of size and type of core material reduces hysteresis losses

BRIDGE RECTIFIER

A diode bridge or bridge rectifier is an arrangement of four diodes connected in a bridge

circuit as shown below, that provides the same polarity of output voltage for any polarity of the

input voltage. When used in its most common application, for conversion of alternating current

(AC) input into direct current (DC) output, it is known as a bridge rectifier. The bridge recitifier

provides full wave rectification from a two wire AC input (saving the cost of a center tapped

transformer) but has two diode drops rather than one reducing efficiency over a center tap based

design for the same output voltage.


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Diodes; the one on the left is a diode bridge Fig.4.2.1

Fig.4.2.2

Schematic of a diode bridge:

VOLTAGE REGULATION

Another factor of importance in a power supply is the amount the dc output voltage changes

over a range of ckt operation. The voltage provided at the output under no load condition is

reduced when load current is drawn from the supply. The amount the dc voltage changes

between the no load and load condition is described by the voltage regulation

VOLTAGE REGULATION= [no-load voltage-full loadvoltage]/[full loadvoltage]
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VOLTAGE REGULATORS:

A Voltage Regulator (also called a "regulator") has only three legs and appears to be a

comparatively simple device but it is actually a very complex integrated circuit. A regulator

converts varying input voltage and produces a constant "regulated" output voltage. Voltage

regulators are available in a variety of outputs, typically 5 volts, 9 volts and 12 volts. The last

two digits in the name indicate the output voltage.

Name Voltage

LM7805 + 5 volts

LM7809 + 9 volts

LM7812 + 12 volts

LM7905 - 5 volts

LM7909 - 9 volts

LM7912 - 12 volts


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LM7805 Integrated Circuit Internal Schematic

Fig.4.2.3

The "LM78XX" series of voltage regulators are designed for positive input. For applications

requiring negative input the "LM79XX" series is used.


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Symbol for a Voltage Regulator.

This device looks like a Transistor,

but it is actually a complex

Integrated Circuit.

A LM7805 Regulator

Fig.4.2.4

IC VOLTAGE REGULATOR

Regulator IC units contain the circuitry for reference source, comparator amplifiers, control

device, and overload protection all in a single IC. IC units provides regulation of either a fixed

positive voltage , affixed negative voltage or an adjustably set voltage.

THREE TERMINAL VOLTAGE REGULATORS

The basic connection of a three terminal voltage regulator IC to a load. The fixed voltage

regulator has an unregulated dc input voltage vi, applied to one input terminal, a regulated dc

output voltage ,from a second terminal, with the third terminal connected to the ground. for a

selected regulator ,ICdevice specifications list a voltage range over which the input voltage can

vary to maintain a regulated output voltage over a range of load current. He specification also

list the amount of output voltage changes resulting from a change in load current or in input

voltage.


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The series 78 regulators provides fixed regulated voltage from 5 to 24v. IC 7805 is connected to

provide voltage regulation with output from this is +5V DC. AN UNREGULATED INPUT

VTG IS filtered by capacitor c1 and connected to the ICs IN terminal. The ICS

out terminal provides a regulated +5v which is filtered by a capacitor c2. The third terminal

connected to the ground.

CAPACITOR FILTER

A very popular filter circuit is the capacitor filter is connected at the rectifier output and a dc

voltage is obtained across the capacitor.

Vdc=vm-(Idc/4fc)

Where vm is the peak rectifier voltage, Idc is the load current in milliampand cis the filter

capacitor in microfarads.

ACTIVE COMPONENT-

Active component are those component for not any other component are used its operation. I

used in this project only function diode, these component description are described as bellow.

DIODE

SEMICONDUCTOR DIODE-

A PN junctions is known as a semiconductor or crystal diode.A crystal diode has two

terminal when it is connected in a circuit one thing is decide is weather a diode is forward or


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reversed biased. There is a easy rule to ascertain it. If the external CKT is trying to push the

conventional current in the direction of error, the diode is forward biased. One the other hand if

the conventional current is trying is trying to flow opposite the error head, the diode is reversed

biased putting in simple words.

