This circuit was found in an article about the 555 in the November 1992 Radio Electronics magazine. The circuit uses a 12 V relay and has two timing ranges.
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...