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Trying to assemble a high voltage low current PSU

Discussion in 'Power Electronics' started by Alx, Jan 18, 2019.

  1. Alx


    Jan 18, 2019

    I need a 300V DC power supply with a limited current of 0.5mA (or 500 micro ampere) for specific electrolysis work that requires high voltage and low current.

    I found sophisticated electrophoresis PSUs which are sold for thousands of euros. But since I need both limited current and voltage, I wonder if I can find a workaround.

    I am pretty much ignorant in electrics but I am trying to understand, because the other solution is off-budget for me.

    For example, I could find interesting power solutions here

    As you can see some models are delivering the much wanted micro amperes. But how could I limit the voltage and current at the desired rate ?

    As you see I am pretty much stucked at this point. Is it hopeless and should I apply to get a loan ?

    Your comments are welcome !
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    300V at 0.5mA will deliver a maximum power of 0.15W. That is well within the capabilities of something powered by batteries or a low voltage DC plugpack (wall wart).

    At a current of 0.5mA it is also unlikely to kill you (but it wouldn't feel pleasant to be shocked by it).

    The old disposable film cameras had an inverter inside them capable of generating around 300V. Replacing the flash capacitor with something smaller (to make it safer) and adding some output resistance may be sufficient. It could be powered by a D cell or similar.
    hevans1944 likes this.
  3. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Problem is the OP has stated:
    I agree this is a simple hack, but it may be beyond the capabilities of the OP. It is also now very difficult to purchase 300 V batteries, not that you are suggesting that, but when you do find some they have absolutely outrageous prices. An easier (not necessarily cheaper) solution is to snap together a series string of 33 or 34 "9V transistor radio" batteries, add a current-limiting resistor in series with the output to limit the short-circuit current to 500 μA, and get on with your electrolysis.

    Bear in mind that 300 volts from a pile of fresh series-connected "9V transistor radio" batteries is capable of delivering a dangerous and painful electrical shock. Don't ask me how I know this. But the good news is, if cheap imported (Asian) alkaline batteries are purchased, they will last for at least as long as the "shelf life" marked on the battery, usually about ten years from date of manufacture, assuming the current is limited to 500 μA. Look for bulk battery bargains at big-box home improvement stores and places like Big Lots and Odd Lots.
  4. PKiKP


    Jul 8, 2016


    May 20, 2017
    You could always try a small transformer with a diode and capacitor multiplier on the output. You could easily achieve the required O/P volts. The output current would be diminished with each stage.
    Have a look at the following link which explains it all.
    hevans1944 likes this.
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