Project ReportProject ReportProject ReportProject Report

Project Report

Submitted

On

Light Dependence Resistance

Class – XII

Submitted To:Submitted To:Submitted To:Submitted To: Submitted By:Submitted By:Submitted By:Submitted By:

Miss. Sunita Pankaj Gill

Dept. of Physics Class – XII

Certificate

This is to certify that Pankaj GillPankaj GillPankaj GillPankaj Gill, student of Class XII, Mahendra Model Sr. Sec. SchoolMahendra Model Sr. Sec. SchoolMahendra Model Sr. Sec. SchoolMahendra Model Sr. Sec. School has

completed the project titled Light Dependence Resistance during the academic year 2009-

2010 towards partial fulfillment of credit for the Physics practical evaluation of CBSE 2010,

and submitted satisfactory report, as compiled in the following pages, under my supervision.

Miss. Sunita Miss. Sunita Miss. Sunita Miss. Sunita

Department of Physics

Mahendra Model Sr. Sr. School

Acknowledgements

"There are times when silence speaks so much more loudly than words of praise to only as good as belittle a person, whose words do not express, but only put a veneer over true feelings,

which are of gratitude at this point of time."

I would like to express my sincere gratitude to my physics mentor Miss. Sunita Miss. Sunita Miss. Sunita Miss. Sunita , for her vital

support, guidance and encouragement, without which this project would not have come

forth. I would also like to express my gratitude to the staff of the Department of Physics at

Mahendra Model Sr. Sec. School for their support during the making of this project.

((((Pankaj GillPankaj GillPankaj GillPankaj Gill))))

INTRODUCTION

In the society, some times street lights glow in day time due to

any reason. In mines area people face many difficulties due to

absence of light in the nights. In frontier and hilly areas, people

face many problems due to damaged street lights.

For solve above these problems, we create a device in which

the lights glow in night and in day time, they off automatically

and don't glow. Due to use of it, we can solve above problems

and can also save electricity and men's power.

PRINCIPLE

This project is based on Light Dependent Resistance

(L.D.R0.).LDR is a resistance, in which opposing power of

current depends on the presence of quantity of light present,

i.e. the resistance of LDR increases or decreases, according to

quantity of light which falls on it.

If LDR places in darkness, the resistance of LDR increases and

when light falls on it, the resistance of LDR decreases and act

as a conductor. Any LDR in the presence of light and darkness

changes its resistance is depends on the different types of LDR.

ADVANTAGES

• Collections of parts of the circuit are easily available.

• Accuracy of this circuit is more than accuracy of other

circuits.

• By using laser, it can be used for security purposes.

• It can be used to stop the wastage of electricity.

• The cost of circuit is low.

• This circuit saves the men's power.

USES

• It can be used in street lights.

• It can be used in mines areas.

• It can be used in hilly areas.

• By using laser, it can be used for safety purposes.

• It can be used in frontier areas.

• It can be used in houses.

• It can be used in jail lights.

BRIEF DISCRIPTION OF

COM PONENTS

1. TRANSISTOR:1. TRANSISTOR:1. TRANSISTOR:1. TRANSISTOR: ---- When a thin slice of p-type is

sandwiched between two blocks of n-type, then n-p-n

transistor is formed. It consists of emitter, base, and collector.

In the project, common emitter n-p-n transistor (BC-147 &

SL-100) is used.

2. DIODE2. DIODE2. DIODE2. DIODE: : : : ---- When a p-type and n-type semiconductors are

joined a diode is formed. It conducts when forward biased and

does not conduct when reverse biased. In the project, IN-

4007diode is used.

3. RELAY3. RELAY3. RELAY3. RELAY: : : : ---- It helps to connect and disconnect. In the

project, we use relay of 6 ohms.

4. CARBON RESISTOR4. CARBON RESISTOR4. CARBON RESISTOR4. CARBON RESISTOR: : : : ---- A carbon resistor has generally

four rings or bands A, B, C and D of different colours

corresponding to the value of resistance. In project, we use

carbon resistance of 220 kilo-ohms, 1.5 kilo-ohms and 820

ohms.

5. LDR5. LDR5. LDR5. LDR: : : : ---- LDR means light dependent resistance which is

used to complete the circuit.

6. TRANSFORMER6. TRANSFORMER6. TRANSFORMER6. TRANSFORMER: : : : ---- Transformer is used to convert low

alternating voltage to high alternating voltage by decreasing

the current and vice-versa. We use a transformer of 6-0-6V for

the circuit.

7. CAPACITOR7. CAPACITOR7. CAPACITOR7. CAPACITOR: : : : ---- Capacitor is used to block DC. In the

circuit, we use the capacitor of 220mfd and 1000mfd.

8. BULB: 8. BULB: 8. BULB: 8. BULB: ---- An electric bulb is connected to the circuit when

LDR comes in the darkness.

WORKING

Let 6V. DC is flowed in the circuit. When light falls on LDR

then the resistance of LDR will decrease and approximate

equal to zero. 6V DC come from 220 kilo-ohms resistance

and passes through LDR. At this time, it becomes earth, so

that no voltage flows through the base of transistor T1. Due to

absence of positive voltage at base, emitter hasn't negative

voltage in the comparison of its base, so that transistor T1

don't conduct and no current flows through it. But resistance

of 1.5 kilo-ohms is connected with 6V DC line, so that from

6V DC approximate 4V DC passes through 820 ohms and

reach at the base of transistor T2. For conduction, emitter has

some negative voltage in the comparison of its base. But at this

time, 4V DC reach at base of transistor T2, so that emitter has

highly negative voltage in comparison of its base, so that

transistor T2 highly conducts. The collector of transistor T2 is

connected with relay coil, so that magnetic induction around

relay coil will disconnect with rest point and connect with

active point. So, According to the circuit, the bulb will glow.

Now, when light don't fall on LDR so that the resistance of

LDR increases. Now LDR has not zero resistance due to

darkness, so that 6V DC line and 220 kilo-ohms resistance,

some positive voltage reach at the base of transistor T1.The

collector of transistor T1 has positive voltage because 6V DC

pass through 1.5 kilo-ohms resistance and reach at collector of

transistor T1. In this way transistor T1 conduct and current

start to flow in transistor T1. Transistor T1 and resistance of 1.5

kilo-ohms are connected in series so that the current also flows

through 1.5 kilo-ohms resistance. Now, the above terminal of

1.5 kilo-ohms resistance has 6V DC, it means the lower

terminal of 1.5 kilo-ohms resistance has lower voltage i.e. 3 or

3.5 V. From 3V approximate 1.5 V or 1 V. DC reaches at base

of transistor T2. The collector of transistor T2 has positive

voltage by relay coil. But at this time, emitter has some

negative voltage in the comparison of its base.

So that the quantity of current which flows through transistor

T2 and relay coil will very low. Due to this, magnetic induction

around relay coil will not more effective and pole point will

disconnect with active point and connect with rest point.

According to the circuit, the bulb will glow.