We found this circuit in the October 1996 Electronics Now magazine. The circuit uses LDRs as sensors and drives relays. The relays must have voltages according to the power supply.
This TTL bistable or flip-flop with the 7400 was found in an 80's publication. It is a didactic...
This circuit amplifies the signals of an operational amplifier with output values that depend on...
In the figure we have the simple way to use a low current switch or sensor to drive a high power...