power supplies to build or buy

Discussion in 'General Electronics Chat' started by dthx, Jun 15, 2013.

  1. dthx

    Thread Starter Member

    May 2, 2013
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    When I start experimenting on the breadboard...
    Im setting aside a table, getting a meter, etc...
    I have in my mind a thought that it might be cool to have the ability to be able to generate different voltages .....
    Say....1vdc to 12vdc.....
    1.) is that a good idea ?
    2.) is it cheaper to build a power supply that does that or buy one?
    Using something youve built is to my mind cooler than buying something...
    What say all of you...?
     
  2. bug13

    Well-Known Member

    Feb 13, 2012
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    1) I think it's a very good idea.
    2) I have done both, building one is fun if you haven't already, but after building my first one, I would prefer buying one, it's a lot easier and better.
     
  3. RobeeJ

    New Member

    Mar 19, 2013
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    Speaking as a total amateur, building one is great, especially if you design it yourself and adapt it as you go. So simple basic unregulated design first, then voltage regulator next, and then adding V+A meters to it, current regulation, digital control, and so on, and so on.

    BUT, if you want to do other things at the same time, and you can't because you are still building your PSU to power it all, buying one is good. :)
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    If you ambitious you can modify an old ATX to variable output 2V to 28V, i can give you a link to my site to show you.
     
  5. Shagas

    Active Member

    May 13, 2013
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    Please do , I'll be converting a PC CPU into a bench power supply in a few weeks so i'm interested in what you did
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Dodgydave

    Depends on which chip you have in the atx, let me know
     
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  7. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    I don't speak for everyone but me I just bought one on Ebay for about $50 bucks (MASTECH DC POWER SUPPLY HY3003D)... I was finding all kinds schematics to build one but found out that they don't have any real safety features.. So I just bought one because it's less likely to burn down my house ,But right now I am working a really small voltage power supply with voltage display for a breadboard ...










    Here Check this out ..
    http://dangerousprototypes.com/2012/06/28/new-prototype-atx-breakout-board/
     
    Last edited: Jun 15, 2013
  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Actually a very good point. A bench supply will be your friend for life: they are very hard to kill (though I've killed some) so they will survive much abuse from your circuits going bad, they can help protect your circuit form your mistakes (current limiting), and they have every voltage possible from zero to their max.

    I would *never* use a computer power supply to power my circuits. While it does provide some nice stable voltages it does so with enough unlimited current for you to put your eye out.

    I had a boss once who insisted I use a battery to power development units... until the day there was a short and the board went up in flames (literally). A current limited supply would not make that happen... a computer supply will do it's best to get a fire going.
     
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  9. studiot

    AAC Fanatic!

    Nov 9, 2007
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    If you are seriously building up your experimental electronics knowledge I recommend getting one of the books by Michael Tooley. They really are first class.

    In particular the 1990 edition of Electronic Circuits is designed to teach about components and circuit configurations by experiment. It is all superbly explained.

    You build up a series of modules

    AC power supply
    Fixed DC power supply
    Variable DC power supply
    Digital panel meter
    Transistor tester
    Digital ohmeter
    Function generator
    Pulse generator
    Output stage
    Crystal Calibrator

    and learn a great deal in the process.
     
    Last edited: Jun 15, 2013
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  10. Shagas

    Active Member

    May 13, 2013
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    Isn't there this thing called a 'Fuse' that prevents our circuits from blowing up in case of a short or overcurrent?
     
  11. Shagas

    Active Member

    May 13, 2013
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    I checked out the name . Any books in particular that you would reccomend?
     
  12. studiot

    AAC Fanatic!

    Nov 9, 2007
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    There are two Tooley brothers who have written some good stuff for magazines plus several books together. IHMO they are much better than the Penfold offerings.

    The book I recommended ( Electronics Circuits ) has been renamed in recent editions and I'm not sure if it has quite the same format.

    My old copy was ISBN 0 434 91968 3

    Incidentally fuses are fine to protect electrical equipment, but are several order of magnitude too slow to protect electronic kit.

    The best sort of protection is called 'foldback' as it does more than limit the current, it actually reduces it above a certain level.

    A contined fault condition is protected against by a 'crowbar' circuit', which protects the actual power supply components, rather than the load.
     
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  13. Shagas

    Active Member

    May 13, 2013
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    Hmm but even an ordinary fast blow fuse will protect from smoke and fire won't it ? Even if the components will fry there won't be current supplied for long enough to induce a fire or anything of that sort no?
     
  14. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    Doesn't the crowbar circuit require a certain amount of voltage in order for it to work properly???
     
  15. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Sure is. It's best used for field failures, unless you happen to own an infinite stock of these components.

    A current limited lab supply is a standard piece of development equipment. I own several, each with multiple outputs.

    I suggest anyone who is serious and can afford these get some.
     
  16. studiot

    AAC Fanatic!

    Nov 9, 2007
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    The purpose of a crowbar circuit is to rapidly divert excess current from the load through another path until a fuse ruptures or breaker trips, thus isolating the fault condition until it can be properly fixed.

    Yes this takes voltage until the disconnection, at which point there is no voltage.

    The crowbar itself may be sacrificial and is often a thryristor.
     
  17. dthx

    Thread Starter Member

    May 2, 2013
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    Dave...I got your PM ......thank you very much.
    Enjoyed your other videos also...
    You guys never let me down...
    I think I'll file this for the future and stay with the "store bought" version for now....
    Many thanks
    D.
     
  18. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    Basic Bench Top Power Supplies

    Power supplies are about the only thing left that is economical to build, especially with a high current high voltage wall wart (such as is used in laptops).

    I did buy this one,

    [​IMG]

    Even with current limiting you have to be careful, as the caps filtering the output will pop an LED. To feed a good constant current source start with the outputs shorted.

    http://www.vellemanusa.com/products/view/?id=522797
     
  19. Stuntman

    Active Member

    Mar 28, 2011
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    I'm going to have to side with the current limiting crew.

    I feel like even this unit for $89 (http://www.circuitspecialists.com/csi5003xe.html) will pay for itself in headaches and parts if it saves you but a few boards from getting zapped.

    I do still have an old ATX with a 3.3 rail I may still use for a voltage source at the bench, but I'll be back to the current limiting variable for development.
     
  20. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
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    Check out mastech power supplies ...
    They are made in china ,but are pretty cheap to buy and really not bad made ..
     
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