Fig.4.2.5

1. If arrowhead of diode symbol is positive W.R.T Bar of the symbol, the diode is

forward biased.

2. The arrowhead of diode symbol is negative W.R.T bar, the diode is the reverse bias.

When we used crystal diode it is often necessary to know that which end is arrowhead

and which end is bar. So following method are available.

1. Some manufactures actually point the symbol on the body of the diode e. g By127 by

11 4 crystal diode manufacture by b e b.

Fig.4.2.6


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2. Sometimes red and blue marks are on the body of the crystal diode. Red mark do not

arrow wheres blue mark indicates bar e .g oa80 crystal diode.

ZENER DIODE-

It has been already discussed that when the reverse bias on a crystal diode is

increased a critical voltage, called break down voltage. The break down or zener voltage depends

upon the amount of doping. If the diode is heavily doped depletion layer will be thin and

consequently the break down of he junction will occur at a lower reverse voltage. On the other

hand, a lightly doped diode has a higher break down voltage, it is called zener diode

.

.

Fig.4.2.7

A properly doped crystal diode, which has a shaped break down voltage, is known as a zenor

diode.


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Crystal Oscillator

It is often required to produce a signal whose frequency or pulse rate is very stable and exactly

known. This is important in any application where anything to do with time or exact

measurement is

crucial. It is relatively simple to make an oscillator that produces some sort of a signal, but

another matter to produce one of relatively precise frequency and stability. AM radio stations

must have a carrier frequency accurate within 10Hz of its assigned frequency, which may be

from 530 to 1710 kHz. SSB radio systems used in the HF range (2-30 MHz) must be within 50

Hz of channel frequency for acceptable voice quality, and within 10 Hz for best results. Some

digital modes used in weak signal communication may require frequency stability of less than 1

Hz within a period of several minutes. The carrier frequency must be known to fractions of a

hertz in some cases. An ordinary quartz watch must have an oscillator accurate to better than a

few parts per million. One part per million will result in an error of slightly less than one half

second a day, which would be about 3 minutes a year. This might not sound like much, but an

error of 10 parts per million would result in an error of about a half an hour per year. A clock

such as this would need resetting about once a month, and more often if you are the punctual

type. A programmed VCR with a clock this far off could miss the recording of part of a TV

show. Narrow band SSB communications at VHF and UHF frequencies still need 50 Hz

frequency accuracy. At 440 MHz, this is slightly more than 0.1 part per million.

Ordinary L-C oscillators using conventional inductors and capacitors can achieve typically 0.01

to 0.1 percent frequency stability, about 100 to 1000 Hz at 1 MHz. This is OK for AM and FM

broadcast receiver applications and in other low-end analog receivers not requiring high tuning

accuracy. By careful design and component selection, and with rugged mechanical

construction, .01 to 0.001%, or even better (.0005%) stability can be achieved. The better figures

will undoubtedly employ temperature compensation components and regulated power supplies,


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together with environmental control (good ventilation and ambient temperature regulation) and

battleship mechanical construction. This has been done in some communications receivers

used by the military and commercial HF communication receivers built in the 1950-1965 era,

before the widespread use of digital frequency synthesis. But these receivers were extremely

expensive, large, and heavy. Many modern consumer grade AM, FM, and shortwave receivers

employing crystal controlled digital frequency synthesis will do as well or better from a

frequency stability standpoint.

An oscillator is basically an amplifier and a frequency selective feedback network (Fig 1). When,

at a particular frequency, the loop gain is unity or more, and the total phaseshift at this frequency

is zero, or some multiple of 360 degrees, the condition for oscillation is satisfied, and the circuit

will produce a periodic waveform of this frequency. This is usually a sine wave, or square wave,

but triangles, impulses, or other waveforms can be produced. In fact, several different waveforms

often are simultaneously produced by the same circuit, at different points. It is also possible to

have several frequencies produced as well, although this is generally undesirable.

