Abstract

MINI PROJECT REPORT 2010-11 GPTC MEPPADI

ABSTRACT

Project work has an important position in the syllabuses of Diploma courses in engineering science. Project work is meant to make or fabricate product, which are useful for the public .The project work gives the student a chance to apply this theoretical knowledge into practical situations.

Various equipments fabricated under project work will not only enhance the skill of students but also aid for the development of our community. Project work selected by the student may involve improvement of existing machines, invention of new devices, reduction of manufacturing cost, etc...

DEPARTMENT OF ELECTRONICS


CONTENTS

INTRODUCTION

CIRCUIT DIAGRAM

THEORY

WORKING

PARTS OF THE AUTOMATIC STREET LIGHT

BLOCK DIAGRAM

ADVANTAGES

APPLICATIONS

COMPONENT LIST

COMPONENT COST

CONCLUSION

REFERENCE



INTRODUCTION

Automatic Street light needs no manual operation for switching ON and OFF. It detects itself whether there is a need for light or not. When the light intensity decreases below certain level, the street light will be switched ON and when there is other source of light i.e. day time, the street light gets OFF.

The sensitivity of the street light can also be adjusted. In our project we have used LEDs instead of bulb. A Relay (electromagnetic switch) connected at the output of pin 3 of IC 555 will enable the circuit to control a high power supply to any other electrical equipments.



CIRCUIT DIAGRAM

THEORY

This circuit uses a popular timer IC 555. IC 555 is connected as a comparator with pin-6 connected with positively rail; the output goes high (1) when the trigger pin-2 is at lower than 1/3 rd level of the supply voltage. Conversely the output goes low (0) when it is above 1/3 rd level. So small change in the voltage of pin-2 is enough to change the level of output (pin-3) from 1 to 0 and 0 to 1. The output has only two states, high



and low and cannot remain in any intermediate stage. It is powered by a 9v battery for portable use.

The circuit is economic in power consumption. Pin-4, 6 and 8 is connected to the positive supply and pin-1 is grounded. To detect the present of an object we have used LDR and a source of light. LDR is a special type of resistance whose value depends on the brightness of the light which is falling on it. It has resistance of about 1 mega ohm when in total darkness, but a resistance of only about 5k ohms when brightness illuminated. It responds to a large part of light spectrum.

We have made a potential divider circuit with LDR and 100k variable resistance connected in series. We know that voltage is directly proportional to conductance. So more voltage we will get from this divider when LDR is getting light and low voltage in darkness. This divided voltage is given to pin-2 of IC 555. Variable resistance is so adjusted that it crosses potential of 1/3rd in brightness and fall below 1/3rd in darkness.

Sensitiveness can be adjusted by this variable resistance. As soon as LDR gets dark the voltage of pin-2 drops 1/3 rd of the supply voltage and pin-3 gets high and LED or buzzer which is connected to the output gets activated.

WORKING

When light falls on the LDR, it's resistance decreases which results in increase of the voltage at pin-2 of the IC 555. IC 555 has got inbuilt comparator, which compares between the input voltage from pin-2 and 1/3rd of the power supply voltage. When input falls below 1/3rd then output is set high otherwise it is set low. Since in brightness, input voltage



rises so we obtain no positive voltage at output of pin-3 to drive relay or LED, besides in poor light condition we get output to energize.

Precautions:

LDR used should be sensitive. (Before using in the circuit it should be tested with multimeter.)

IC should not be heated too much while soldering. It may destroy the IC. For safety and ease to replace, use of IC base is suggested. While placing the IC pin no 1 should be made sure at right hole.

Opposite polarity of battery can destroy IC so check the polarity before switching ON the circuit. One should use diode in series with switch for safety since diode allows flowing current in one direction only.

Check the biasing of LED since it glows only when forward biased. LDR should be so adjusted that it should not get light from

streetlight itself.

MONOSTABLE OPERATION OF 5551C



Monostable multivibrator often called a one shot multivibrator. It is a pulse generating circuit in which the duration of the pulse is determined by the RC network, connected externally to the 555 timer. In a stable or standby

state, the output of the circuit is approximately zero or a logic-low level. When external trigger pulse is applied output is forced to go high (–Vcc). The time for which output remains high is determined by the external RC network connected to the timer. At the end of the timing interval, the output automatically reverts back to its logic-low stable state.

The output stays low until trigger pulse is again applied. Then the cycle repeats. The monostable circuit has only one stable state (output low) hence the name monostable.

