help my dc adapter keeps dying

Discussion in 'General Electronics Chat' started by Sred, Jun 6, 2009.

  1. Sred

    Thread Starter New Member

    Jun 6, 2009
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    This question is probably (and hopefully) very simple to answer for someone out there. I'm using a relay boards to control 10 solenoids (24VDC 40Watts Each). I have two power sources: a 12VDC 800 mA for the relay board and 1 24 VDC 400 mA for all of the solenoids. My problem is that the 24Volt adapter keeps dying. What should I do? Should I power the solenoids with two or more of these adapters? or should I get a 24 VDC adapter with higher Amps?
    thanks in advance for any help.
    Sred
     
  2. DC_Kid

    Distinguished Member

    Feb 25, 2008
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    perhaps the 24vdc adapter is getting hit with some flyback voltage from the inductor (solenoid)? try adding a 36v zener across each solenoid, see if that stops the issue.
     
  3. bertus

    Administrator

    Apr 5, 2008
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    2,344
    Hello,

    You say that the solenoid is 24 Volts 40 Watts.
    The current will be 40 / 24 = 1.667 Ampere per solenoid.
    The powersupply of 400 mA = 0.4 A will not survive this.


    Greetings,
    Bertus

    PS do you have protection diodes on the solenoids?
     
  4. Sred

    Thread Starter New Member

    Jun 6, 2009
    4
    0
    Thank you both. that answers my questions. I will seek out an adapter with higher Amps or designate several adapters to only a few solenoids at a time.

    I guess I should have them protected from the induction.
    I have some diods (1N4007) that I was going to use with 12V solenoids... will these work with the 24V solenoids?

    thanks
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The 1N4007 will work to suppres the emf created by the coils.

    Greetings,
    Bertus
     
  6. DC_Kid

    Distinguished Member

    Feb 25, 2008
    638
    9
    sorry, i meant to say use zener to ground. depending on what the solenoid is used for you might choose the zener method vs. 1N400x across.

    placing 1n400x across the inductor allows for re-circulation current, which will hold the solenoid act slower. using zener to ground will allow that energy to dump to ground (not re-circ) allowing the solenoid to act faster.

    if solenoid quikness is not of concern then just use the 4007's across each, etc.
     
  7. Sred

    Thread Starter New Member

    Jun 6, 2009
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    thanks DCkid, i actually would prefer quiker performance so I'll get some zener diodes. I'm guessing they would hook up in the same way as the 1N400x would?
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,764
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    Not really, Zeners are usually used to surpress high voltage, and go to ground. I'd go with the diode across the coil to surpress the back EMF, that is the more commond approach.
     
  9. Sred

    Thread Starter New Member

    Jun 6, 2009
    4
    0
    thanks for the advice.. that sounds more up to my speed
     
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