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Thread: All in one power supply...HOWZZAT???

  1. #1
    Junior Member User
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    Default All in one power supply...HOWZZAT???

    guys i was abit worried about what power supply to use for my hexapod which uses 12 servos ......... i was looking for a 6 volt regulator that could provide about 10 amps.... i couldnt find any such ic but you know what??
    i googled the topic and accidentally there were a few links on pc power supplies.....i went thru them out of sheer boredom and i think i might have hit paydirt.

    i found that standard ATX power supplies have power o/p s of 12 volts, 5 volts, 3.3 volts and sometimes -5 volts and -12 volts and are capable of providing about 15 amps in the 12 volt rail and 10amps easily in the 5 volt rail. amps in the other rails were just as impressive. the best part ??
    it connects to plain old 230 v ac line.
    i think it will serve well on the robots which are large in size and even in the testing stages where one doesnt want to go in fo a battery just yet.

    these things have pwm voltage regulation and are very very accurately controlled internally so u dont have to worry about voltage surges damaging ur precious servos.

    i wanted to put this before the more experienced guys out here... who may have thought along the same lines sometime. is this ok??? AM I MISSING OUT ON A CATCH SOMEWHERE? i would like to hear your opinions people!

  2. #2

    Default

    3d,

    That was some nice piece of information, thanks. Did u confirm that the 5v rail provides 10A?

    regds

    happy_99

  3. #3

    Default

    the only possible option is to use an SMPS

    That can provide upto 40A(of a 486 pc)

    +-5 and +-12v available


    Bibin John
    www.bibinjohn.tk

  4. #4
    Junior Member User
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    Default somehow it didnt work.

    .well guys guess what the thing didnt work as i expected it to work. we screwed off a smps from a comp... and through a multimeter checked which pins provided 12 v and which ones provided 5v ..... we found the 5v rail but we didnt find the 12v rail.....????????????? how is that possible and the most depressing part was that the 5v supply dropped to 1.5 volts as soon as we loaded it with the servos.

    can anyone ... specially the comp engg. guys suggest any reason as why this happened? as i see this occured because you cant use a smps in the stand alone mode ie disconnected from the computers motherboard.... nowadays these supplies are not mere power providers but are electronically controlled from the motherboard and i guess a feedback path was not activated due to which the supply did not turn on the 12 v rail and went into standby in the 5v rail whose max current in the standby mode is generally in milliamps......is my conjecture correct? i woul like to hear some ideas and any method to surpass this.

  5. #5
    Guest

    Default

    If it is a ATX supply, you have to ground PS_ON wire to turn on the supply. Usually the green wire on the big connector. Short this to a black wire.

    To get 5V and 12V, use the 4 pin connectors, red is 5V and yellow is 12V. The two black wires are gnd.

  6. #6

    Default

    Here's a circuit for increasing the output current for LM78xx voltage regulators

    http://www.mitedu.freeserve.co.uk/Ci...wer/boosti.htm

    Check this too

    LM138 - 5A Adjustable regulator

    http://www.national.com/pf/LM/LM138.html

    Regds

    happy_99

  7. #7
    Junior Member User
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    Default hey thanks guys........

    thanks for the cool links happy_99 . and i will surely try out our guest's solution and let you people know . join us here at roboticsindia by becoming a member. we look forward to your participation on our pages.

  8. #8

    Default

    Check out the datasheet of LM138 too !! There are application circuits for 15A/10A regulated supplies using 2-3 LM138's together.

    http://www.national.com/ds.cgi/LM/LM138.pdf

    Regds

    happy_99

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