This circuit was obtained in a technical documentation from the 70s, but it can be assembled with a BC558 and a SCR of the TIC series. Remember that the SCR has a drop of 2 V when driving, which must be compensated for in the supply. A relay can be used instead of the alarm. We suggest a 6 V relay with a 9 V supply. The sensor consists of wires or metal bars that must contact water or moisture for the trigger. Do not use a source without a transformer to power this circuit.