Initially when the circuit, is in the stable state i.e. when the output is low, transistor Q1 is ON and the capacitor C is shorted out to ground. Upon the application



of a negative trigger pulse to pin 2, transistor Q1 is turned OFF, which releases the short circuit across the external capacitor C and drives the output high. The capacitor C now starts charging up towards Vcc through R. When the voltage across, the capacitor becomes 2/3 Vcc, comparator 1's output switches from low to high, which in turn drives the output to its low state via the output of the flip-flop. At the same time the output of the flip-flop turns transistor Q1 ON and hence the capacitor C rapidly discharges through the transistor. The output of the monostable remains low until a trigger pulse is again applied. Then the cycle repeats. The pulse width of the trigger input must be smaller than the expected pulse width of the output waveform. Also the trigger pulse must be a negative going input signal with amplitude larger than 1/3 Vcc.

PARTS OF AUTOMATIC STREET LIGHT



Battery

For 9v power supply we can use 6 pcs dry cell or 6F22 9V single piece battery.

Switch

Any general purpose switch is used as circuit breaker.

LDR (Light Depending Resistor)

It is a special type of resistance whose value depends on the intensity of light which is falling on it. It has resistance of about 1 mega ohm when in total darkness, but a resistance of only about 5k ohms in high intensity of light. It responds to a large part of light spectrum.

LED:

A diode is a component that only allows electricity to flow in one way. It can be thought as a sort of one way street for electrons. Because of this characteristic, diodes are used to transform or rectify AC voltage into a DC voltage. Diodes have two connections an anode and a cathode. The cathode is the end on the schematic with the point of the triangle pointing towards a line. In other words, the triangle points towards that cathode. The anode is, of course, opposite end. Current flows from the anode to the cathode. Light emitting diodes, or LEDs, differ from regular diodes in that when a voltage is applied, they emit light. This light can be red (most common), green, yellow, orange, blue (not very common), or infra-red. LEDs are used as indicators, transmitters, etc. Most likely, an LED will never burn out like a regular lamp and it requires less current. Since LEDs act like regular diodes and will form a short if connected between + and - , a current limiting resistor is used to prevent that very thing. LEDs may or may not be drawn with the circle surrounding them.

Variable resistance: (Potentiometer)

Resistors are one of the most common electronic components. A resistor is a



device that limits, or resists current. The current limiting ability of resistance is measured in ohms, represented by the Greek symbol omega. We can adjust the resistance by turning a shaft. This shaft moves a wiper across the actual resistor element. By changing the amount of resistor between the wiper connection and the connection (s) to the resistor element, you can change the resistance.

PCB: (Printed Circuit Board)

With the help of PCB it is easy to assemble circuit with neat and clean end products. PCB is made of Bakelite with surface pasted with copper track-layout. For each components leg hole is made. Connection pin is passed through the hole and is soldered.

BLOCK DIAGRAM



ADVANTAGES



Easy to construct.

Less cost and less expensive

Simple operation.

It can be used as Bed Lamp or streetlight.

APPLICATION



It is used in streetlight.

It is used in automatic lamp like Bed Lamp.

COMPONENT LIST



RESISTOR

a. 470 Ohms

b. 47 k (Variable)

LDR (Light Depending Resistance)

IC NE555

LED (Light Emitting Diode)

Battery (9V DC)

Switch

PCB (General Purpose)

COMPONENT COST

COMPONENTS VALUE AMOUNT QUANTITY TOTAL



Resistor

470 ohms 0.25 2 0.50

47 k(Variable)

7.00 1 7.00

LDR 5.00 1 5.00

IC NE555 5.00 1 5.00

LED(Red colour) 1.00 6 6.00

Battery 9V DC 15.00 1 15.00

Switch 5.00 1 5.00

PCB(Generalpurpose)

8.00 1 8.00

Total Price of Components (for 1 piece Automatic Streetlight) 51.50

CONCLUSION

I am very happy to attend the project work. This project work helped me to earn more technical knowledge. Many people helped me in this project . I shall be thankful to my parents, respectable teachers,



classmates and all other friends.

REFERENCE

A Text Book of Applied Electronics



R. S. SEDHA

Fundamentals of Digital Electronics

A. Anand Kumar

Electronics for You Magazine

www.circuitstoday.com

ACKNOWLEDGEMENT

We are taking this opportunity to express our thanks to our Principal Mr. NARAYAN NAIK Sir for permission made this project possible.



We here our acknowledgement with deep sense of gratitude to the very valuable guidance of department head Mr. JOHNSON Sir and the project guide Miss. SHAMEENA for without whole help it wouldn't have a possible to complete this project. We are very indebted to our department teachers of GPTC MEPPADI especially for Mr. THANKACHAN Sir and Mr. JAISON Sir for the proper guidance and encouragement given to me in conducting the project successfully.

We also express our sincere thanks all teachers of our college, lab assistance of electronics lab, our classmates and friends for the i r c rea t ive coopera t ion in comple t ing the projec t t imely .

AKHILNATH.VJAMSHEER.P.C


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