Transistors

Fig.4.2.8


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A transistor is a semiconductor device used to amplify and switch electronic signals. It is made

of a solid piece of semiconductor material, with at least three terminals for connection to an

external circuit. A voltage or current applied to one pair of the transistor's terminals changes the

current flowing through another pair of terminals. Because the controlled (output)power can be

much more than the controlling (input) power, the transistor provides amplification of a signal.

Some transistors are packaged individually but many more are found embedded in integrated

circuits.

The transistor is the fundamental building block of modern electronic devices, and its presence is

ubiquitous in modern electronic systems.

A bipolar (junction) transistor(BJT) is a three-terminal electronic device constructed ofdoped

semiconductormaterial and may be used in amplifying or switching

applications. Bipolar transistors are so named because their operation involves

bothelectrons and holes. Charge flow in a BJT is due to bidirectional diffusion of charge carriers

across a junction between two regions of different charge concentrations. This mode of operation

is contrasted with unipolar transistors, such asfield-effect transistors, in which only one carrier

type is involved in charge flow due todrift. By design, most of the BJT collector current is due

to the flow of charges injected from a high-concentration emitter into the base where they

are minority carriers that diffuse toward the collector, and so BJTs are classified as minority-

carrier devices.

A bipolar transistor has terminals labeled base, collector, and emitter. A small current at the base

terminal (that is, flowing from the base to the emitter) can control or switch a much larger

current between the collector and emitter terminals.

Fig.4.2.9
http://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Doping_(Semiconductors)http://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Field-effect_transistorhttp://en.wikipedia.org/wiki/Field-effect_transistorhttp://en.wikipedia.org/wiki/Drift_velocityhttp://en.wikipedia.org/wiki/Drift_velocityhttp://en.wikipedia.org/wiki/Drift_velocityhttp://en.wikipedia.org/wiki/Minority_carrierhttp://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Doping_(Semiconductors)http://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Field-effect_transistorhttp://en.wikipedia.org/wiki/Drift_velocityhttp://en.wikipedia.org/wiki/Minority_carrier


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Types of BJT

1) NPN

Fig.4.2. 10

NPN is one of the two types of bipolar transistors, in which the letters "N" and "P" refer to the

majority charge carriers inside the different regions of the transistor. Most bipolar transistors

used today are NPN, because electron mobility is higher than hole mobility in semiconductors,

allowing greater currents and faster operation.

NPN transistors consist of a layer of P-doped semiconductor (the "base") between two N-doped

layers. A small current entering the base in common-emitter mode is amplified in the collector

output. In other terms, an NPN transistor is "on" when its base is pulled high relative to the

emitter.

The arrow in the NPN transistor symbol is on the emitter leg and points in the direction of the

conventional current flow when the device is in forward active mode.

2) PNP

The other type of BJT is the PNP with the letters "P" and "N" referring to the majority charge

carriers inside the different regions of the transistor.

Fig.4.2.10


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PNP transistors consist of a layer of N-doped semiconductor between two layers of P-doped

material. A small current leaving the base in common-emitter mode is amplified in the collector

output. In other terms, a PNP transistor is "on" when its base is pulled low relative to the emitter.

The arrow in the PNP transistor symbol is on the emitter leg and points in the direction of

the conventional current flow when the device is in forward active mode.

Active mode of Transistors


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(i) Active-mode NPN transistors in circuits

Fig.4.2.11

The diagram above is a schematic representation of an NPN transistor connected to two voltage

sources. To make the transistor conduct appreciable current (on the order of 1 mA) from C to

E, VBE must be above a minimum value sometimes referred to as the cut-in voltage. The cut-in

voltage is usually about 600 mV for silicon BJTs at room temperature but can be different

depending on the type of transistor and its biasing. This applied voltage causes the lower P-N

junction to 'turn-on' allowing a flow of electrons from the emitter into the base. In active mode,

the electric field existing between base and collector (caused by VCE) will cause the majority of

these electrons to cross the upper P-N junction into the collector to form the collector currentIC.

