This circuit was obtained from the November 1989 issue of Radio Electronics magazine. The circuit is for motors up to about 1.5 A.
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...