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Power Supply pcb

Discussion in 'Circuit Simulation & PCB Design' started by emb, Aug 18, 2017.

  1. emb

    emb Member

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    hi all.

    i'm new in pcb design ..i'm trying to design pcb for power supply..

    schematic

    ps.jpg

    layout
    psl.jpg
    is my design correct ?
    or,
    are there any considerations should i take in my account ?

    regards
     
  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi emb,
    I would increase the width of the -V track from rectifier to the common 0V.
    Also I would not use the GND annotation on the silk screen, call it 0V.
    Flip the H/S so that it does not over hang the edge of the PCB,
    The +5V/0V TB corner should be supported with a mounting hole.

    What is the spec on the supply transformer secondary.?
    E
     
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  3. emb

    emb Member

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    thank you :)

    i used 70th trace width
    and for 5V 60th trace width
    power plane clearance 20th
    pad-pad clearance 12th
    pad-trace clearance 12th
    trace-trace clearance 12th

    :)
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    I guess you know that for an output current of 1 amp you will drop at least 7v across the 7805, that is 7 Watts.
    On lesser load currents the smoothing cap could charge to [12 * 1.4] - 2 Diode voltage drops, that is approx 15V.

    E
     
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  6. emb

    emb Member

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    i dont know that :(

    what are the effects of these values o_O ?!
     
  7. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Just a comment about the schematic, It's normal to have the power rails at the top and bottom and have components vertical between them where possible.
    Here is your schematic drawn in this fashion,
    Power Supply.png
    I hope you will agree that it is much easier to follow. When laying out schematics and designing components try and keep the same grid size and alignment will be much easier.

    Mike.
     
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  8. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    Make sure your H/S can keep your 7805 within its temperature specification, if it over heats choose a larger version.
    This is assuming that you will be running at a continuous 1Amp load, which would be unusual for a 1 Amp power supply.
    Rate your smoothing cap for say 25V wkg voltage.

    Have you built a prototype of the power supply and had it on test.? it would be advisable to do so before committing to a PCB artwork
     
  9. emb

    emb Member

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    thank you guys :)

    the load up to 500mA :)

    no,I haven't :/
    i will test it before printing the PCB ^^
     
  10. Pommie

    Pommie Well-Known Member Most Helpful Member

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    If you drop the transformer to 9V your regulator won't get as hot. However, the 1,000uF capacitor on the input may be too small - it you can fit a larger capacitance it would be better - maybe 2,000uF 25V - may be 16V.

    Mike.
     
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  11. emb

    emb Member

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    if i do all the advises mentioned here ,is there any thing should be modified ?

    should i use fuse on primary side ?

    emb
     
  12. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Using a 2A in place of a 1A regulator will not reduce the heating effect.
    If the primary mains side of the transformer is is fused at a rated 3Amp, I would not fit an additional fuse.

    Is this PSU for your bench projects.?
    E
     
  13. emb

    emb Member

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    I built a circuit using MCU to control the motor (on|off/timer) so i need to supply this circuit with that PSU :)

    Fuse of 1A rated enough ?

    regards :)
     
  14. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    This is "picky". I would make the grounds stronger.
    Example move R1 to get ground across the top.
    Try to get the right side ground to reach U3-2 more direct.
    Try to get C1,2,3,5 to connect to J2 better.
    upload_2017-8-19_14-13-17.png
     
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  15. emb

    emb Member

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    thank you :)

    layout after modification
    ppp.jpg

    o_O
     
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  16. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I like your new ground!

    I see these red circles. Why? Did you move the holes? I think something is not right.
    upload_2017-8-19_16-45-12.png
     
  17. emb

    emb Member

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    popo.jpg

    traces width suitable ?
    70th and for 5v 50th ^^
     
  18. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi emb,
    If the PSU was for a bench testing supply, I was going to suggest adding a 7809 [9v reg] ahead of the 7805.
    This would mean you could use the existing 12V transformer, reduce the heating in the 7805 and giving a +9v and +5v supply for your projects.
    E
     
  19. emb

    emb Member

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    Thanks Eric
    I have PUS for my work bench with 5v 9v 12v 28v ^^

    Bt I want the power supply mentioned here to supply a circuit used to control motor using pic microcontroller ^^

    EMB
     
  20. Chris Edwards

    Chris Edwards New Member

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    power supply pcb.jpg
     
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  21. JonSea

    JonSea Well-Known Member

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    Not to discourage you, but for my micro projects, I use a USB power supply like tbis or an old cell phone charger from the thrift store or pc-recycler. Power plugs like the one shown are available for $5 or less.

    SmartSelectImage_2017-08-28-07-26-19.png
     
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