This circuit for alternating current loads has a built-in timer. SCR2 is according to the motor current and must be equipped with a heat sink. The circuit is from a 70s GE documentation.
The circuit in the figure is based on an LM101A; diodes can be replaced with equivalents. The...
This circuit, with magnetic sensor, uses an operational amplifier of the time. The circuit is from...
Found in a 90s Popular Electronics, this circuit checks if a remote-control transmitter is...