Power supply different volts and maps

Discussion in 'The Projects Forum' started by paddyhughes086, Sep 9, 2011.

  1. paddyhughes086

    Thread Starter Active Member

    Jan 30, 2011
    48
    0
    I was working on a project a while ago. It’s a mixture of a few circuits. It involves an iPod docking station, set of speakers and led vu meter.
    The iPod doc runs on 5v at 1A…..all do I did find a way on the internet to change it to run on 500ma
    SPEAKERS run on 15v at 500ma
    And the vu meter runs on 12v at just shy of a 1A
    My issue is I’m using 3 power supplies that are all on the outside of the unit so it doesn’t look neat I would like to use one power supply that could deliver all these volts and amps does anyone know or could suggest to me a way to sort this out.

    Thanks for any help given
     
  2. JingleJoe

    Member

    Jul 23, 2011
    185
    10
    A computer ATX power supply would be able to do that, there's alot of stuff around the internet about it's pinouts and how to make it run without the computer attached :)
    Now it can only provide 3, 5, and 12 volts so you may need to find speakers with lower voltage requirements, but they may run fine from 12 V, as for current requirements it should handle your things fine.

    However before you do that I have some mroe questions, are those current readings taken from an ammeter or from the power supply?
    Because the rating on the psu is just the maximum it can provide, those currents are often not drawn by whatever is connected to them.

    Additionally one could make one's own power supply box with voltage regulators and a single big transformer/rectifier/filter stage, then you can tailor it to your own voltage and current requirements. I recommend the L78xx or LM78xx voltage regulator IC's (the xx indicates voltage output, e.g. L7805 or LM7812)
     
  3. paddyhughes086

    Thread Starter Active Member

    Jan 30, 2011
    48
    0
    sound good the meserments were taking form the power supplys. i would be intrested in making my own power supply. thanks for your help
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    Then first find 15VAC, secondary rated transformer . Primary should be rated for ur mains Voltage. Power can be around 50VA
     
  5. paddyhughes086

    Thread Starter Active Member

    Jan 30, 2011
    48
    0
    have a quick qestion if i get PCB Open Mains Transformer so 240ac to 12dc at say 6 amps.

    but my device only needs 12v and one amp dose it matter that the transformer puts out more amps than the device needs.
     
  6. paddyhughes086

    Thread Starter Active Member

    Jan 30, 2011
    48
    0
    dose that not neet to be 15VDC, secondary rated transformer
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    The Load only draws it's required current even though the supply is rated higher. The Voltage is the main concern here.
    And a transformer output is always VAC.

    I asked for a 15VAC so that the it would have enough headroom for the standard regulator drop out.
    A 12VAC will give an DCV of 12 X 1.414 = 16.9VDC at no load. So the regulator dropout will be at no more than 12VDC - 16.9VDC = 4.9V. Which is OK under light load conditions. But at ur rated load of 1Amp I think this is a little low.

    At 15VAC the regulator will have good line regulation.
    U can test this if you have a 12VAC output tx as said above.
    It will work with what you have.
     
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