Reversing the polarity of a power supply

Discussion in 'The Projects Forum' started by true bypass, May 28, 2008.

  1. true bypass

    Thread Starter New Member

    May 17, 2008
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    I'm trying to reverse the polarity of a circuit which normally is positive grounded. I want it to be negative grounded.
    [​IMG]
    I think this should do it, but am unsure, can someone please tell me if this will work or not? Am I missing something?
    [​IMG]
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You might want to use NPN transistors and just reverse the battery and the capacitors. 2N2222's should work just fine.
     
  3. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
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    Besides using NPNs insead of the PNPs, like beenthere said, you should invert the electrolytic capacitors (10uF and 25uF) as well. That way, they will not explode when you turn your circuit on.
     
    Last edited: May 29, 2008
  4. true bypass

    Thread Starter New Member

    May 17, 2008
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    0
    but, if i for some reason wanted to use PNP's, is this circuit right?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    1,728
    It won't work with PNPs.
     
  6. true bypass

    Thread Starter New Member

    May 17, 2008
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    0
  7. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
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    You have to use the transistors in common emitter configuration, like proposed in the circuit. That is why PNPs won't work.

    In the article you've shown, he is using the battery in a manner that the current biasing the transistor will flow in the same way. He is using a negative ground now but the ground is connected to the collectors of the transistors, making the circuit essentially the same. Of course it is bad construction practice having a ground plane connected to the collectors of the transistors, since a ground plane is a large conductor and will bring some oscillation. He even mentions that, but a good construction practice is not what he mentions.
     
    Last edited: May 29, 2008
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