Can anyone recommend an idiotproof design for a big variable current regulator?

Discussion in 'General Electronics Chat' started by spasticteapot, Nov 14, 2009.

  1. spasticteapot

    Thread Starter New Member

    Nov 14, 2009
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    I'm looking for a simple schematic for a relatively beefy variable current regulator capable of supplying five or more amps (preferably ten) at twelve volts. This will be for an electroplating setup, so high efficiency, low noise, and high precision are not required - I'm looking for something simple and cheap.

    Any recommendations?
     
  2. k7elp60

    Senior Member

    Nov 4, 2008
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    Use a LM338K with an variable resistor or with switchable resistors. See figure 19 of the attached file. Change the resistor for the selected current.
     
  3. spasticteapot

    Thread Starter New Member

    Nov 14, 2009
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    The problem with this design is the requirement for a low-current high-power rheostat - all the ones I've found are quite expensive. Is there a more reasonably priced option?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Yes, use a 12v auto battery charger rated for 5A.
     
  5. Papabravo

    Expert

    Feb 24, 2006
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    As a tecnical requirement "idiotproof", does not exactly reek with precision. I would be interested in any elaboration you can offer for this particular requiremnt, especially as it relates to existing equipment with which you may have any specific experience.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Something really simple might be a rotary selector switch or a series of toggle switches which connects various size automotive-type incandescent lamps from the +V supply to the load.

    Automotive lamps are available in a wide variety of sizes/wattages. A trip to an auto junkyard (for the UK crowd, the breakers) could provide a wide variety of auto lamps with sockets and pigtails (wires) already attached.

    A quick search on the Internet would give the wattage rating for the lamps.
     
  7. spasticteapot

    Thread Starter New Member

    Nov 14, 2009
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    I don't own an oscilloscope, making diagnostics of switched-mode power supplies very difficult. Idiotproof might be too strong a word, but I'd prefer something that doesn't have several dozen components.

    I should specify that I'm looking for something that can maintain a preset voltage, not simply a rheostat. The impedance of a plating setup can vary during the plating process, and too much current can cause big problems.
     
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Last edited: Nov 15, 2009
  9. k7elp60

    Senior Member

    Nov 4, 2008
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    Here is a circuit I built a number of years ago to discharge batteries at a constant current. It is adjustable from a few Ma to about 10 amps. I modified the circuit so that the 12V power supply supplies the current.
    The post adjusts the current and the op amp keeps it constant. The transistor was mounted on a big heat sink.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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  11. k7elp60

    Senior Member

    Nov 4, 2008
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    Thanks SgtWookie for the information.
    When I built the circuit I worked for an electronic distributor and the my cost was not very much. I built the circuit over 10 years ago.
     
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