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Favorite bench supply circuit?

Discussion in 'Electronic Design' started by Usual Suspect, Mar 5, 2007.

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  1. I want to build a bench power supply, and am looking 'round the net for a
    good circuit.

    Requirements: 2 outputs, adjustable v, adjustable i, v & i meters (or
    digits). Prefer 30v max, or similar. Preset v selections (5, 12, 15, etc.)
    would be nice.

    Here's one I found, complete with the designer's smiling face on each circuit

    What's your favorite circuit? Features you like that I haven't mentioned?

  2. D from BC

    D from BC Guest

    Most often my prototypes include a power supply...
    I seldom use my homebrew power supplies.
    Also, when I do need a power supply it's usually some punk voltage
    like 54V at 3amps.
    Better to put time into unique projects and buy a power supply.
    D from BC
  3. Guest

    I couldn't agree more. There are so many used supplies that it isn't
    worth the effort to build a bench supply. Just the damn box and a heat
    sink will be about $20, which is what I pay for bench supplies.
  4. sez:
  5. DaveM

    DaveM Guest

    Perhaps you should get a copy of the current issue (March 2007) of Nuts & Volts
    magazine. It has a construction article that's just begging for you to look at
    it. The article is "A Test Bench Power Supply". The power supply, as
    presented, provides two 0-20V @ 1A supplies and one fixed +5V @ 1A supply. Your
    other fixed supplies are easily added by using the appropriate power
    transformers and regulators. The regulator circuits are trivial.
    They will send you a free copy to entice you to become a subscriber. (My own
    subscription has been ongoing since 1/80)
    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

    Some days you're the dog, some days the hydrant.
  6. miken

    miken Guest

    Saw in that web-site this statement

    ".....the notorious LM723 , a versatile but rather unfriendly IC...."

    Can someone please tell me about the unfriendly side of this IC.

    I just bought 50.

    Thanks de miken
  7. While not wanting to put you off, unless you already have most of the
    major parts it will cost you far more to make than to buy a ready made
    one. Such is life these days.
  8. seanacais

    seanacais Guest

    Here is a simple one for 0-30V @ 3A with current limiting

    If you read thru the forums you'll find a parts list and updated
    schematic that expanded this to dual 0-30 @ 5A complete
    with PCB's that can be downloaded.

    Further reading will show how to add digital V and A meters.

    Good luck

  9. Rich Grise

    Rich Grise Guest

    It looks like a lot of fun, actually. To make it really sexy, you should
    check the LM317 data sheet, and modify this one to be adjustable down to
    0. :) A current limit wouldn't hurt, and I guess you can do whatever
    metering you want to.

    I do kinda like the idea of presets - I even already have a circuit
    in mind for n latching circuits for n spst switches. :)

    Have Fun!
  10. Rich Grise

    Rich Grise Guest

    Too Many Leads. ;-)

    It also could be persnickety about input and output cap. values, but
    that's just a WAG.

  11. TimPerry

    TimPerry Guest

    ok as far as it goes but you need to specify a current, line regulation,
    load regulation, curent limiting, crowbar protection,
    switching or linear, and even line voltage. also voltage range i.e. 0-30
    5 - 30 etc.
    my favorite? that would be 7 or 8 200w or larger NPN transistors in parallel
    with emitter resistors mounted on a huge heatsink driven by another 200 W
    transistor powered by a very large transformer into matched 30A bridge
    the main filer cap is a very large "computer" cap (ok, if you are young
    think of a "power stiffener" for car audio.)

    the voltmeter is a large mirrored scale and "expanded" using switchable
    precision zeners. i.e. 0-10, 10-20, 20 -30V
    the ammeter is a matching large mirrored scale attached to a high current
    meter shunt through a multi-turn calibration pot. the meter has diode
    limiters to protect it from surges.

    the supply can be driven from an internal or external reference. the
    reference source is on a separate winding and is offset several volts below
    common so as to achieve a zero volt output. for improved load regulation the
    regulator references to the output terminals. voltage is controlled via a
    multi-turn pot.

    primarily intended for high current applications at 13.8 Vdc this unit was
    result after many less robust supplies became shall we say... non
  12. Guest

    Electronics (ham) swap meets. Any used HP is fine. Some of the Lambda
    late model supplies with digital readouts have problems, but the older
    gear is good. None of mine have digital displays, but meters are
    cheap. I even have one of the HP Harrison supplies, which are stone
    age. Speak of the devil:
    This this the Lamba that often has trouble:

    Bench supplies are quite heavy. I'd sure hate to buy one on ebay
    unless the seller double packs it. Still, I'd get a HP supply from
    Ebay before building my own.

    Speaking of supplies with digital readouts, I recall a chip I designed
    that worked fine with any bench supply except those HP with the
    readout. [I'd have to research to find the number.] It turns out HP
    put in a nice soft start feature that was so "soft" it found a flaw in
    my undervoltage lockout.
  13. SparkyGuy

    SparkyGuy Guest

  14. THERES RAJ, BLR sez:
    You, sir, are a troll.

    The site is nothing but one of those "faux" resource sites that crop up way
    too often in Google results stating that they have [fill in whatever terms
    you used in your Google search] at the right price. Sites like this must be
    simply collecting hits, showing the numbers to potential advertisers, and
    collecting $$.

    If anybody has any other suggestion as to what purpose these
    serious-waste-of-time sites serve, I'd be happy to hear.

  15. N Cook

    N Cook Guest

    Assuming your 2 supplies are from isolated secondaries or separate mains
    transformers and the outputs will parallel, then series/isolated
    pair/parallel switch is easy to add to double volts or current range (single
    If for repair or soak testing then something I would have had a use for is a
    presettable current monitor that sounds a sounder if the current drain goes
    above or below a settable amount from the initial free, ie below any current
    limit , current drain, for instability/thermal/intermittant fault checks
  16. cr500r

    cr500r Guest

  17. cr500r

    cr500r Guest

    They can be a bit noisy (understatement), but PC supplies are shielded, the
    regulation is usually really good, and the amperage is great, as well as the
    efficiency compared to linear.
    It all depends on how much radiated noise you can accept, you can always
    filter the wires coming out of it.
  18. Guest

    Guest Guest

    yep, older hp,harrison bricks!

    an hp6200b has been my companion for YEARS!

    analog meter, basic controls, two plug terminals front, all sorts of useless
    terms on the rear too!

    stay with a basic type, no frills that will distract u from the task at
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