Sensor Bypass

Discussion in 'The Projects Forum' started by HighVoltage!, Jun 13, 2018.

  1. HighVoltage!

    Thread Starter Member

    Apr 28, 2014
    116
    0
    I want to temporarily bypass a normally open low pressure sensor upon starting a pump. Because there is no pressure, the sensors logic is 0 or OPEN. When When there is pressure above 5psi, the switch will CLOSE.
    The sensor is in series with the 120VAC circuit, in which will de-energize coil if pressure drops.

    Goal: I can probably have a momentary push button in which I can hold to short-out sensor upon starting (DONT LIKE)

    Can I use a time delay relay to energize an auxiliary relay/contact to short out sensor.

    Any other ideas on how to temporarily short-out sensor upon start? Otherwise, pump will not start.


    Thanks
     
  2. HighVoltage!

    Thread Starter Member

    Apr 28, 2014
    116
    0
    Note: This circuit pulls in contacts for 480V pump circuit.
     
  3. danadak

    Well-Known Member

    Mar 10, 2018
    1,750
    359
    A standard well pump under / over pressure switch has a lever attached
    to bellows. When pressure is under user rotates a lever that manually
    closes contacts to pump starting it. As pressure rises bellows inflates and
    slowly takes off required torque on lever until user no longer has to hold it.
    Then pump runs from a low pressure setpoint to high, shuts off, and cycle
    is repeated w/o user intervention when pressure drops , but not all the
    way to kill pump due to total loss of pressure.

    [​IMG]

    Regards, Dana.
     
    HighVoltage! likes this.
  4. HighVoltage!

    Thread Starter Member

    Apr 28, 2014
    116
    0
    This would be ideal. However, there is already an existing lp cut-off switch in which I intend to use somehow ;)
     
  5. HighVoltage!

    Thread Starter Member

    Apr 28, 2014
    116
    0
    The discharge pressure is less than 10psi. The pumptrol is meant for higher pressures.
     
  6. DNA Robotics

    Member

    Jun 13, 2014
    389
    145
    This relay circuit should do it but you need a wall wart power supply or battery to operate the relay.
    Relay bypass circuit.jpg
     
  7. HighVoltage!

    Thread Starter Member

    Apr 28, 2014
    116
    0
    This is great. However, I do not want the pressure switch to remain shorted. Upon reaching a pressure greater than 3psi, I want the switch to NOT be shorted. Under a low prrssure condition, the switch will disengage a latch circuit, resulting in the pump shutting down.
     
  8. DNA Robotics

    Member

    Jun 13, 2014
    389
    145
    It only bypasses when you press the switch to get it started.
    Relay bypass circuit.jpg
     
  9. crutschow

    Expert

    Mar 14, 2008
    20,067
    5,652
    Then all you need is a switch across the contacts as the relay serves no purpose.
    But the TS stated he did not want to have to hold the start button for that long.

    Just use a time-delay relay as the TS suggested.
     
  10. DNA Robotics

    Member

    Jun 13, 2014
    389
    145
    He didn't want to switch 480 volts.
     
  11. crutschow

    Expert

    Mar 14, 2008
    20,067
    5,652
    Of course not.
    The pressure switch controls 120v which controls a relay that switches the 480V to the motor.
    Read all the posts.

    He just doesn't want to have to hold the start button until the pressure builds up above the its pressure setting.
     
Loading...