We found this circuit in the 1964 RCA transistors manual. The sensor may be a common LDR and the transistor BC558. The relay has an operating voltage according to the power supply.
This circuit was found in the June 1991 issue of Radio Electronics magazine. The circuit uses two...
The MOSFETs are of the type of power and the resistors have their values between 1 k and 10 k for...
In the figure we have the way to use an LED to increase the voltage of a zener. The increase...