This circuit based project demonstrates the principle and operation behind the darkness detector. For example lamps which switch on automatically in the night. Various decoration lights are needed to be switched on automatically in dark.
The circuit described here is more of a sensor application with a speaker attached to it as output. However, depending upon the application, user can attach a night lamp or series of small LEDs to the circuit too.
Constructed around a 555 timer IC and LDR, this darkness detector circuit uses a 9V battery as a power source along with a couple of passive circuit components: resistance and capacitance.