Night light with transistors

Simple circuit that turns on the light automatically at night

Reading time: <1 minut

How does the project work?

The project has a simple circuit that turns on the light automatically at night. It is based on 2 NPN transistors (BC547) used in Darlington configuration, and a photoresistor. With the help of POT1 the light sensitivity of the LDR photoresistor can be adjusted.

What is the Darlington configuration?

The Darlington configuration consists in connecting the load of a common collector transistor, of another transistor, thus multiplying the amplification factors in the current.

List of required components:

1 x R1 = 120k / 100k
1 x POT1 = 100k
1 x T1 = BC546 / BC547 / 2N2222
1 x T2 = BC546 / BC547 / 2N2222
1 x photoresist (LDR)
4 x LEDs
2 x Terminal contacts
1 x Breadboard test board + connecting wires

For a better understanding of the operation of the circuit and to make this assembly on the breadboard we will need electronic scheme presented below:

Placing components on breadboard

To better understand operation of this project, I have attached the video below:

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