Here in this Project, we want to make Darkness sensor using LDR resistor. Basically, LDR is nothing but a Light depending Resistor.A light dependent resistor (LDR) is one whose ohmic value changes with the intensity of light incident on it. This resistor is used in series with the biasing circuit of a switching transistor. The design of the circuit is such that the transistor is switched ON and OFF depending on the threshold value of the intensity of light, the variable parameter being the LDR resistance. Here this article will help you out how to make darkness sensor using 555 timer.
Pin Diagram of 555 timer:
Circuit Diagram for Darkness sensor using 555 timer/LDR:
How to Build Darkness Sensor at your Home:
Output of the Darkness Sensor Detector: