This bistable circuit that drives a relay with a pushbutton was found in the March 1pp6 issue of Electronics Now magazine. A common bipolar with a 1k resistor at the base can be used in place of the FET.
In this 2002 circuit, we have the activation when the reservoir is empty and shutdown when full....
This circuit was found in a 2001 documentation. It is a test of zener diodes that uses a voltmeter or...
The output current is of the order of 100 mA maximum, but the transistor used can be changed for...