Found in a Popular Electronics from the 1990s, this circuit monitors the voltage of a power supply or battery. The trigger voltage is adjusted with a potentiometer.
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...