General Electric suggests this circuit in an 80's documentation. The circuit makes use of PUTs that are not common components today. Note the timing components that may change.
This Sample & Hold circuit configuration is from an American 1980s documentation. The circuit uses...
By LED flashes you can get an idea of the degree of moisture in the soil. The sensors are wires...
Found in an old Popular Electronics, the purpose of this circuit is to give a strong discharge in an...