The remainder of the electrons recombine with holes, the majority carriers in the base, making a

current through the base connection to form the base current, IB. As shown in the diagram, the

emitter current,IE, is the total transistor current, which is the sum of the other terminal currents

(i.e. ).In the diagram, the arrows representing current point in the direction of conventional current

the flow of electrons is in the opposite direction of the arrows because electrons carry

negative electric charge. In active mode, the ratio of the collector current to the base current is

called theDC current gain. This gain is usually 100 or more, but robust circuit designs do not

depend on the exact value (for example see op-amp). The value of this gain for DC signals is

referred to as hFE, and the value of this gain for AC signals is referred to as hfe. However, when

there is no particular frequency range of interest, the symbol is used

It should also be noted that the emitter current is related to VBE exponentially. At room

temperature, an increase in VBE by approximately 60 mV increases the emitter current by a factor

of 10. Because the base current is approximately proportional to the collector and emitter

currents, they vary in the same way.


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(ii) Active-mode PNP transistors in circuits

Fig.4.2.12

The diagram shown is a schematic representation of a PNP transistor connected to two voltage

sources. To make the transistor conduct appreciable current (on the order of 1 mA) from E to

C, VEB must be above a minimum value sometimes referred to as the cut-in voltage. The cut-in

voltage is usually about 600 mV for silicon BJTs at room temperature but can be different

depending on the type of transistor and its biasing. This applied voltage causes the upper P-N

junction to 'turn-on' allowing a flow of holes from the emitter into the base. In active mode, the

electric field existing between the emitter and the collector (caused by VCE) causes the majority

of these holes to cross the lower P-N junction into the collector to form the collector currentIC.

The remainder of the holes recombine with electrons, the majority carriers in the base, making a

current through the base connection to form the base current, IB. As shown in the diagram, the

emitter current,IE, is the total transistor current, which is the sum of the other terminal currents(i.e., ).

In the diagram, the arrows representing current point in the direction of conventional current

the flow of holes is in the same direction of the arrows because holes carry positive electric

charge. In active mode, the ratio of the collector current to the base current is called theDC

current gain. This gain is usually 100 or more, but robust circuit designs do not depend on the

exact value. The value of this gain for DC signals is referred to as hFE, and the value of this gain

for AC signals is referred to as hfe. However, when there is no particular frequency range of

interest, the symbol is used

It should also be noted that the emitter current is related to VEB exponentially. At room

temperature, an increase in VEB by approximately 60 mV increases the emitter current by a factor

of 10. Because the base current is approximately proportional to the collector and emitter

currents, they vary in the same way.


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Transistor as a switch

Fig.4.2.13

.

Transistors are commonly used as electronic switches, for both high power applications

including switched-mode power supplies and low power applications such as logic gates.


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In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base

voltage rises the base and collector current rise exponentially, and the collector voltage drops

because of the collector load resistor. The relevant equations:

VRC = ICE RC, the voltage across the load (the lamp with resistance RC)

VRC + VCE = VCC, the supply voltage shown as 6V

If VCE could fall to 0 (perfect closed switch) then Ic could go no higher than VCC / RC, even with

higher base voltage and current. The transistor is then said to be saturated. Hence, values of input

voltage can be chosen such that the output is either completely off or completely on. The

transistor is acting as a switch, and this type of operation is common in digital circuits where

only "on" and "off" values are relevant.

CAPACITOR

A capacitor orcondenser is a passiveelectronic component consisting of a pair ofconductors

separated by a dielectric (insulator). When a potential difference (voltage) exists across the

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

mechanical force between the conductors. The effect is greatest when there is a narrow

separation between large areas of conductor, hence capacitor conductors are often called plates.

