Bench supply with current limiting

This is a bench power supply with adjustable voltage and current limiting. [Sylvain's] creation can regulate 0-25 volts while sourcing 0-5 amps. Current limiting is a nice feature as it will allow you to test your prototypes to ensure the power regulator you choose will not be over or underpowered.

This supply is really a two-in-one. The case has two separate circuits so that you can have different power rails going at the same time. There is a microcontroller involved, but the ATmega32 doesn’t do anything more than measure the voltage and amperage and drive the graphic LCD screen. Two potentiometers are responsible for setting the voltage and limiting the current.

[Thanks Sargonout]

Comments

  1. willy says:

    Instead of using hooking up a transformer, could you just cheat and use an old PSU?
    The one i use for my electronics stuff says it can supply 12v 14A, and a -12v 1A (among others of course)… You could use those to get 24v, i’m guessing you’d want to limit the Amps though…

  2. Erik Johnson says:

    @willy sometimes I want a specific voltage that stock PSU won’t output. I may want to drive some components directly (e.g. LED) without any of the usual supporting voltage drop/current limiting parts (resistors, secondary regulators)
    Or I may want to control the variables on the fly and find my thresholds before things go to smoke…

    Nice project, I wonder how much of that empty space he can get rid of and not have any heat issues

  3. Haku says:

    That’s a really nice project, it’s extremely handy to have a bench PSU that you can set the voltage & ampage outputs, which is why when I bought one I spent extra to get digital control (just punch in the number), just a shame I didn’t have enough to get one which shows more decimal places on the amps and subsequent watts display.

    Seeing as the display is user programmed, one addition I’d make to it would be the ability to show watts.

  4. bogdan says:

    I like your design. I am working(actually thinking) from time to time about building one such power supply. I know the original design, and I do want to make it digital.
    But most of all I want to make it scalable in voltage and current without needing high voltage opamps.
    The way to avoid this, both in your design and the one I am working on is to use transistors controlled by the opamps to sink the current from Q5 on your schematic. I’ve used a P channel mosfet and changed some other parts of the circuit.

  5. ReKlipz says:

    Neat! Makes me want to get back to work on my adjustable switch-mode bench supply (was dabbling with active PFC, although I know that it’s probably overkill).

  6. bilbao bob says:

    I had a very cool HP constant current/constant voltage power supply that actually worked all the way down to zero – most can’t get below .7v without going ape. The HP could get to .07v and still use current limiting.

    Stock PSUs can’t easily be hacked to do this – it requires pretty sophisticated electronics. You pretty much get voltage or current, but not both.

    In biology land, you can build pretty impressive isolated variable supplies using tiny watch batteries. It’s useful when you want to stimulate nerve cells without damaging them from accumulated bias voltage issues.

  7. onlinepharmacy says:

    you’re a pretty cool guy, aren’t you bilbao bob

  8. Tachikoma says:

    “Current limiting is a nice feature as it will allow you to test your prototypes to ensure [that your breadoard does not go up in flames when you screw up].”

  9. saimhe says:

    Is the firmware version so important that it must be always displayed?

    Never saw such a thing in a professional product.

  10. Dave McDave says:

    @ bilbao bob: I find your posts more interesting than most of the hacks on this site.

  11. Myke says:

    This device is converting a ton of energy into heat.
    You could at least have a relay or an SCR to switch between different topologies.
    Also, you are converting 43V to 32V and that to 5V with linear voltage regulators. Do you realize that converting 43V to 5V actually means that you have a 12% efficiency?

  12. Drone says:

    @Myke, Sometimes you need a really clean supply. This all linear supply might fit the bill; a switcher would be far more efficient but far more complex (if not impossible) when trying to achieve the same performance.

    I agree with you however, I would have dropped in a separate transformer for the low voltage. Cheap little wall-wart transformers may do fine.

  13. Myke says:

    Far more complex, impossible? Are you serious?

  14. Syd Kahn says:

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