In the figure we then have the complete moisture-activated alarm circuit in which the sensors consist of no more than two wire screens separated by a piece of dry cloth. The screens should be kept tight on this dry fabric which should also be porous.
When water falls on the fabric, its resistance lowers rapidly by firing the circuit (figure 1).
In figure 2 we have the sensor that is made with screens and a piece of porous fabric.
CI - 741 or equivalent
R1 - 100k - trimpot
R2, R3 - 100k x 1/8 W- resistors (brown, black, yellow)
R4 - 100 ohms x 1/4 W - resistor (brown, black, brown)
C1 - 0.1 uF - polyester capacitor
C2 - 100 uF x 16 V - electrolytic capacitor
FTE - 8-ohm speaker
Miscellaneous: sensor (see text), printed circuit board, symmetrical source, wires, solder, etc.
