pump control

Discussion in 'The Projects Forum' started by gopal909, Nov 28, 2008.

  1. gopal909

    Thread Starter New Member

    May 28, 2008
    Help, I want to built a circuit which can automatically on the water pump when water in the pipe line and off the pump when water supply stop.
  2. mik3

    Senior Member

    Feb 4, 2008
    From where this water is coming?
    Is it flowing directly into the pump or in a tank and the pump has to empty this tank?
  3. leftyretro

    Active Member

    Nov 25, 2008
    This is a pretty standard application used in the process control area. But to be effective there really needs to be a inlet tank that supplies the suction inlet of the pump feeding from the bottom of the tank. This is usually called a feed surge tank. The feed pipe can enter anywhere to the tank. The logic is usually a simple off/on/automatic field switch. The logic is done by a motor control relay which would need to have two sets of contacts of which one set is rated to handle the current needed to run the motor.

    There needs to be two level type switches installed in the tank. These can be as simple as mercury float switches suspended from the top of the inside of the tank, the low level switch at say 20% height of vessel, high level switch at 80% of vessel. These switch 'tip over' when the liquid causes them to raise when floating, activating their contacts. You need SPDT contacts.

    Modes of operation on the 3 way field switch.

    Off = motor off under all conditions (safety mode)
    On = motor running under all conditions (for testing and initial starting up only)

    Auto = If water in tank is higher then 20% but lower then 80% motor starts and continues to run unless and until the high level switch activates, which then shuts off the motor. Motor will continue to be off until the lower level switch operates and restarts the motor. The inlet valve to the tank should be adjusted such that in normal operation water in equals water out when the pump is running, that way the motor should not have to cycle on and off for normal inlet flow Vs pump outlet flow.

    This is often called an on-off gap controller and is very common. Any industrial electrician should be able to draw out and install the wiring needed.

    Last edited: Nov 28, 2008
  4. Andrew Leigh

    Well-Known Member

    Sep 8, 2008
    Perhaps this will help,

    note that this is the original circuit. You will need to change the position of the sensors I removed the high sensor and place the low sensor at the top of the pipe. You will also need to have the relay go open when the circuit is energised.

    Use Eagle to open the file.


    PS: You may want to make your sensor probe from something that does not rust so that the integrity of the sensor stays intact.