-5V to 12V Four Terminal Power Supply Involving an Adjustable Regulator

Discussion in 'The Projects Forum' started by ClimateController, Dec 23, 2012.

  1. ClimateController

    Thread Starter New Member

    Dec 23, 2012
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    I have been asked to make a four terminal power supply that goes from -5V to 12V.

    . Terminal 1 goes from 0 to 5V.
    . Terminal 2 goes from 0 to -5V.
    . Terminal 3 goes from 0 to 12V.
    . Terminal 4 goes from 0 to -12V.

    I simulated the circuit on Multisim and although there are some things that seem to have worked out on their own and feel like an accident, it seems to be working fine. There are the occasional convergence errors but the power supply is working fine. However, I can't figure out how to make the increments in voltage more uniform. Varying the resistance on the potentiometer leads to abnormal jumps in voltage. I would really appreciate it if you guys could have a look at the schematic and tell me what is wrong. Also, feel free to suggest any changes to the design you feel are necessary. Thanks.

    [​IMG]

    Here's the Multisim file. Please have a look: http://www.mediafire.com/?qisz44ze9o0o3y7
     
    Last edited: Dec 23, 2012
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Because you need fixed resistors between Vout and Adjust, then a variable resistor from Adjust to Ground check the datasheet page 7 first

    http://www.ti.com/lit/ds/symlink/lm137.pdf

    Also your transformer secondary is wrong!
     
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  3. ClimateController

    Thread Starter New Member

    Dec 23, 2012
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    Thanks for the reply, Dodgydave. Could you please be more specific about the transformer issue?
     
  4. absf

    Senior Member

    Dec 29, 2010
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  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    put the ground to the Centre tap, and not to the end terminal.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    LM317 and LM337 are voltage regulators. You don't need the two resistors and the zener that you have added to each output. You will only be able to get a few milliamps out of each supply, the way you have it drawn.
     
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  7. ClimateController

    Thread Starter New Member

    Dec 23, 2012
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    Thanks, Dodgydave, that did the trick! Ron H, I am using the zeners to limit the output voltage to positive and negative 12 V and positive and negative 5V. I do not know any other way. I removed one of the resistors and 65 mA is the best the power supply can do. Could you please tell me how I can increase the current? You guys have been immensely helpful so far. Thanks!
     
    Last edited: Dec 23, 2012
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    How much current do you want to each output to be able to deliver?
     
  9. bertus

    Administrator

    Apr 5, 2008
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  10. ClimateController

    Thread Starter New Member

    Dec 23, 2012
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    Thanks for the link, Bertus.

    @Ron H
    5 A. Enough to turn on a lamp.
     
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