Wall Warts

Discussion in 'General Electronics Chat' started by wdkh68, May 6, 2010.

  1. wdkh68

    Thread Starter New Member

    Jan 12, 2010
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    Is there any advantage of using a AC-DC switching vs transformer (linear)wall wart? Of course, the switching one is much smaller and lighter weight per rating, but costs more. I will use these for powering various LED projects along with 78xx regulators and filter caps. Thanks!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Your LED's wont mind any residual noise that a switcher might leave in its output, so the main criterion might be finding the wart that has some capacity that is a bit greater than your projected load.
     
  3. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    The switcher types usually have a regulated output. The simple transformer only types usually have a large variation in output voltage depending on load. So if you use a switcher type, you might not need a 78xx regulator if you can find a wart that already puts out the voltage you need.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    The switchers, in addition to being regulated, also tend to put out more current than regular unit per weight by a large margin. With applications where noise is not an issue this is a real bonus, and even with sensitive applications it isn't that hard to filter the DC.

    Overall I think very highly of them.
     
  5. wdkh68

    Thread Starter New Member

    Jan 12, 2010
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    Thanks guys! I have a 100-240v. 50-60hz 12vdc 1.0 amp switcher wall wart that I am using on a LED sequencing circuit, but it does not work properly unless I put a .33uf or a .01uf cap across the 12v wart output. Why is this?
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Something that wasn't mentioned as a disadvantage, many wall warts assume a certain loading. You must have the minimum load or they don't work as predicted.
     
  7. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    I said "The simple transformer only types usually have a large variation in output voltage depending on load.". I didn't explicitly say that it is a disadvantage; I left that up to the reader to figure out.

    On the other hand, I haven't seen any switcher types that malfunctioned without a load. I wonder if there's something wrong with the one the OP is using?
     
    Last edited: May 7, 2010
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