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 name

No. Voltage Resistance Power Current

Transistor C 1383

LED 3 V 15 (mA)

Variable resistor 0-20 K 0.25 W

Resistance 10 K 0.25 W

Resistance 1 K 0.25 W

LDR 4 K -20 k 0.25 W

Calculations

Circuit Diagram

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.

Comments