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Float Valve Circuit Problem

Discussion in 'General Electronics Discussion' started by NLRD, Jan 18, 2018.

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  1. NLRD

    NLRD

    1
    0
    Jan 18, 2018
    Hello guys,
    I am looking for some advice on how to problem solve the current issues with the circuit I designed.

    Project
    Create an timed automatic plant feeding system.

    Objective
    To fill and drain pots connected to a dummy pot. The water level to be controlled by float valves inside the dummy pot and feeding to be activated by a timer.

    Mechanism
    Timer switches on which activates the relay and sends power to pump A in tank which fills dummy pot with water until it reaches the level of the top valve which is NC. The water level rises until it opens the top valve which switches pump A off. Water stays in the pots until the timer switches off, cutting the power to the relay which cuts the power to pump A. The bottom valve which is NO is now closed due to water level, relay returns back to normal position and pump B which sits inside the dummy pot pumps the water back into the tank until the bottom valve becomes open and cuts the power to pump B. This cycle is repeated.

    Issues
    1) Relay buzzes / chatters
    Relay is either flicking on and off or not flicking at all but an electric current can be seen jumping across the switch. Maybe the coil is received not enough voltage/current to keep the coil activated or it is receiving too much.


    2) Both pumps stay on at the same time.
    Circuit B which is constantly on due to the connection should not have any power when the relay switches to activate circuit A. Not sure why it is overpowering the relay. Maybe voltage is too high in live in or too low in live out.

    Tried = Changing the brand of relay, Changing the voltage of relay. 240vac and 230vac as using power from mains. What did work was disconnecting the B circuit where the power stays on constantly and adding a second wire from connection 7 to connection 4 on they relay. This worked while circuit B is not connected but not when it is. Changed the wires, changed the pumps.

    Any advice is helpful. The system does fill even though both pumps are on but would like to stop the relay from buzzing and have only one pump operational at a time. I have attached drawings to aid my description.

    Component Specs
    Power in cable = 250V 13A
    Mechanical timer = 240V
    Pumps = 220-240V 3A
    Relay = 240V 15A & 230V 30A
     

    Attached Files:

  2. Bluejets

    Bluejets

    4,151
    879
    Oct 5, 2014
    Draw your circuits in the normal (power off) mode.
    Do not switch neutrals.
    Appears the way the relay gets it's return (N) is through load A?..........(not a good idea...source of 1 problem)
    Just a quick look but I'll get back to it later(missus wants job done)

    If no one else jumps in beforehand, I'll redraw it for you tonight.
    Cheers...
     
    Last edited: Jan 18, 2018
  3. Bluejets

    Bluejets

    4,151
    879
    Oct 5, 2014
    A bit of misunderstanding here in your description.
    This first part is ok.

    But then this.......
    You just said in the first quote that the level switch controls the pump A.


    This part is also confusing as the relay is no longer powered so I'm assuming it will have to be changed.
    Also, are the 2 units in your sketch adjacent to the "B" pump marked "C" and "D" , the high and low water control level switches?
    What actually operates the timer. Does it cycle continuously or is it just a one-shot device?

    I'll see if I can come up with an "obvious" arrangement to work with in the meantime.
     
  4. Bluejets

    Bluejets

    4,151
    879
    Oct 5, 2014
    NRLD,
    First attempt.
    Timer controls complete run time.
    Float switch is changeover type.
    Position shown is conventional power off, ready to start.
    Only defect is when timer shuts off, cycle remains in that position until next time cycle.
    e.g. If tank is pumping down when timer shuts off, this is where it will start again next time cycle.
    I am assuming the timer is a one-shot device.
     

    Attached Files:

  5. Bluejets

    Bluejets

    4,151
    879
    Oct 5, 2014
    OK...sorted. Hope the bloke is still around. :)

    Details below.

    Starting with Tank B empty, Float switch is in the position A shown on the drawing.

    When the Timer closes, relay RA turns on, which in turn runs Motor-A via RA-1 contacts.

    Disregard RA-2 latch contacts for the moment.

    When Tank B is full, Float switch changes over to position B, stopping Motor-A.

    Float switch position B now feed relay RB, and Motor-B now runs via relay RB-1 contacts.

    Motor-B will continue to run until the Float once again changes to position A.

    If the Timer at this stage is still closed, the above cycle runs again.

    However, should the Timer decide to stop at any time during this “fill” cycle, latching contact RA-2 will keep Motor-A running until Tank B is once again full.

    Float changes to position B, dropping the latch RA-2 and stopping Motor-A.

    Motor-B runs once again until Tank B is empty and the Float switch changes to position A.

    As the Timer has now opened, there is no futher cycling and everything stops until the next Timer closure.

    Circuit is purely for explanation on how it can be done.

    Relay sizes etc. will have to be selected to suit the load.
     

    Attached Files:

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