Simple solenoid circuit

Discussion in 'The Projects Forum' started by jwarnett, Dec 1, 2010.

  1. jwarnett

    Thread Starter New Member

    Dec 1, 2010
    2
    0
    Hey

    I am trying to build a very simple circuit that will switch on and off four solenoid valves. The valves that I am using can be found at the following link

    http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0168197

    I thought it would be as simple as running a 24V supply, with each solenoid connected in parallel, and each solenoid connected to a switch, so each one can be switched individually. Also there is a diode connected in parallel around each solenoid to deal with the negative emf that can be generated. But this circuit doesn't want to work! Doesn't seem as simple as what I have first thought.

    I did electronics 7 years ago, and now have forgotten everything. So I really need some help! So could someone help me with a circuit design that will enable me to turn each solenoid on and off individually. I know it must be something simple which I have missed.

    Thanks

    Jay
     
  2. wayneh

    Expert

    Sep 9, 2010
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    It would help to post your circuit, or a picture. Are you sure your 24v supply is holding its voltage under load? Maybe it doesn't have enough juice to throw the solenoid.
     
  3. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    605
    24
    I also suggest you post a circuit. As far as PSU not having enough juice these solenoids are pretty small. 4.5W at 24V is now a lot of current. Thats 190mA. We used something similar in one of our projects and found that you had to ground the case as well. I am not sure about these ones.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Can you make one valve work from your power supply?

    Try that, and depending on the results, we can work from there.
     
  5. John P

    AAC Fanatic!

    Oct 14, 2008
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    Are the diodes the right way around?
     
  6. hgmjr

    Moderator

    Jan 28, 2005
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    I am not sure which diodes you are referring to.

    hgmjr
     
  7. John P

    AAC Fanatic!

    Oct 14, 2008
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    That's where he said "Also there is a diode connected in parallel around each solenoid to deal with the negative emf that can be generated."

    That diode should be wired so when the solenoid is powered, it doesn't conduct. If it's installed backward, it becomes a near-short that will carry a lot more current than the solenoid would. Depending on the circumstances, the result could be destroying the diode, destroying the switch that controls the solenoid, destroying the power supply, or (this one matches the symptoms) pulling down the voltage on the power supply so that the circuit no longer functions. If that happens, it would seem as if nothing works. Of course, if the power supply is dead, that would look the same.
     
  8. whatsthatsmell

    Active Member

    Oct 9, 2009
    102
    4
    This may sound like an inane question, but are you sure the 24v power supply you are using is DC?

    24v AC supplies are quite common.
     
  9. wayneh

    Expert

    Sep 9, 2010
    12,100
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    Much moreso than 24v DC supplies, I think! This would produce results similar to having the diodes in backwards. No worky.
     
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