Two transistors with a common collector configuration and connected in a cascaded form constitute a Darlington Pair. While Darlington pairs can be made on a breadboard using a few electronic components, there are IC available that work as them and thus aid in making a circuit simple and easy to be operated.
In this project, the first transistor’s emitter feeds into the second transistor’s base and as a result the input signal gets amplified by the time it reaches the output. When light falls on the LDR, its resistance reduces. The bias voltage is supplied to the transistor and this voltage is enough to make the transistor and relay work. A variable resistor is also connected on the base of transistor to adjust the sensitivity.
Filed Under: Electronic Projects