The sensors of this liquid alarm are formed by two pieces of wire with the ends peeled off. The relay depends on the supply voltage that can be between 3 and 12 V. The transistors can also be the BC548.
Obtained from an English publication, this circuit actually needs a current limiting resistor,...
The voltage regulator circuit described is highly accurate and uses discrete components...
We found this test circuit in the November 1999 issue of Electronics Now magazine. The circuit is to be...