Why use full wave rectifier with DC?

Discussion in 'The Projects Forum' started by Sigh, Mar 4, 2009.

  1. Sigh

    Thread Starter New Member

    Mar 4, 2009
    3
    0
    Hi,

    I was thinking of making this breadboard power supply I found on instructables.com but I have a question about the design.

    Schematic:
    http://www.instructables.com/id/SH4XFE9F3ETRWKZ/

    Why does it use a full wave rectifier when the input is using a DC power jack (DCJ0202)? Is it because then you can use an AC-AC adapter?
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Sometimes new students inadvertently hook the power up backward when experimenting.
     
  3. TWRackers

    Active Member

    Dec 29, 2008
    41
    2
    It's also a handy technique if, for example, you have a signal that's going to drive an LED (or in my project, the input side of an optoisolator), and you don't know with certainty the polarity of the signal.
     
  4. Sigh

    Thread Starter New Member

    Mar 4, 2009
    3
    0
    Would I be able to use an AC-AC adapter?
     
  5. packrat

    Member

    Feb 25, 2009
    12
    0
    Most likely(if you follow all the directions to the letter, specifically regarding the V rating on the input cap), though you wouldn't want the adapter to exceed 40V as thats the limit of the LM317.
     
  6. Sigh

    Thread Starter New Member

    Mar 4, 2009
    3
    0
    awesome. thanks
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    I would also use a bigger capacitor. A heat-sink on the regulator would be a good idea when working with the lower voltages, especially if the AC input is much more than 9Vrms.
     
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