12VDC Power Source

Discussion in 'General Electronics Chat' started by Fdam, Jul 18, 2014.

  1. Fdam

    Thread Starter New Member

    Jul 8, 2014
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    Hi folks:

    I'm looking for a power supply to have at my desk, for my arduino projects.

    I know I need a 5V supply, but a 12V supply would be good for driving large step motors or other type of loads.

    So my idea is to have a 220VAC -> 12Vdc power supply, and from there to get the 5Vdc through an DC step down regulator, and maybe a 3.3Vdc also.

    My question is:

    I have available a 12VDC - 2Amps wall power supply for like 19€, much like a phone charger, but I also have available a industrial power supply 12VDC - 2Amps for around 15€ (a Mean Well Power supply) at the shop nearby me...

    I'm inclined to buy the industrial power supply, it's cheaper, well ventilated, and I suspect much better than the wall power supply, because at least it seems that it has current protection among other things. I'll have to build a case and put some other stuff around, but it seems a better deal...:rolleyes:

    What do you guys think?
     
  2. paulktreg

    Distinguished Member

    Jun 2, 2008
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    You can pick up a decent ATX computer power supply for very little money and they make a great bench top power supply if you're just starting out.
     
  3. Fdam

    Thread Starter New Member

    Jul 8, 2014
    6
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    Hi:

    Thanks. I've thought of that, but doesn't ATX power supplys need some load to work?

    At times I'll only be drawing around 100mA's...
     
  4. paulktreg

    Distinguished Member

    Jun 2, 2008
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    Yeah some do but it always a good idea to load the +12V rail. It only needs something like a 10R 25W resistor.

    It was just a thought.
     
  5. ScottWang

    Moderator

    Aug 23, 2012
    4,853
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    You can using a LM2576-adj and adding some resistors and switch to setting the fixed voltage as 5V or 3.3V, or using a VR to adjust the voltage.

    You can also adding a LM2937-3.3 then you have the 3.3V fixed voltage and using a LM7805 then you have the 5V fixed voltage.
     
  6. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,383
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    I am sort of with Paul here. I used to have an old Apple Macintosh LC II, one day it stopped working so I took it apart and threw most stuff away, but I kept the power supply from it, it got -5 volt, +5 volt and +12 volt, I have been using it on and off for just checking stuff out. I guess modern computer psu might be a little bit more sophisticated.

    [​IMG]
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,991
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    Only the 5 volt rail needs a 10 ohm 10 watt resistor to hold 5 volts and 3.3 volts.

    If you need 12 volts, almost any load on the 12 volt rail from your project will cause the 12 volt to stabilize at 12 volts. I think the 5 volt load may be used to reference the 12 volt rail because I haven't had much problem with that. I don't need an ultra stable 12 volt. The atx spec is fairly broad definition of 12 volts so it is not perfect - even with a load.

    There are plenty of instructibles on how to do this.
     
  8. tom_s

    Member

    Jun 27, 2014
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    Last edited: Jul 20, 2014
  9. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Atx psu best option easy to convert.
     
  10. to3metalcan

    Member

    Jul 20, 2014
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    Of the two options you mentioned, definitely go for the Meanwell...with the wall supply, you're not paying for ruggedness, you're paying for miniaturization and manufacturer specificity (ie, it having the type of connector it needs to plug into something else.) Plus, a lot of times, the regulation on wall supplies is not great, and I'm saying that as someone who has hacked open his share of both linear and switching wall-warts for various purposes! :)
     
  11. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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  12. Fdam

    Thread Starter New Member

    Jul 8, 2014
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    Thanks folks for the input:

    I have an 1989/1990 2A power supply based on the L200C with a large transformer, that I'll be using for providing DC to some buck converters to step down to 5V and 12V...

    I'm building this in such a way that if needed I can remove the L200C based power supply and use 12V wall wart or the more rugged industrial Mean Well power supply.
     
  13. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    I like a 60W plastic housed brick with multiple outputs via a cord and DIN connector for this application.

    I don't like a supply with openings that staples, paper clips and drinks can enter outside the lab. I have a supply that has -12V, +5V and +12V outputs and I've made a pigtail that plugs into the supplied DIN connector and has color-coded shrouded alligator clips but I can make additional pigtails with any connectorization I need.

    Like this one: http://www.condorelectronics.net/catalog/table.php?subcat=62
     
    Last edited: Jul 27, 2014
  14. AlphaDesign888

    New Member

    Jul 27, 2014
    189
    10
    Gawd you can buy an lab power supply on eBay for next to nothing now. Dual rail tracking. Variable voltage and current limiting. Digital displays. No brainer USD 100 inc ship.
     
  15. Fdam

    Thread Starter New Member

    Jul 8, 2014
    6
    0

    Yes that right. I've seen some at around 55€, including shipment.
     
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