12v solenoid valve - hot

Discussion in 'The Projects Forum' started by John Croucher, Dec 20, 2015.

  1. John Croucher

    Thread Starter New Member

    Dec 20, 2015
    9
    1
    I have 4 solenoid valves being controlled with a raspberry pi and relay board setup.

    They are 12V DC, but I accidentally ran them on a 12V AC power supply. I noticed they were getting hot and buzzing.
    It was after looking closer I realised my mistake.

    I replaced the power supply with a 12V DC one. The buzzing went away, and I thought this would also fix the getting hot issue.
    However it didn't. They are getting hotter than before, so hot that I can not touch them.

    Is it normal for solenoid valves to get this hot? If not, does anyone know what I can look at to try and fix it?
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Are the solenoids rated for continuous use, or is a maximum duty cycle specified?
     
  3. John Croucher

    Thread Starter New Member

    Dec 20, 2015
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    They are cheap ones from eBay so there are not many details, and I can't be sure if they are even accurate.
    But these are the details listed

    • Voltage: 12V DC
    • Current: 250mA
    • Pressure: 0.02 - 0.8Mpa
    • Valve type: diaphragm (operated by Servo)
    • Operation mode: normally closed
    • Inlet and outlet: hose barbs for 1/2" (outer diameter) hose
    • Fluid temperature: 1-100 ℃
    • Material:Metal & Plastic
    • Usage: water and low viscosity fluids
     
  4. Picbuster

    Member

    Dec 2, 2013
    374
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    First off all measure the current and the connected voltage.
    If within the spec's 10% approx. if not.
    connect the valve to a adjustable dc power supply and turn the voltage up till valve goes open.
    Read the voltage and measure temp.
    But heat can also occur when the voltage is to low to open valve ( eq 24V valve @ 18V)
    What to do when all fails and still hot? open the window and offer the valve a free val.
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    = 4Watts, & will feel quite hot to the touch...
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Do you have a link to the supplier?
    They should not be too hot to touch.
    Max.
     
  7. strantor

    AAC Fanatic!

    Oct 3, 2010
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    sounds to me like it isn't a solenoid valve. Sounds like it's probably (using the word "servo" loosely as a chinese ebayer would) a motorized valve. The kind you would apply voltage for a moment to open it and then remove voltage and it stays open. Then apply reverse polarity for a moment to close it and it stays closed.
     
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  8. John Croucher

    Thread Starter New Member

    Dec 20, 2015
    9
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    Just an eBay link.

    http://www.ebay.com.au/itm/262079295580

    There are many people selling the same ones.

    These ones are closed without power, and open with power. A soon as the power is removed they snap closed.

    I will try the suggestion of reducing the supply voltage to a level where it still opens to see if that helps.
     
  9. paulktreg

    Distinguished Member

    Jun 2, 2008
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    They are continuously rated at 4.8W so they will probably get hot.

    A crude way to drop the current is to put a large electrolytic capacitor with parallel resistor in series with the soleniod rather like this.
     
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  10. John Croucher

    Thread Starter New Member

    Dec 20, 2015
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    Thats an awesome idea.
     
  11. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    They are likely not too hot and well within their rating. I wouldn't worry about it...
     
  12. John Croucher

    Thread Starter New Member

    Dec 20, 2015
    9
    1

    Just did a test. It turns on at 9v, i can then turn the voltage back to 4v before it switches back off.
    At full 12v it uses 0.4 amp.
     
  13. John Croucher

    Thread Starter New Member

    Dec 20, 2015
    9
    1
    Just measured the temperature when running at 12v. It seems to peak around 80c ( 176f ).
     
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