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Choosing the Right Power Supply — Parallax Forums

Choosing the Right Power Supply

SRLMSRLM Posts: 5,045
edited 2009-01-11 05:03 in General Discussion
Hi,

I'm considering buying a power supply for personal use, and I was wondering what sort of recommendations anybody might have. I've found that I can have one new piece of test equipment, and the power supply has beat out a soldering iron, oscilloscope, function generator, and desoldering iron. So, for my supply, I would like something that works with about 3 to 16 volts, up to about ~20 amps (for large motors). The smoother the output (lower ripple?) the better. As for cost, something less than about $350 would be good, especially if I can use it for years to come. Any suggestions? Perhaps a respected manufacturer or two?

Comments

  • RickBRickB Posts: 395
    edited 2009-01-05 04:47
    Given your differing requirements I would vote for 2 supplies. 1 with 0 to 20-30 volts at 2-4 amps with very good regulation, .01% or better and 1 with minimal regulation, 6-20 volts for the motors. Even an unregulated supply with a variac would work for the motors. A regulated linear supply at that current is spendy. The only bad thing about an unregulated supply at that current is the lack of a current limit. Wires and traces tend to vaporize when shorts occur. Even a 20 amp unregulated supply could supply much more than that for 10's of milliseconds. Ebay is your best bet. Shipping cost will be painful for the big one.

    Rick
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2009-01-06 02:31
    SRLM

    Here is something that·I have done before

    LM338k will handle 5 amps

    If you can sill find these

    LM396 or LM196 can handle 10 amp

    I have set·LM338k···up for 5 amp current mode and they work very well but you have to use a heavy Heat Sink

    with them

    I did a quick search on Google for a 20 Regulator and did not find any

    ·Now you can use· bypass transistor whit a LM338k and get 20 amps output

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them

    ·
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    Sam

    Post Edited (sam_sam_sam) : 1/6/2009 2:39:20 AM GMT
  • kwinnkwinn Posts: 8,697
    edited 2009-01-06 03:54
    Why not start with the attached schematic, update the design to use the best new regulator IC's and build your own. If you are interested there is a trick to keep the power dissipation reasonable even with linear regulation of the 24/30 volt supply.
  • SRLMSRLM Posts: 5,045
    edited 2009-01-06 04:14
    Thanks for the replies so far.

    I think I'll probably stay away from making my own, for several reasons:

    1. The electricity involved can kill if I'm not careful (120 VAC)
    2. The power supply would have to be either a) constant voltage or b) variable voltage with probably poor regulation/temperature compensation
    3. It won't have a nice display that concurrently displays both voltage and amps

    I'm not really an electrical engineer (more computer science), so the power supply is to help me get the hardware working so I can go code. I don't want to worry about having to troubleshoot both my power supply and my robots. However, I'll keep the suggestions in mind if I need to construct a permanent power supply for some project.

    Anyway, here is a power supply that I found and think will work well. Any comments?


    Edit: Hmmm. Looked again at the listing, and found it was for 110 volt AC, not the 120 v AC that I need here in the US (I don't live in Brazil or Belize), so it won't work. Back to the search engine.

    Post Edited (SRLM) : 1/6/2009 4:19:58 AM GMT
  • kwinnkwinn Posts: 8,697
    edited 2009-01-06 04:19
    Specs look really good, especially at that price.
  • PhilldapillPhilldapill Posts: 1,283
    edited 2009-01-06 05:01
    Uhhhh SRLM, I'm pretty sure 110VAC devices work just fine on 120VAC. virtually any device is designed to work with the large voltage swings on the grid. Sometimes the voltage here is 140VAC, sometimes 105... There really is alot of variance and most devices handle this just fine.
  • Nick McClickNick McClick Posts: 1,003
    edited 2009-01-06 21:14
    Yeah, I think you'll be just fine with 110. I bet your outlet is ±10V, anyway. A power supply would be my next purchase, too - before an oscope or function generator. Yes, it's ripple.

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  • SRLMSRLM Posts: 5,045
    edited 2009-01-11 02:15
    As much as I have been reassured (by several sources) that a 110 VAC device can work on a 120 VAC line, I don't want my power supply to overheat and burn down my dorm... So, I've continued looking around and have found a that there is a type of power supply that you can program. Imagine that! Anyway, this one is 1-20V and 0-10 amps, switching. Any comments? Seems like a good price and fairly good specs.

    B&K Precision 1696
  • kwinnkwinn Posts: 8,697
    edited 2009-01-11 05:03
    That is also a good supply, but there is no reason the first supply would not work. AC line voltage in North America is a "nominal" 120V. I have serviced equipment rated at 110, 115, 120, and 125V in locations where the voltage has ranged from 98V to 145V without problems. All of the equipment is designed with that variation taken into account.
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