Reversing Polarity Device Question

Discussion in 'General Electronics Chat' started by Ken888, May 13, 2013.

  1. Ken888

    Thread Starter New Member

    Apr 8, 2013
    13
    0
    Hi

    I have a 12v DC solidnoid ball valve to disconnect water flow, with two wires.
    You have to reverse the polarity to open or close it.

    I have a pair of 12v wires that when live, trigger it to open.
    But what components do I need to close it ?
    As when the power goes off the trigger wires the valve is still open.

    Any help would be great.

    Ken
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    I would use a relay with a set of double pole change over contacts, when the relay is on it opens the valve , when its de-energised it reverses the power,

    if it doesn't need the power on to maintain open or closed, use a 555 timer to operate the relay.
     
    Last edited: May 13, 2013
  3. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
    A DPDT switch.
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,033
    3,241
    What signal do you want to use to operate the valve? Do you want to use a toggle switch or push-button? Can you apply continuous power to the valve?
     
  5. Ken888

    Thread Starter New Member

    Apr 8, 2013
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    The 12v DC ball valve can have continuous power.
    It gets 12v trigger from a differential controller.
    Which opens the valve. But when the trigger voltage stops I need the valve to shut, and therefore the valve wires have to be switched.
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,033
    3,241
    How often does the valve open and close? If not frequently, you could use a DPDT relay to perform the function. If it's frequent, you could use a transistor H-bridge.
     
  7. #12

    Expert

    Nov 30, 2010
    16,330
    6,818
    Here's another idea: A double pole relay that relaxes to the "closed" condition. It would only open the valve when it gets a signal from the controller.

    Wait...Dodgy Dave already said this in slightly different words,
    but I did a drawing...
     
    Last edited: May 13, 2013
    Dodgydave likes this.
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    If you are manually switching it, you could just use a DPDT "centre off" switch. :)
     
  9. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    Can you give us the model number of the valve so we can see how it's used, it maybe a motorised valve?
     
  10. Ken888

    Thread Starter New Member

    Apr 8, 2013
    13
    0
    This is the valve
    http://www.amazon.co.uk/gp/product/B009ZCP2SE/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
    I have a thermal solar pannels that heat my copper storage tank with a solar syhpon that I copied from Willis solar syphones, standing next to it which is the heat exchanger from the pannels.
    I wired a differental temp controller so the pump only starts when the temp is hotter in the exchanger. The problem is at night the heat disapates back through the system. So this machanical ball valve will stop the heat loss.
    I think Dodgy dave idea is good, I found this and think it will be ok.
    http://www.ebay.co.uk/itm/INTERFACE...al_Components_Supplies_ET&hash=item1e70a3e64c
    Do you agree and how to wire it.
     
  11. #12

    Expert

    Nov 30, 2010
    16,330
    6,818
    That advertisement has no mention of the current carrying abilities of the relay contacts. However, the valve needs 1/10th of an amp, easily within the abilities of that relay.
    How to wire it was given to you in post #7

    One excellent feature of the valve is that it turns off its own current draw when it has completed its movement. It then waits for a reversing voltage. Very efficient to do it that way.
     
  12. Ken888

    Thread Starter New Member

    Apr 8, 2013
    13
    0
    I got it all working now.
    Thank you for all the help.
    Ken
     
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