Water Activated Relay circuit
For electronic circuit has two transistors wired as a pair, together with high gain.
2N2222A transistor T1 and T2 is BC108.
The actual profit will be the proceeds of any beta-transistors with a minimum of 140 x 110 or 15,400.
Power supply is a voltage from 4.5 to 15 volts, a kind of relay 5 Volt at 60 mA is required to in this case, any liquid with a stream of at least 4 others to the relay. It is easy to reach with tap water or rain.
3 Responses
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Why cant you just use 6 volts dc to probes without any extra transistors and resistors? On voltmeter i get 5 volts from running wires to wet sponge or directly in a glass of water. It’s enough to trigger the 5volt relay. Is this approach destroying the battery?
@JohnH – There are so many reasons why that’s not a good idea.
First, you may be seeing 5 volts, but how much current will flow through the water? I bet the water won’t conduct enough current to activate the relay. Try it – I bet it doesn’t work. Remember, voltage isn’t everything. When you shuffle across the floor on a dry winter day and get a static spark when you touch a doorknob, that’s roughly 10,000 volts. It doesn’t kill you because the current is extremely low. So, volts and amps are two different things. Just because you see 5 volts through the water doesn’t mean you’ll get the current needed to energize the coil in the relay.
Second, it’s not reliable. Mineral content in the liquid will change its conductivity. Pure water is actually a very poor conductor – it’s the minerals in it that allow it to conduct electricity relatively well (I bet your sponge contains all kinds of minerals that are helping the conductivity).
Also, the liquid you’re sticking the probes into may very well be an earth-ground, and it’s just bad practice to run electricity into an earth ground, even if it’s from a battery.
There are other reasons as well, but overall what it boils down to is that it won’t work well (if at all), it certainly won’t be reliable, and it’s a bad design. Much better to use a transistor circuit to properly activate the relay.
When I using power from adaptor the relay will make sound derrrrr like vibrating. What happen in this condition ?