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.

Capacitors are widely used in electronic circuits to block the flow of direct current while

allowing alternating current to pass, to filter out interference, to smooth the output ofpower

supplies, and for many other purposes. They are used in resonant circuits in radio frequency

equipment to select particularfrequencies from a signal with many frequencies.
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Fig.4.2.14

Theory of operation

Main article: Capacitance

Fig. 4.2.15

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

(orange) reduces the field and increases the capacitance.
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Fig.4.2.16

A simple demonstration of a parallel-plate capacitor

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

conductive substance is called the dielectric medium, although this may also mean a vacuum or a

semiconductordepletion 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 an external

electric field. The conductors thus contain equal and opposite charges on their facing surfaces,

and the dielectric contains an electric field. 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 Vbetween them

Sometimes charge buildup affects the mechanics of the capacitor, causing the capacitance to

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

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.

Energy storage

Work must be done by an external influence to move charge between the conductors in acapacitor. When the external influence is removed, the charge separation persists and energy is

stored in the electric field. If charge is later allowed to return to its equilibriumposition, the

energy is released. The work done in establishing the electric field, and hence the amount of

energy stored, is given by:
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Current-voltage relation

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

charge q(t) that has passed through it. Physical charges cannot pass through the dielectric layer of

a capacitor, but rather build up in equal and opposite quantities on the electrodes: as each

electron accumulates on the negative plate, one leaves the positive plate. Thus the accumulated

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

.

Taking the derivative of this, and multiplying by C, yields the derivative form,[12]

.

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 Cwith the inductanceL.

DC circuits

Fig.4.2.17
http://en.wikipedia.org/wiki/Antiderivativehttp://en.wikipedia.org/wiki/Constant_of_integrationhttp://en.wikipedia.org/wiki/Capacitor#cite_note-Dorf_p260-11http://en.wikipedia.org/wiki/Duality_(electrical_circuits)http://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/File:RC_switch.svghttp://en.wikipedia.org/wiki/Antiderivativehttp://en.wikipedia.org/wiki/Constant_of_integrationhttp://en.wikipedia.org/wiki/Capacitor#cite_note-Dorf_p260-11http://en.wikipedia.org/wiki/Duality_(electrical_circuits)http://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Magnetic_field


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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. 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 0 =RCis the time constantof 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 ofdischarging a charged

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

replacing V0 and the final voltage being zero.

RESISTOR
http://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/Kirchhoff's_voltage_lawhttp://en.wikipedia.org/wiki/First-order_differential_equationhttp://en.wikipedia.org/wiki/Time_constanthttp://en.wikipedia.org/wiki/Time_constanthttp://en.wikipedia.org/wiki/Exponential_decayhttp://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/Kirchhoff's_voltage_lawhttp://en.wikipedia.org/wiki/First-order_differential_equationhttp://en.wikipedia.org/wiki/Time_constanthttp://en.wikipedia.org/wiki/Exponential_decay


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Resistors are used to limit the value of current in a circuit. Resistors offer

opposition to the flow of current. They are expressed in ohms for which the

symbol is . Resistors are broadly classified as

(1)Fixed Resistors

(2)Variable Resistors

Fixed Resistors:

The most common of low wattage, fixed type resistors is the molded-carbon

composition resistor. The resistive material is of carbon clay composition.

The leads are made of tinned copper. Resistors of this type are readily

available in value ranging from few ohms to about 20M, having a tolerance

range of 5 to 20%. They are quite inexpensive. The relative size of all fixed

resistors changes with the wattage rating.

Another variety of carbon composition resistors is the metalized type. It is made

by deposition a homogeneous film of pure carbon over a glass, ceramic or other insulating core.This type of film-resistor is sometimes called the precision type, since it can be obtained with an

accuracy of 1%.

