Connect with us

24v Solenoid - AC vs DC

Discussion in 'General Electronics Discussion' started by Ben Halicki, Sep 20, 2015.

Scroll to continue with content
  1. Ben Halicki

    Ben Halicki

    10
    1
    Sep 3, 2015
    Hi guys,

    Sorry if this has been asked thousands of times over, but I haven't been able to find a definitive answer (that I understand!).

    I have a programmable logic controller that requires 24V DC. I want it to drive 24VAC solenoids, but I don't really want to have another AC power supply just for the solenoids.

    Can someone please explain what the difference between an AC and a DC solenoid is? From what i understand, it is just a coil. If I measure the current draw on 24VAC, it is around 30mA, if I make sure it is drawing no more than 30mA on 24VDC, will it eventually damage the solenoid?

    Thanks in advance,

    Ben.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,880
    2,094
    Nov 17, 2011
    An AC coil will probably work on DC, not vice versa. With DC you may have to add a series resistor to limit the current.
    When using a DC coil with AC, the magnetization may not be high enough to activate the expected operation (e.g. movin a relay contact). AC coils typically use a shader ring to keeep the magnetic field up during the zero crossing of the AC current.

    Here's some interesting material.
     
    Ben Halicki and duke37 like this.
  3. Old Steve

    Old Steve

    734
    169
    Jul 23, 2015
    Using DC, you'll need a different voltage than when the coil is powered from AC. I didn't know the answer originally, so did a quick Google. (Did you try that before asking?)
    See here:-
    http://ecmweb.com/content/using-ac-coils-dc-power

    And a bit more general info, a comparison, here:-
    http://www.ledex.com/solenoid-applications/ac-vs-dc-solenoids.html

    These are the full search results:-
    https://www.google.com/search?q=difference+between+ac+and+dc+solenoid+coils&ie=utf-8&oe=utf-8

    Can't you tap the AC from immediately before the rectifier in your 24VDC power supply, then control a relay using 24VDC to switch the 24VAC to the solenoids?
     
    Ben Halicki likes this.
  4. Old Steve

    Old Steve

    734
    169
    Jul 23, 2015
    Sorry Harald, I was typing at the same time. We linked to the same document, too. :oops:
    (I removed that one from my post.)
     
    Ben Halicki likes this.
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    9,880
    2,094
    Nov 17, 2011
    No need to be sorry, Steve. This happens. It's a good sign the answer can't be too absurd :D
     
    Ben Halicki and Old Steve like this.
  6. Minder

    Minder

    2,948
    623
    Apr 24, 2015
    If you have a linear type 24vdc supply right now, you could come direct off of the transformer secondary, you just need a blocking rectifier between it and the capacitor.
    Or simply a 240v/24v transformer.
    The resistance of an AC inductive device is very low, it requires the inductive reactance effect (AC) to limit the current.
    What is the nature of the PLC outputs, if relay outputs switching can be AC or DC.
    The only advantage to AC solenoids is they energize a little faster than DC, but after that DC are the better choice.
    M.
     
    Ben Halicki likes this.
  7. Ben Halicki

    Ben Halicki

    10
    1
    Sep 3, 2015
    Thanks for the replies and links guys, some very useful information there. I had tried googling, but was lost when the posts started talking about inductance of AC vs DC. Not something I really understand yet. The power supply is a 240VAC to 24VDC switchmode, which makes it difficult to tap into (for me anyway...).
     
    Old Steve likes this.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-