We found this circuit in the April 1982 Radio Electronics magazine. It contains a good power stage whose transistor must be mounted on a good heat sink.
SST LLE Series Liquid Level Sensor Switches Available through Mouser Electronics, these solid...
The first circuit is shown in figure 3 and uses a 2N2222 transistor or equivalent. This circuit can...
This circuit shows how an inductive capacitance can be used to reduce the voltage of Power supply...