Power Supplies

Discussion in 'General Electronics Chat' started by Johndon2000, Jun 12, 2013.

  1. Johndon2000

    Thread Starter New Member

    Jun 12, 2013
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    Hi,

    I have 2 power supplies but I need to obtain 3 voltage levels (+5V, +12V, -12V) to bench test a circuit board… is there a simple solution or do I have to use 3 power supplies?!

    Many thanks,

    John.
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    ideally you would need a -12V 0V +12 Volt psu, so you could the drop the +12 to +5 with a 7805 regulator.

    What psu voltages do you have?
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    Here is how to connect to batteries to get +/- 9 volt. Just connect your power supplies the same way. To get the +5 volt. Use some voltage regulator like the LM7805 or LM317
     
  4. Shagas

    Active Member

    May 13, 2013
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    Some computer power supplies provide +12v at high amperage , -12volts at low amperage and 5 volts at high amperage so If you got one of those that does it and if your circuit board doesn't need to much amperage at the -12v then you can u se it straight up I think
     
  5. Johndon2000

    Thread Starter New Member

    Jun 12, 2013
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    Hi guys, thanks for that!

    The Power supplies are 3A/60V and 10A/30V.

    Looks like a voltage reg is the way forward, so I just need to +12V and -12V from the 2 PSU's... thanks.

    Think the power rails will need about 3A each, so I'll check out the 7805 and LM317 specs.

    Thanks again guys :)
     
  6. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    So if theses are ground isolated types, you could join them together + to - and make a centre zero psu , then you just need an LM337(neg) and and two LM317(pos) to give you the voltages you need , just omit the bridge rectifier.

    PSU
     
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  7. Johndon2000

    Thread Starter New Member

    Jun 12, 2013
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    Thanks Dave, I'll try that :)
     
  8. t06afre

    AAC Fanatic!

    May 11, 2009
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    Unless you can adjust the output voltage from your current power supplies, you will not be able to do as suggested. First the LM317 will fry at 60 volt. And then you will also have huge problem with power dissipation. That will also kill the voltage regulators. I suggest you go for using a old PC power supply instead.
     
  9. Shagas

    Active Member

    May 13, 2013
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    The LM regulators give up to 1-1,5 amps max I think . If you are going to want more current then you will need to use a shunt power transistor with the Lm regulators.
    I can provide a link to schematic if interested

    Also , as mentioned above , 60 volts will fry the regulators . They are rated for 32 volts max I think
     
  10. Shagas

    Active Member

    May 13, 2013
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    74
    Are you sure you need 3A to test a circuit board??
     
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