This simple circuit was found in the August 1984 issue of Radio Electronics magazine. The circuit monitors the power supply to a computer and has a backup battery.
Photoelectric cells can be used as sensitive light sensors. However, the low voltage they generate...
With the illustrated circuit we can run a DC motor in one direction or the other, depending on...
In this circuit the relay triggers on when light falls onto the sensor, a common LDR. Power supply...