FOR KV SCIENCE STUDENTS

1. INVESTEGATORY PROJECT
RAHUL PATEL
CLASS XII C

3.  In the accomplishment of this project successfully, many
people have best owned upon me their blessings and the
heart pledged support, this time I am utilizing to thank all
the people who have been concerned with project.
Primarily I would thank god for being able to complete this
project with success. Then I would like to thank my
principal Mrs. Vinita sharma and physics teacher Mr.
G.P.Singh , whose valuable guidance has been the ones
that helped me patch this project and make it full proof
success his suggestions and his instructions has served as
the major contributor towards the completion of the
project. Then I would like to thank my parents and friends
who have helped me with their valuable suggestions and
guidance has been helpful in various phases of the
completion of the project. Last but not the least I would
like to thank my classmates who have helped me a lot.

4.  This is to certify that Master/ miss ____RAHUL PATEL____of
class XII C of Kendriya Vidyalaya No. 1, Shahibaug
Ahmedabad has completed the Investigatory/ Research
Project on ATOMATIC NIGHT LAMP in physics under the
guidance of Mr. G.P Singh, PGT (Physics) and Mrs. Vinita
Sharma, Principal during the academic year 2017-18 for
AISSC Physics Practical Examination 2017-18

G.P.Singh
Mrs. Vinita Sharma
 (PGT – Physics )
(Principal)
Internal Examiner
External Examiner

5. 1. CERTIFICATE
2.ACKNOWLEDGEMENT
3. AIM OF PROJECT
4.MATERIALS REQUIRED
5.ABSTRACT
6.BLOCK DIAGRAM
7.WORKING
8.PRECAUTIONS
9.END OF THE PROJECT

6.  The main purpose of designing this project
is to prevent loss of current unnecessarily
during day time.
 During night the bulb will automatically
glow.

7.  RELAY
 VOLTAGE REGULATOR
 FUSE
 LIGHT DEPENDENT RESISTOR
 RESISTOR
 TRANSISTOR
 BATTERY
 LED

8.  A street light that automatically switches ON when the night
falls and turns OFF when the sun rises.
 In fact we can use this circuit for implementing any type of
automatic night light.
 The circuit uses a LDR to sense the light .
 When there is light the resistance of LDR will be low.
 So the voltage drop across POT R2 will be high . This keeps the
transistor Q1 ON. The collector of Q1(BC107) is coupled to base
of Q2(SL100).
 So Q2 will be OFF and so do the relay. The bulb will remain
OFF.
 When night falls the resistance of LDR increases to make the
voltage across the POT R2 to decrease below 0.6V.
 This makes transistor Q1 OFF which in turn makes Q2 ON. The
relay will be energized and the bulb will glow. BLOCK

9. LDR
SWITCHING
TRANSISTOR ELECTROMAGNETIC
RELAY
LOAD STATUS
INDICATOR
LOAD
REVERSE EMF
INDICATOR

11.  The main part of this circuit is the light dependent resistor (LDR). It is
a sensor which is a particular kind of resistor whose resistance
decreases when exposed to light. Likewise it offers high resistance in
dark. The resistance value changes from few 100 ohms to mega ohm
range. The LDR is placed in a potential divider network. So voltage
across LDR changes with intensity of light. Voltage across the LDR is
given to the positive terminal of a comparator. Now a reference voltage
is required to compare with the voltage across LDR. That reference
voltage is made by using the pot or preset. So this preset can be used to
adjust the sensitivity of the circuit. Next is the comparator made using
LM358 op-amp which compares the voltage levels at its two inputs and
gives output accordingly. If the voltage at positive terminal is greater,
the output will be high and if the voltage at negative terminal is greater,
the output will be low. That is if it is dark, resistance across LDR is high,
so voltage drop across the LDR is high and voltage at positive terminal
will be greater than the reference voltage. Therefore output of
comparator will be high. The output of comparator is given to
a transistor wired as a switch. Since enough voltage appears across the
base emitter junction, the transistor conducts and current passes
through the relay coils. So relay switches its contact and the bulb glows.
Bulb is connected to the NO (Normally Open) pin of relay as it should be
off when the relay coils are not energized. If the output of comparator is
low, then transistor will be in OFF stage. So no current flows through the
relay and bulb remains in OFF stage

13.  1. Components of the circuit should be
handled carefully.
 2. Care should be taken while soldering as it
may burn the skin.
 3. Connecting wires should be insulated to
prevent disturbance.
 4. Connections should be tight as it may
break easily.
 5. Soldering must be done carefully as it may
burn the PCB board.