Power supply output Current?

Discussion in 'The Projects Forum' started by Bigbizkit, Dec 20, 2015.

  1. Bigbizkit

    Thread Starter Member

    Oct 29, 2015
    44
    1
    Hi guys... Im just confuse here.. I have a 3A 24V power transformer.
    I used it in my diy pedals as a bridge type power supply.
    Just wondering what output current will i get if i use a 78XX series voltage regulator since this regulators has an output current of like 1-1.5A.
    2. Does anyone has a dual voltage regulated power supply schematic? Hmmm.. A 3A/15V power supply perhaps?
    Would you be so kind to share it?
    Thank you very much!
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,884
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    The 78XX will at least try to supply the current required. After that it will overheat as it exceeds it's rating and then eventually fail. The capabilities of the transformer really have nothing to do with it.

    Please be aware that if you are considering powering something like a 7805 then you will need to dissipate the excess voltage through heat. You would be better to find a transformer that more closely matches your required output or
     
  3. Bigbizkit

    Thread Starter Member

    Oct 29, 2015
    44
    1
    Thank you very much spinnaker.
    Another question, i use lm317 adjustable voltage regulator, when i turn my 2 pedals on it cuses hum especially on high volume... What do u think is the prob?
     
  4. hp1729

    Well-Known Member

    Nov 23, 2015
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    Get a data sheet for a 78xx voltage regulator of your choice. They usually have suggestions for higher currents and other options. http://www.alldatasheet.com is a personal favorite place to get data sheets. The best data sheets are too big to post here. Or just google for it.
     
  5. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Probably filtering. Post your schematic. Others here with far more experience than me might be able to help.
     
  6. Bigbizkit

    Thread Starter Member

    Oct 29, 2015
    44
    1
    The schematic below is a dual voltage by elliot sounds,
    I just use the positive output of the schematic using 1A power transformer.
    I thought it would work...
     
  7. hp1729

    Well-Known Member

    Nov 23, 2015
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    Some options using fixed voltage regulators
     
  8. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,234
    Note that a transformer should be derated to no more than about 60% of it's RMS rating when used to generate DC using a bridge rectifier and capacitor filter.
    Thus your 3A transformer is good for about 1.8A DC max. from the rectifier-filter output.
     
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