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Current regulator

Discussion in 'General Electronics Discussion' started by JoeS, Apr 5, 2013.

  1. JoeS

    JoeS

    6
    0
    Feb 13, 2013
    Hi,

    I want to do some electroplating. For this I will need a power supply which I can adjust the current on. I'm not particularly comfortable with building a high ampage current regulator myself and not having it catch fire etc. What I was thinking of doing is buying a couple of off the shelf fixed current regulators (for instance 20 1 amp regulators) and hooking them up in parallel with inline switches. Am I right in thinking that with this setup I could then switch on 5 of the regulators and have a constant 5 amp current irrespective of the load? (Obviously the voltage would vary.)

    Also can anyone recommend any current regulators? I've done some googling and all I can find are voltage regulators. They don't specifically have to be 1A, I could use 10 2A or even 4 5A ones.

    Thanks,

    Joe
     
  2. BobK

    BobK

    7,609
    1,648
    Jan 5, 2010
    An adjustable voltage regulator can be wired as a current regulator. See the LM317 datasheet for example.

    I am not sure about paralleling current sources. Theoretically it should work, but there might be problems. Hopefully someone more knowledgeable will chime in.

    Bob
     
  3. JoeS

    JoeS

    6
    0
    Feb 13, 2013
    Ah thank you, that would explain why I only found voltage regulators when researching current regulators.

    Joe
     
  4. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Not to discourage you from building your own, but you can get low cost used lab power supplies all over Ebay that will allow you a full range of adjustment both voltage and current and they can be had quite reasonable...
     
  5. john monks

    john monks

    693
    1
    Mar 9, 2012
    Why not use a 12 volt battery charger with a current meter and a variac?
    They are designed for supplying amperes over a long period of time and have
    a current meter and have convenient clips and have a built-in circuit breaker in case
    of short circuits. And you can always find another use for it in case you leave your
    lights on.

    Normally you do not want to use a constant current source regardless of the load
    because you might become the load and you will be no more. So you want to limit the voltage to some same level. How complicated are you willing to go? There are plenty of schematics on the web.
     
  6. JoeS

    JoeS

    6
    0
    Feb 13, 2013
    John: A variac sounds like a good idea, but would that maintain the same current even if the load changes? I'm thinking of doing some experiments with electrolysis at some point so I'd like something that is quite versatile.

    CocaCola: That sounds great, can you give me any examples please? I've researched this and haven't found any.

    Thanks,

    Joe

    EDIT: CocaCola, from what I saw on eBay there are supplies which will limit the maximum current but you still have to set it to a specific voltage. You can't just say "I don't care about the voltage just make sure it is x amps"
     
    Last edited: Apr 5, 2013
  7. JoeS

    JoeS

    6
    0
    Feb 13, 2013
    Eh?

    What I'm thinking of doing now is using a LM317 with a potentiometer to set the maximum current. The pot will have maximum resistance of 1.2 KOhms. This should allow me to adjust the current from a few milliamps up to an amp. I can them connect several of these in parallel.

    Joe
     
  8. john monks

    john monks

    693
    1
    Mar 9, 2012
    Maybe you are try this. You can connect as many LM317's together as you like as long as the output pin has some substantial resistor to that the regulators work about the same. You could juggle the 0.4ohm resistor around to your liking.

    http://img580.imageshack.us/img580/2346/zzzzev.jpg
     
    Last edited: Apr 6, 2013
  9. JoeS

    JoeS

    6
    0
    Feb 13, 2013
    Thanks, that is exactly what I'm looking for. I'll get some components and do a test.

    Joe
     
  10. BobK

    BobK

    7,609
    1,648
    Jan 5, 2010
    A 1.2K pot in the LM317 circuit would make it very difficult to adjust the current at the high end (low resistance). If you really need that kind of range of current, I think switching in different resistors (or pots) would be a better idea. Each pot should have a fixed resistor in series so that the high end is limited.

    Bob
     
  11. gregfox

    gregfox

    149
    3
    Mar 25, 2013
    heatsink

    Use a big one!
     
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