Electronic Bilge Switch

gm280

Supreme Mariner
Joined
Jun 26, 2011
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I see a lot of folks talk about installing automatic bilge pump capabilities in their boats. But I also hear of float type switches failing or sticking on and either draining their batteries or burning up the bilge pump, or even worst not turning on bilge pumps and their boats fill up and sink. And I certainly can understand either condition and wouldn't want either or of them to happen to my boat. So I designed and used this electronic bilge switch circuit and used it for over ten years without any problem what so ever. I know there are commercial electronic devices and they probably work similar as well. But if you're wanting to make one yourself, here is everything you'll need to know to build one and use it in your boat...at your own risk, I may add. I assume zero responsibility because I won't be make it or installing it! That is my disclaimer!
Auto Bilge Switch.gif

The actual size of the circuit board is 2.25" by 1". So it is reasonable small. And you can make most any type metal probes you can think of. I used copper house type wires and you can install them inside a small piece of PVC pipe with small holes drilled into the pipe to allow water to enter but block and type debris. And this circuit draws zero current until it senses water, then it turns on and pumps the water out and shuts off again and waits... But don't put the water probes against the hull. Install them a little higher so it doesn't stay running with touching a wet hull bottom. Basically set the probe height to the level you want the pump to turn on. Resistor R1 and R3, are inline to the water probes and keeps 12 volts from shorting to ground. But allow roughly 6 milliamps flow when water touches the probes. Transistors Q1 and Q2 are setup in a Darlington Configuration for huge gains to switch the relay on. The relay is available most everywhere electronic parts are sold. And the diode keeps EMF from taking out the relay. Not many parts so it is clean and neat and it works... Hope you can make one and use it. :thumb:
 
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