Water Activated Relay

Posted on Feb 7, 2014

In his circuit Marin has used two transistors wired as a high gain compound pair. Transistor T1 may be a 2N2222A and T2 a BC108. The current gain will be the product of each transistors beta, which will be a minimum of 140 x 110 or 15400.

Water Activated Relay
Click here to download the full size of the above Circuit.

The power supply used can be any voltage from 4. 5 to 15 volts, a typical 5 volt relay may require 60 mA to operate, in which case any fluid which passes a minimum current of 4 uA will activate the relay. This is easily achieved with tap or rain water.

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