Non-polar dc power supply

Discussion in 'General Electronics Chat' started by icyhot01, Jun 25, 2011.

  1. icyhot01

    Thread Starter New Member

    Jun 25, 2011
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    Hello guys. I'm basically new to electronics and our classes has just began. Our prof is asking us to create a reversible(no polarity) dc power supply. eg. if i put +12v or -12v the output will be +5v. Can anyone help me on where or how to start with this. thanks in advance.
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    One possible (partial) solution might include the use of a bridge rectifier.
     
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Bridge rectifier feeding DC-DC converter (any surplus car USB power supply or phone charger).
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    There is an introduction to how a bridge rectifier works on this page:
    http://www.allaboutcircuits.com/vol_3/chpt_3/4.html
    I suggest stopping when you get to the 3-phase rectifier, or you may become confused; it's a bit much to absorb in the beginning.

    You can go to the various chapter headings if you wish to learn more about diodes and rectifiers.

    For regulation of the output at 5v, you might consider using an LM7805 regulator, or an LM317 adjustable regulator. Both of those will require capacitors on the inputs and outputs. The LM317 will additionally require two resistors to set the output voltage. Find the datasheets for these regulators and study them.

    For the LM317, I'll suggest using 120 Ohms for R1 and 360 Ohms for R2. The basic schematics are in the datasheets under Typical Applications.
     
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