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Topic: How do I use these water sensors? (Read 3456 times) previous topic - next topic


Mar 22, 2013, 08:37 am Last Edit: Mar 22, 2013, 08:57 am by RedSquirrel Reason: 1
I bought 10 of these so I can put around my basement in spots that were once prone to get water as I am working on finishing it.


How do I use them?  I thought I  put ground on the "-", +5v on the "+" and channel pin on the "S" but clearly that's not how they work, because I just made one go up in smoke that way.  I wet my finger and put it on to test, turned around to look at the result in my monitoring software, I turned around and all I see is smoke.  Definite fire hazard if I had these all over the place... wow.  What did I do wrong?  Also seems odd that the electronics on it arn't really sealed given this is suppose to get wet.  I did not wet that part though, I plan to seal those myself somehow.   I know I could make my own quite easily but it's nice that these have the pull down/up resistor built in so it saves me from having to salvage a resistor of the right resistance out of something.

Edit: Just tried another and it works ok, maybe this one was defective or something.  I'm kind of nervous about putting these around the house though. Did not realize 5 volts was enough to make something catch on fire.  I guess it's the current that matters.  I could look at using a current limited power supply maybe, to be safe.


Yes you seem to be doing it right.
It sounds like you had a short on the first one. The conductors are very thin so they can burn with not too. Uh current. We're they powered from the USB line?


For power I have a DIN rail bus with +5v and +12v powered by the power supply in my environmental server. So it has access to probably a decent amount of current.   What would be the best way of perhaps limiting that?  Could probably limit it to like 2 amps. Or perhaps I should have a high current bus (for stuff that actually uses the power directly such as the HHO sensor) and a low current bus, for everything else.


What do you want to test ?

Actually real water or something humid or moisture ? Soil ? a damp wall ? humidity ?


For power I have a DIN rail bus with +5v and +12v powered by the power supply in my environmental server.

Ok, well someone has to ask  8) .... you sure you didn't stick 12V thru it not 5?
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What do you want to test ?

Actually real water or something humid or moisture ? Soil ? a damp wall ? humidity ?

Just water, these will be placed around my basement in case of water leak.  I was just testing it to ensure it works, and also testing to make sure it will trigger an alarm.  I have a system for various monitoring.

For power, I had it temporarily connected through my ethernet patch panel so I did not have access to the 12v rail from upstairs, I had ground +5 and channel hooked up only.  Though now that I think about it, I wonder if I accidentally reversed it the first time.


Finding the home site (given on the back of the sensor!), www.robotbase.cn, it was possible to find better
pictures of the board (both sides).

Its wired like a phototransistor(!) to + and - pins only.   The leakage current from the traces goes to the base of
the transistor - without current limiting its going to be very easy to burn out the transistor.

You should put a 1k resistor from the + pin to a digital pin, wire - to ground, ignore the S pin (its assuming
standard 3-wire servo connectors).  Then take the + pin also to an analog input.

To use drive the digital pin high to energize, read the analog level, then remove the drive to the digital
pin (this stops you being electrolysing the water and corroding the sensor away).

Its sensitivity will depend very strongly on the ionic concentration of the water sampled, note.
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Actually I did notice it corrodes the sensor when there's water.  Guess these arn't really that great then.  I bought them as it's a nice little package and I don't have to worry about trying to find resistors or other components.  I kinda wish I had started collecting this stuff way before instead of just throwing out electronics.   I'm also kind of bummed that these are normally open, was hoping it would be normally closed, that way if the wire breaks or something like that, it will trigger the alarm.

Also, think I could actually wire these in parallel? I'm thinking if I can find a 10kish resistor (still have a UPS board to pick stuff off of) I could perhaps connect all of these together, but then have the +5v have a resistor before it fans out to each unit.  It would limit the current and perhaps reduce the chance of an issue?  I'm also connecting these to a digital pin, is this an issue?  I know they're meant for analog, but I just need a yes/no reading and given there are more digital pins than analog I rather use them.


Hi, I've buyed the same sensor.

Can you please explain me how to connect using breadboard and which code have you use to get it working?

Thank you in advanced

Best Regards

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