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.
If the input voltage falls below 12 V the LED glows up. Other voltages can be monitored by...
The diagram shows a tone control with the LM381 IC. The circuit is from a Radio Electronics from...
In other circuits we have seen a circuit for this application whose calculations have been...