Lead Tinned Copper Material

Colour Coding Molded Carbon Clay Composition

Fig.4.2.18Fixed Resistor

A Wire Wound Resistor :

It uses a length of resistance wire, such as nichrome. This wire is woundedon to a round hollow porcelain core. The ends of the winding are attached to

these metal pieces inserted in the core. Tinned copper wire leads are

attached to these metal pieces. This assembly is coated with an enamel

coating powdered glass. This coating is very smooth and gives mechanical

protection to winding. Commonly available wire wound resistors have


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resistance values ranging from 1 to 100K, and wattage rating up to about

200W.

Coding Of Resistor:

Some resistors are large enough in size to have their resistance printed on

the body. However there are some resistors that are too small in size to have

numbers printed on them. Therefore, a system of colour coding is used to

indicate their values. For fixed, moulded composition resistor four colour

bands are printed on one end of the outer casing. The colour bands are

always read left to right from the end that has the bands closest to it. The

first and second band represents the first and second significant digits, of the

resistance value. The third band is for the number of zeros that follow the

second digit. In case the third band is gold or silver, it represents amultiplying factor of 0.1to 0.01. The fourth band represents the

manufactures tolerance.


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RESISTOR COLOUR CHART

Fig.4.2.19

For example, if a resistor has a colour band sequence: yellow, violet,orange and gold

Then its range will be

Yellow=4, violet=7, orange=10, gold=5% =47K 5% =2.35K

Most resistors have 4 bands:

The first band gives the first digit. The second band gives the second digit. The third band indicates the number of zeros. The fourth band is used to show the tolerance (precision) of the

resistor.

5 green

0 black

1 brown

2 red

3 orange

4 yellow

6 blue

7 purple

8 silver

9 white

0 black

1 brown

2 red

3 orange

4 yellow

6 blue

7 purple

8 silver

9 white

5green

5 green

0 black

1 brown

2 red

3 orange

4 yellow

6 blue

7 purple

8 silver

9 white

5 green

0 black

1 brown

2 red

3 orange

4 yellow

6 blue

7 purple

8 silver

9 white


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Fig.4.2.20

This resistor has red (2), violet (7), yellow (4 zeros) and gold bands.

So its value is 270000 = 270 k .

The standard colour code cannot show values of less than 10 . To show

these small values two special colours are used for the third band: gold,

which means 0.1 and silver which means 0.01. The first and second

bands represent the digits as normal.

For example:

red, violet, gold bands represent 27 0.1 = 2.7

blue, green, silverbands represent 56 0.01 = 0.56

The fourth band of the colour code shows the tolerance of a resistor.

Tolerance is the precision of the resistor and it is given as a percentage. For

example a 390 resistor with a tolerance of 10% will have a value within

10% of 390 , between 390 - 39 = 351 and 390 + 39 = 429 (39 is 10% of

390).

A special colour code is used for the fourth band tolerance:

silver 10%, gold 5%, red 2%, brown 1%.If no fourth band is shown the tolerance is 20%.

VARIABLE RESISTOR: In electronic circuits, sometimes it becomes

necessary to adjust the values of currents and voltages. For n example it is

often desired to change the volume of sound, the brightness of a televisionpicture etc. Such adjustments can be done by using variable resistors.

Although the variable resistors are usually called rheostats in otherapplications, the smaller variable resistors commonly used in electronic circuitsare called potentiometers.


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Resistor shorthand:

Resistor values are often written on circuit diagrams using a code system

which avoids using a decimal point because it is easy to miss the small dot.

Instead the letters R, K and M are used in place of the decimal point. To read

the code: replace the letter with a decimal point, then multiply the value by

1000 if the letter was K, or 1000000 if the letter was M. The letter R means

multiply by 1.

For example:

560R means 560

2K7 means 2.7 k = 2700

39K means 39 k

1M0 means 1.0 M = 1000 k

Power Ratings of Resistors

Fig.4.2.21

Electrical energy is converted to heat when current flows through a resistor. Usually the

effect is negligible, but if the resistance is low (or the voltage across the resistor high) a

large current may pass making the resistor become noticeably warm. The resistor must be

able to withstand the heating effect and resistors have power ratings to show this.

