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Float switch circuit for fish tank

Discussion in 'General Electronics Discussion' started by chubby190, Nov 20, 2010.

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  1. chubby190

    chubby190

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    Nov 20, 2010
    I have two float switches set in my fish tank. My intention is to have a high-level and a low level switch run a water pump that circulates water between the tank and a sump-filter.

    I have a couple relays, but I can't figure out how to get the thing to work. If anyone has ever worked on a sewer lift station you'll know what I want.

    I want the water lower until the lower-limit float switch is tripped. Then the motor should come on until the high limit switch is tripped. My issue is that between the two switches I have two conditions; when water level is between float switches and is rising the pump is on. Alternatively when water level is between float switched and is falling the pump is off.

    I know there's a basic way to wire a trap so that there are two conditions. Any help would be appreciated.

    What I have: 4 poll double throw relay, one poll double throw relay (which will be activated by 12VDC and run 110VAC motor circuit.

    One float switch is NC/NO reversible (float=on or float=off) the other is NC (float=off)
     
  2. KMoffett

    KMoffett

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    Jan 21, 2009
    I think it can be done, but what do you mean by "float=on" and "float=off"?

    Ken
     
  3. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Ex-sewer worker here.
    If your float switches are the same, (it matters if they're normally open or normally closed), wire your circuit for each switch to operate opposite of one another.
    It's senseless to describe circuit wiring not knowing if your float switches are NO or NC.
    Just think about it. At high-level, you want the switch to trip your circuit. On low level, you want that switch to trip at exactly the opposite water level.
    Pay attention to they type of switch you have, but it's the wiring of your circuit that does the job.
     
  4. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Wrote a nice addition, and site timed-out on me, ....
    One more time, ....
    I reread post.
    Use one relay.
    Wire one set of contacts on relay to interrupt the power to the relay coil.
    Low level switch activates relay, sending water into tank.
    High level switch interrupts power to relay, stopping water flow when at right level.
    Wire the contact circuit through the relay, so that when the high level switch opens the power circuit to the relay coil, the circuit for the low level switch activation is intact.
    Hope this made sense, I'm tired rewriting this when I time-out.
     
  5. chubby190

    chubby190

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    0
    Nov 20, 2010
    Sorry I should have been more clear. Float=on means that when the switch is submersed, or floating, the circuit is closed/on.

    To Shrtrnd:

    The only issue with that (unless I am misunderstanding you) is that when the water is between the two floats I need the circuit to operate two different ways. If I simply wire the relay to be motor on above lower float and off above higher float, the relay will keep cycling as soon as the water level drops below the high level switch.
     
  6. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Nope.
    I don't know how to post drawings on this thing, if my kids visit me for the holidays, I'll see if they can show me how to do that on these fancy computer websites.
    Try drawing the circuit out yourself there.
    The relay is de-energized, and at rest.
    The low-level switch closes the circuit to the relay power, the relay activates, and water flows to fill your tank.
    The high level switch is wired normally closed into your relay coil power circuit, when the water in the tank gets high enough to trip the high level switch, the relay power circuit opens, and the relay resets to it's original, 'at-rest' condition.
    Design the wiring through the relay's own contacts, to route the relay's own coil power, through relay's own contacts for energizing and de-energizing the relay.
    It's frustrating to not know how to post a picture of a drawing here, but the circuit works, I've used it enough in sump configurations.
     
  7. KMoffett

    KMoffett

    719
    73
    Jan 21, 2009
    per your description of the switches and shrtrnd's description of a circuit

    Ken
     

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