HELP! Wiring Optical Water Level Sensor

Discussion in 'The Projects Forum' started by mscarlato, Apr 22, 2010.

  1. mscarlato

    Thread Starter New Member

    Apr 22, 2010
    Hello all,

    I was hoping someone could help me with the wiring of an optical water level sensor for a auto topoff system I am constructing. I am very inexperienced in this type of thing, although I know alot about home wiring. I have a model 0ls-11 optical level switch. I have a DPDT switch with relay block. I have a 12v Adapter. I am trying to accomplish the External Load with 1 Supply wiring as shown here . I am running into problems. Below is how I think it should be wired:

    Positive from the AC Adapter is connected to red wire from sensor. This is then attached to the positive terminal on the relay.

    Negative from the AC adapter is connected to the black wire from the sensor.

    White wire from the sensor is connected to negative terminal on the relay.

    Pump positive is wired to either NO or NC on relay (do you know which is for opening the valve when no water is present?)

    Pump negative is wired to the negative terminal of the relay.

    Is this correct? Also, I don't know where or how to insert a diode. I think it should go at the positive terminal. Is this correct?

    Remember guys, I am really new to this, so please explain it to me like I am a five year old. If you have pictures it would be even better!
  2. JDT

    Well-Known Member

    Feb 12, 2009
    Use the circuit "External load with 1 supply". Load is your relay coil. The relay coil is not normally polarity sensitive unless it has a diode internally fitted. Relay coils often marked A1 and A2. A1 normally +ve. If it has not got an internal diode then you should use an external diode across your relay coil as shown. Cathode of the diode (pointed end on the symbol) - usually marked with a white band goes to the positive supply. Just as shown on the diagram. 1A diode should be OK (1N4000/1/2/3 series). 10-28VDC is your 12V adaptor. The polarity of the supply is important!

    Try this out before connecting your pump. To see if the relay switches correctly.

    Not sure what sort of pump your are using. But once your relay works then it should be a simple matter of switching the pump using the relay contacts. The relay contacts will be the only link between the sensor and the pump. If the pump is also 12V use a different power supply for the pump as the pump may take a heavy load when it starts and effect the sensor operation.
  3. Wendy


    Mar 24, 2008