Constant current regulator

Discussion in 'The Projects Forum' started by power453c, Nov 17, 2011.

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  1. power453c

    Thread Starter New Member

    Nov 17, 2011
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    Hello all,
    New to this forum, so I say howdy.

    I am looking for a nice simple and easy design, for a current regulator.

    I need it to output 14vdc at 20 amps.

    The trick is I don't want it to shut down when the 20 amps is reached, I want it to continue providing the full 20 amps but no more. Also variable current under the max amperage is needed based on load.

    Please Help a newbie.
    Robert
     
  2. kender

    Senior Member

    Jan 17, 2007
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    Hi Robert,

    Are you trying to build a purely constant current (CC), or a constant voltage constant current (CCCV) circuit? Is it acceptable if your voltage is not exactly 14vdc, while the current is spot-on 20A?

    For example, here's an OpAmp based constant current (CC) circuit:http://www.ecircuitcenter.com/circuits/curr_src1/curr_src1.htm Multiple transistors can be hooked up in parallel to handle larger current. Notice that the load is not grounded. Notice that it doesn't regulate voltage.

    - Nick
     
    Last edited: Nov 17, 2011
  3. SgtWookie

    Expert

    Jul 17, 2007
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    It won't be simple, nor will it be cheap, and certainly not easy.

    If you want a linear regulator, which might be easier to build, you'll need a transformer that'll weigh in the neighborhood of 15-20lbs, large rectifiers and very large filter capacitors, a bunch of power transistors for the output drivers, and some really large heat sinks that are fan cooled. It will make a great heater for your garage. You'll get dizzy watching the electric meter spin.

    If you want a switching supply; that would be a heck of a lot more efficient. However, now you are talking about a rather complex system. Unless you have at least intermediate-level skills in electronics, you will be very, very lost.

    Your best solution would be to buy an off-the-shelf supply that meets your needs. There are lots of different supplies that are available, and you will be able to buy one for about the same investment as you would if you built an efficient one - but you would have it a whole lot sooner.
     
  4. power453c

    Thread Starter New Member

    Nov 17, 2011
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    I appreciate your quick responses. Voltage regulation is not required, this will be an automotive circuit. I just don't need the load to draw more than the system can handle but keep running when the maximum current draw is reached.
     
  5. power453c

    Thread Starter New Member

    Nov 17, 2011
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    Hello kender,
    I was reading that page you sent,very informative. Just one question do you think it is possible to use a mosfet instead of a transistor?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    And with that statement, we'll have to mention the Terms of Service, a portion of which I'll quote:

    Since you're planning on using it in a vehicle, that means you're planning on making a modification to the automobile. There are only three things that come to mind that you would want to use a current-limited supply for in an auto, and the first two don't count; however it reflects back to the line above the "Automotive modifications" in paragraph 6, above.

    It's one thing to repair a vehicle so that it will once again perform within factory specifications. Modifying a vehicle is a completely different and broad subject, and one we no longer entertain discussion about for various reasons - but the primary one is safety.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    And on that note ...

    The All About Circuits forum Administrative Team has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

    This thread is against the AAC forum rules, Chapter 6, as seen here:

    http://www.allaboutcircuits.com/l_tos.html


    Automotive modifications of any kind are strictly forbidden. Therefore, this thread will be closed.

    Please try to understand the reasons behind this action, and feel free to browse and use the forums.

    You might find answers to your questions in one of these forums:

    http://forum.allaboutcircuits.com/sh...ad.php?t=54400
     
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