We found this circuit in the 1983 Radio Electronics Special projects magazine. The components are common, and the circuit drives a relay. The power supply must be isolated.
This circuit makes use of an operational amplifier from the 80's. The circuit can be implemented with...
When the power is cut off, this circuit keeps the flashlight on for a while, allowing it to be...
Using the CK722 this directional photometer was published in Radio Electronics magazine in July...