We found this circuit in an Electronics Now from the 1990s. The circuit crashes when light strikes the sensor. Instead of the alarm a relay can be used to drive higher power devices.
This circuit, which can be found elsewhere on this website, uses a 741 operational amplifier and a...
This circuit can act as a receiver for the transmitter of the previous circuit. We found it in...
This circuit makes use of an unusual component which is a large surface diode that can be used to...