float switch

Discussion in 'The Projects Forum' started by ching fong kee, Jun 23, 2010.

  1. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    hi,i got some problem..
    i got a vertical liquid sensor which is float switch that is use for flood or water spillage..and my sensor is control by the microcontroller,
    then am i need a circuit to operate the float switch?
    or it is a stand alone device?
  2. DickCappels


    Aug 21, 2008
    Most likely, it is a mechanical switch that opens (or closes) when the float rises. If it only has two wires, then that is all it is.

    If it closes when the float rises, you could wire it in series with a bell or a piezoelectric buzzer.

    If it opens when the float rises, then you could use a relay to turn on the bell or buzzer.

    If you want to use it as an input to something more sophisticated, let us know...
  3. retched

    AAC Fanatic!

    Dec 5, 2009
    I agree.

    You may want to go to a hardware store and just take a look at a sump pump. You can see how the float is connected directly to a microswitch to give the 'too high' and 'low' signals to the motor to pump the water.

    You can easily use logic levels to send the info to a microcontroller or whatever you would like.

    Here is a replacement pump-float switch that you can add into your design or just see how it works:
  4. profe

    New Member

    Jun 23, 2010
    The float switch if it is similar to a pressure switch it is a stand alone device. No need for external circuit to act / deact. The question is: what do you want to drive with this particular switch?
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    many floats are simply a magnet and a reed switch. NC/NO dry contacts
  6. Suzukiman

    Active Member

    May 1, 2010
    Floats can also contain a small mercury switch and be suspended to tilt or hang. These are more suitable for sumps and a dirty environment.

    Just treat it as a make or break switch to drive anything you want.
  7. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    thanks you all for replying..
    i found that the switch act like a resistor..it will close when the float rises...
    so when i give a input to the circuit, and when the float is rises, it will perform a closed loop and conduct electricity..so the 10K resistor is it enough to limit the current flow through?
  8. retched

    AAC Fanatic!

    Dec 5, 2009
    No one could know if s 10k resistor will be enough. You have not said what voltage and current the switch will be exposed to.

    Also, you shouldn't need a resistor for a switch.
  9. Wendy


    Mar 24, 2008
    Actually, you can need a pull up or pull down resistor if it is being turned into a digital signal. I've designed my share of such systems, if there is processing involved (nothing sophisticated, just logic) then you are probably going to use the switch as a logic signal instead of driving something directly.

    The switch will last much longer with low current too.

    There is nothing wrong with a float switch, but there are other alternatives, such as optic sensors. If the sensor is wet it also generates a digital signal, and uses 3 wires for the device. I've also messed with my share of ping pong and LED/photosensors to measure fluid levels.

    If the OP wants some help a schematic is always nice. Right now we are spitting in the dark.