We found this circuit in the May 1990 issue of Radio Electronics magazine. The circuit is powered by the relay used and uses both normally open and normally closed sensors.
This circuit was found in a 1980s documentation. The low voltage circuit uses a PUT. Transistors can...
June 2017 - Mouser Electronics has a broad line of Cree products for use in horticulture, such as...
The TDA2040 is not a common IC these days, but if you find one you can build this high quality...