Power ratings of resistors are rarely quoted in parts lists because for most circuits the standard

power ratings of 0.25W or 0.5W are suitable. For the rare cases where a higher power is required

High power resistors

(5W top, 25W bottom)

Photographs Rapid Electronics
http://www.rapidelectronics.co.uk/http://www.rapidelectronics.co.uk/http://www.rapidelectronics.co.uk/


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it should be clearly specified in the parts list, these will be circuits using low value resistors (less

than about 300 ) or high voltages (more than 15V).

The power, P, developed in a resistor is given by:

P = I R

or

P = V / R

where: P = power developed in the resistor in watts (W)

I = current through the resistor in amps (A)

R = resistance of the resistor in ohms ( )

V = voltage across the resistor in volts (V)

Examples:

A 470 resistor with 10V across it, needs a power rating P = V/R =10/470 = 0.21W.In this case a standard 0.25W resistor would be suitable.

A 27 resistor with 10V across it, needs a power rating P = V/R =10/27 = 3.7W.A high power resistor with a rating of 5W would be suitable.

Heat sink

Fig.4.2.22

Waste heat is produced in transistors due to the current flowing through them. Heat sinks are

needed for power transistors because they pass large currents. If you find that a transistor is

becoming too hot to touch it certainly needs a heat sink! The heat sink helps to dissipate(remove) the heat by transferring it to the surrounding air.


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CONNECTORS

Connectors are basically used for interface between two. Here we use connectors for

having interface between PCB and 8051 Microprocessor Kit.

There are two types of connectors they are male and female. The one,

which is with pins inside, is female and other is male.

These connectors are having bus wires with them for connection.

For high frequency operation the average circumference of a coaxial cable

must be limited to about one wavelength, in order to reduce multimodal

propagation and eliminate erratic reflection coefficients, power losses, and

signal distortion. The standardization of coaxial connectors during World War

II was mandatory for microwave

Operation to maintain a low reflection coefficient or a low voltage standing

wave ratio.

Seven types of microwave coaxial connectors are as follows:

1. APC-3.5

2. APC-7

3. BNC

4. SMA

5. SMC

6. TNC

7. Type N


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LED (LIGHT EMITTING DIODE)

A junction diode, such as LED, can emit light or exhibit electro

luminescence. Electro luminescence is obtained by injecting minority carriers

into the region of a pn junction where radiative transition takes place. Inradiative transition, there is a transition of electron from the conduction band

to the valence band, which is made possibly by emission of a photon. Thus,

emitted light comes from the hole electron recombination. What is required

is that electrons should make a transition from higher energy level to lower

energy level releasing photon of wavelength corresponding to the energy

difference associated with this transition. In LED the supply of high-energy

electron is provided by forward biasing the diode, thus injecting electrons

into the n-region and holes into p-region.

The pn junction of LED is made from heavily doped material. On forward

bias condition, majority carriers from both sides of the junction cross the

potential barrier and enter the opposite side where they are then minority

carrier and cause local minority carrier population to be larger than normal.

This is termed as minority injection. These excess minority carrier diffuse

away from the junction and recombine with majority carriers.

In LED, every injected electron takes part in a radiative recombination and

hence gives rise to an emitted photon. Under reverse bias no carrier injection

takes place and consequently no photon is emitted. For direct transition from

conduction band to valence band the emission wavelength.

In practice, every electron does not take part in radiative recombination

and hence, the efficiency of the device may be described in terms of the

quantum efficiency which is defined as the rate of emission of photons

divided by the rate of supply of electrons. The number of radiative

recombination, that take place, is usually proportional to the carrier injection

rate and hence to the total current flowing.


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LED Materials:

One of the first materials used for LED is GaAs. This is a direct band

power saving street light

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