Power Supply Help Please ?

Discussion in 'General Electronics Chat' started by HaseebEngineer, Aug 12, 2013.

  1. HaseebEngineer

    Thread Starter New Member

    Aug 8, 2013
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    I have made this power supply to have an output of 30v , 4ampere .. I have also implemented this on a breadboard...my Digital Multimeter is giving an output from 3v to 30v with this regulated power supply ... But the current is not 4ampere ... its about in miliamps ... WHY ????? Why ???

    My transformer output is 24v RMS and 8Ampere ... The rectifier i used are 4x1N4007 ...
     
  2. #12

    Expert

    Nov 30, 2010
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    Because there is nothing attached that can use up 4 amps. What do you want it to do? Shove 4 amps through the meter?
     
  3. wayneh

    Expert

    Sep 9, 2010
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    Maybe because there is no load except air? How much current were you expecting to drive through the air?

    Dang, #12 beat me again.
     
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  4. tubeguy

    Well-Known Member

    Nov 3, 2012
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    1n4007 diodes are rated at only 1 amp. You need proper diodes. Best to use a ready-made bridge rectifier at least 8 amps.
    It's not safe to hook a 30 volt zener directly across a 30 volt max supply. (everything has tolerances)
     
    Last edited: Aug 12, 2013
  5. PackratKing

    Well-Known Member

    Jul 13, 2008
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    Levity aside, tubeguy is right about the inadequate diodes.

    Shouldn't OP have a load resistor immediately downstream from the filter cap @ C1 after the rectifier ? Re: the thumbnail... or does the load res. belong at the output end...

    Also Tantalum caps on the input / adjust for the U1, and a cap on the output ??

    There are so dang many ways to skin this cat, is why I ask...:rolleyes:
     
    Last edited: Aug 12, 2013
  6. #12

    Expert

    Nov 30, 2010
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    He should also have C2 on the other side of the 500 ohm resistor, but it seems futile to clean up the details when the OP doesn't even know what current is.
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,647
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    Hello,

    What is R3 ( 500 Ohms ) doing at the input of the regulator?
    This will limit your output current dramaticaly.

    Bertus
     
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  8. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
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    I smell magic smoke... :D
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Even with R3 removed, which is critical, the current at 30V will be limited since this is well above the 24V rms rating of the transformer, for which we don't know the current rating.
     
  10. wayneh

    Expert

    Sep 9, 2010
    12,101
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    There's not even enough current to release the smoke monster!
     
  11. LDC3

    Active Member

    Apr 27, 2013
    920
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    I believe it's called 'phlogiston'.
     
  12. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
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    Read about that theory once...:D Aw what the hey... They didn't know any better at the time
     
  13. LDC3

    Active Member

    Apr 27, 2013
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    I'm saying that the magic smoke is called phlogiston. ;)
     
  14. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
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    Its better to use single rectifiers rated for the job, than putting 4 in parallel to make up the rating - manufacturing tolerance means one diode will conduct more than the others and fail S/C! You also need a safety margin - a bridge rectifier rated at least 6A.

    If you mean the 4x 1N4007 are the bridge rectifier - you'll be letting the magic smoke out pretty soon.

    I do hope there's a fuse protecting the secondary of the transformer!!!
     
  15. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    Take R3 away and shorted two pins.
    Take D3 away.
    Bridge rectifier - 100V/6A(>=60V) or rectifier diode - 100V/6A. (>=60V)
    D1,D2 → 100V/4A (>=60V)
    C1 → 2200uf/50V
    C2 → 470uf/50V or 220uf/50V
    Vout in parallel with a 0.1uf/50V (Multilayer Ceramic Capacitors)
    AC220V in series with a fuse. (0.87A fuse for 24V/8A output, could using an 1A fuse)
     
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