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Topic: Arduino UNO simple single point water level indicator help! (Read 2 times) previous topic - next topic

Jack Christensen

Corrosion requires current, yes? How much current flows into a MOSFET gate?
I'd try using two pins rather than sensing to ground.
One pin is a digital output, drive it high to deliver a sense voltage for just a few milliseconds, the rest of the time make it an input pin (i.e. high impedance). The other pin is an analog input as already configured.
Use a resistor in series with each pin, maybe 10K or even 100K.
If the electrodes were stainless steel, I wonder how much corrosion would occur with this setup.
But the electrodes could still be reversed as Rob suggests.

I wouldn't worry about some variation in readings. Just define two thresholds, e.g. 800 or more means there is water, 200 or less means there is no water. Keep a state variable that doesn't change unless one of the thresholds is exceeded. With that amount of hysteresis, it should work well. Mount the electrodes solidly so that the spacing doesn't change.

MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

Dulimir

Wow thanks guys!
using a digital pin to drive the circuit for a short amount of time just to take a measurement sounds like the simplest way, ill give that a try!

i thought of maybe tinning the copper wires beforehand, maybe that would slow corrosion down even more?
even if there is no current, they will corrode eventually, if they last 6 months its good!
its only a stop gap measure to prevent a submersible water pump from ingesting air.

Thanks again!

Tumbleweed

Easy and cheap http://www.ebay.com/itm/New-Liquid-Water-Level-Sensor-Right-Angle-Float-Switch-/230697910942?pt=LH_DefaultDomain_0&hash=item35b6aac29e, second result of thousands for "water level switch" on E-bay. Or use a straight one on a pipe if you can't drill a hole in your supply tank.
Einstein once said you don't really understand anything until you can explain it to your Grandmother

Jack Christensen


i thought of maybe tinning the copper wires beforehand, maybe that would slow corrosion down even more?
even if there is no current, they will corrode eventually, if they last 6 months its good!


I have a high-water alarm where I just used some stainless steel bolts from the hardware store as electrodes. But they're out of the water most of the time, your project would obviously be the opposite.
MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

emiel

Hi,

Just tested the above water level meter (the code and alternating input on digital 4 and 5) And it works great.
I have one added problem and that is that the water tank is metal en grounded. So it shorts out the signalling to the arduino.
Any suggestions on how to overcome this ?.
I am bound to use the 3 Stainless steel rodds that are allready in place, on is main, 2 and 3 are level low and high.
Any help would be great.

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