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Problem: electrolysis & lime coating wires

  1. Mar 17, 2009 #1
    Hi all.

    I build a project that detects the level of the water reservoir and shows that digitally using the 7-segment display.... It worked...
    This requires a wire with positive voltage (5V) to be at the bottom of the water reservoir (it's a copper - network wire) and a number of detecting/sensor lines (wires) at each level to be detected.... I hope I explained it clearly:confused:
    The problem is that the wires become coated with lime (the sensing wires/at the levels, these wires become connected to the negative terminal when water covers them) and the positive wire at the bottom becomes coated with green and white materials... this prevents current to flow between the wires as it should and then the project do not work probebly.. When I clean the wires it works perfect but after some hours it comes back to the same problem.....

    What do you advice me to do?? how could I solve this obstacle??

  2. jcsd
  3. Mar 17, 2009 #2
    This circuit (EDN 2001) uses ac signals and capacitance to measure water level. There is no DC water conductance measurement.

    Attached Files:

  4. Mar 17, 2009 #3
    It sounds like you have created a small electrolytic cell. The wire itself participates in chemical reactions so it eventually becomes coated with this greenish junk. Eventually, the wire will probably crumble due to deterioration. Using stainless steel for the portion of the circuit in the water may be better in the long run. It won't deteriorate as quickly. Yet do note that it isn't as conductive as copper either.
  5. Mar 18, 2009 #4


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    Science Advisor

    BobS is correct here. You just don't want to detect water by running current through it. Measure the capacitance instead, it's how it's how 'real' sensors do it.
  6. Mar 18, 2009 #5
    The project is a water level inditicator that shows digitally the number of water barrels in a reservoir. It works fine, but my only problem is the chemical reactions that are happening... they are makes the wires (in the water) coated with lime and greenish materials, these materials are the problem, they are preventing current flow..... After I cleaned the wires, the device worked and it still working for now... (about 30 hour till now..). Maybe stainless is a good idea, I will ask a chemistry instructor for this purpose anyway...
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