This sensitive circuit was found in the June 1995 Electronics Now magazine. R1 can be from 10k to 1M depending on the desired sensitivity. Power is supplied by the relay.
This circuit uses common transistors for a fault indicator that turns on an LED and provides an...
The sensor of this circuit is a common silicon diode and it directly drives a small cooler with a...
This circuit found in a documentation of the 90s, uses integrated common at the time, but...