turns ON the light when it gets dark around

1. Light Sensor Night Switching
Equipment List
Equipment name Quantity used in a circuit Quantity used in
Whole Project
Transistor (npn) 2 60
LEDs (White) 2 60
Variable Resistor 1 30
Resistance (10K) 1 30
Resistance (1K) 1 30
LDR 1 30
Specifications
Equipment No. Voltage Resistance Power Current
name
Transistor C 1383
LED 3V 15 (mA)
Variable resistor 0-20 K 0.25 W
Resistance 10 K 0.25 W
Resistance 1K 0.25 W
LDR 4 K -20 k 0.25 W

2. Calculations

3. Circuit Diagram

4. Theory/ Basic Principle
We have to make the Light Sensor Night Switching. We used two Transistor one LDR, one
variable resistance,10 k resistance,1 K resistance two LEDs and Input Source of 9 V .we
connected a resistance of 1k in Series with Base of transistor (T1) and also Connected the
other components of the circuit as shown in the circuit diagram. We Used the common
Emitter Configuration of the transistor in this circuit.
If we used only one transistor than the circuit will be day light switching we have to make
the night switching so we inverted the output by connecting the base of other Transistor
with the collector of first transistor.
Transistor (T1) is ON when light is falling on the LDR because the voltage drop across the
variable resistor is greater than 0.6 volt so that’s why the Emitter Collector is Shorted all
current passes through this and Transistor (T2) is turned OFF we are getting the output
across T2 so when light is falling we got no output when light is not falling than T1 is OFF
and T2 is ON so as we got the output in dark. we connected the LEDs to check the output.
This the basic principle of our project.
This the concept of single circuit in our project. we connected 30 such circuit in the project
and controlled these individually.
We make the circuit such sensitive that it can response to the shadow of your figure in no
time.
Result
The result of our project is that it turned ON in the dark and turned OFF when light is falling
on it. We have shown the output by glowing LEDs.
This is the circuit that Engr.Sohail Afzal Assign us.
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