This indicator or logic probe was found in the April 1979 Radio Electronics magazine. The integrated circuit is the 555 and the FET can be any general-purpose type.
For those who like experimental circuits, here is a sequential flasher system with LEDs, which can be...
This circuit can be used in broilers, greenhouses, drying chambers to regulate the temperature in a simple...
This circuit consists of an electrostatic sensor that can check if a cable is energized by simply...