Help with change in schematic

Discussion in 'General Electronics Chat' started by medmike, Oct 16, 2014.

  1. medmike

    Thread Starter New Member

    Sep 28, 2014
    4
    0
    The schematic top left shows transformer from mains to 24 v (looks like ac) with bridge rectifier converting to dc. I have an old Acme Transformer that is 120 ac to 24 dc. So I would need to just eliminate rectifier correct since my transformer (here is link same transformer http://www.voytenelectric.com/us/ta-1-81141-transformer-by-acme-industrial-p109252.html) goes to dc? (Keep 63 v cap for smoothing? )

    Here is project info link for flyback high voltage power supply = http://jnaudin.free.fr/lifters/labhvps/

    Thanks in advance!
    Mike
    [​IMG]
     
  2. Brevor

    Active Member

    Apr 9, 2011
    279
    54
    No, the transformer you linked to has a AC output, you need to keep the bridge rectifier.
     
  3. medmike

    Thread Starter New Member

    Sep 28, 2014
    4
    0
    Thanks Brevor...I will confirm with my DMM (I should have done that anyway!) .
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,360
    AC or DC, you can leave the bridge rectifier in the circuit.
    1) It would not make a noticeable difference.
    2) It gives you protection from reverse polarity, i.e. you can connect the output of the DC adapter either way with no harm.
     
  5. medmike

    Thread Starter New Member

    Sep 28, 2014
    4
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    Quick ground question, does mains ground connect to transformer T1 and do the dc side grounds connect to chassis?
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,360
    You have a choice to do it either way.

    It is common for commercial bench power supplies to be "floating", i.e. that there be no connection to AC mains ground.

    Mains ground must be connected to any metal frame or chassis of your project for electrical safety.

    If you are building a general use bench power supply then presumably you will use two banana jacks connected to the +VE and -VE sources of the DC output. Then you will provide a third banana jack connected to chassis GND.

    This gives you the option of having a power supply that can be configured as +VE or -VE with respect to GND depending on which jack is connected to GND.

    Notice the external strap between the -VE terminal and GND as seen in the photo below:

    [​IMG]
     
    Last edited: Oct 17, 2014
  7. medmike

    Thread Starter New Member

    Sep 28, 2014
    4
    0
    Thanks MrChips!! Will get chassis (and transformer, since will be chassis connected anyway) to mains ground and will have dc out with chassis ground out
     
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