First designed schematic, please check

Discussion in 'The Projects Forum' started by Adamf001, Aug 6, 2012.

  1. Adamf001

    Thread Starter Member

    Sep 5, 2011
    67
    2
    Hello again AAC,
    taking some of your guys advice I have finally designed a power supply for a few projects etc...
    The circuit involves using the voltage adjuster LM317 and LM337

    could some of the experienced designers just give my schematic a once over, make sure there is no obvious faults. and as another question, do I need that Capacitor that I have circled? if so why?
    (Sorry for the poor scanning quality)(both attachments are the same)

    I designed the circuit by combining the best bits of a couple of a designs
     
    Last edited: Aug 6, 2012
  2. #12

    Expert

    Nov 30, 2010
    16,343
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    Your chip usage is good but your transformer connections have a fault.
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,394
    1,607
    Your trying to split a single transformer to get both positive and negative outputs. You can't do that (with or without C1). You need a center taped transformer to get both plus and minus outputs. Or a second transformer.

    The 10 uF on the ADJ terminals may slow the response when you adjust the pots. I would leave them out.

    Those pots will be drawing up to 10 mA when nearing zero volts, so make sure they can handle that.
     
  4. #12

    Expert

    Nov 30, 2010
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    You can't get there with that transformer. Try this.
     
  5. Adamf001

    Thread Starter Member

    Sep 5, 2011
    67
    2
    ok, I understand that so would I be able to place a secondary transformer in place of C1?

    and how would I get a negative supply from the secondary transformer, because I think I need a negative supply being suplied to the LM337? or not?
     
  6. Adamf001

    Thread Starter Member

    Sep 5, 2011
    67
    2
    I think your Idea would be better than using two transformers, and I see how you can get a negative supply, thanks 12...

    but just for arguments sake I'd like to know how I'd do this with two transformers??
     
  7. #12

    Expert

    Nov 30, 2010
    16,343
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    Just use the secondary winding of the second transformer as a continuation of the secondary on the first transformer. The point where you attach them together becomes the "center tap".
     
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