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Yet Another Voltage Regulator Thread

Discussion in 'General Electronics Discussion' started by ChrisQ, Apr 1, 2011.

  1. ChrisQ

    ChrisQ

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    Mar 10, 2011
    I searched and read through several threads on the subject, but I will need more basic help than has previously been sought.

    I have my LM317. Now I need to acquire the rest of the parts for my circuit. I read and understand the schematic and the parts list. I do NOT understand the computations yet.

    Input will be 12v from an ATX power supply.
    Output will be no more than 9v and as close to 6v as I can get it without overheating. This output will not be adjusted.

    Looking at the pic below, I am thinking of moving the fan to the outside of the power supply, and then mounting the VR board in it's place but off to the side as to allow some flow to the rest of the unit. This should allow the LM317 to stay plenty cool.

    [​IMG]

    I found this guide: http://www.rigacci.org/docs/biblio/online/voltreg/fan-regulator/tutorial-full.html and since this guy is also starting with 12v input, I am hoping I can use his calculations and build it exactly like he did (except for the molex connectors).

    Will this work for me?
     
  2. davenn

    davenn Moderator

    13,168
    1,714
    Sep 5, 2009
    a consideration you have not commented about is what current drain is the load you are putting on the output of the LM317 ?

    Dave
     
  3. MattyMatt

    MattyMatt

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    Mar 24, 2011
    My one question to you, is if the load on the power supply will be low, you can see how high the +5v rails are... sometimes they get as high as 5.75v.... just a thought.
     
  4. ChrisQ

    ChrisQ

    32
    0
    Mar 10, 2011
    At davenn - I will be building 2 of these VR's to step down 2 different ATX power supplies.

    My project thread spells it out more.

    The first I am building is the test box on my bench and that box will just be one lighting kit at a time. The load will be negligible, but will be different with each ship I build. Most of them will just be 5 or 6 LEDs and the occasional blinker board.

    The second will go in the display room and power all the ships. Since I will be gradually adding more ships to the circuit as they are built, the load will gradually increase over time.

    As you see in the other thread, it is not expected to exceed 1A when all is done.

    For MattyMatt: I had not thought about that. The power supply is rated for 25A on the +5v rail. If my current never exceeds 1A, that would likely be low enough. However I'd hate to start building models and realizing that my LED's aren't bright enough or my boards are blinking too slowly or something.

    If you could explain the perils of undervolting these lighting kits I would be appreciative.
     
    Last edited: Apr 1, 2011
  5. ChrisQ

    ChrisQ

    32
    0
    Mar 10, 2011
    I did it! And by that I mean it actually works. My first circuit ever. I thought I was going to fry it for sure with my mountains of solder. I need to get a pointy tip for that thing.

    [​IMG]
     
  6. MattyMatt

    MattyMatt

    154
    0
    Mar 24, 2011
    Under powering varies a bit, I've had an LED that was just kinda dim, where as others, it just simply didn't work.... I have heard of people prematurely frying them... but I don't know if its true (I would expect that it could be...).

    Globs of solder will always still work! it may just look a little sloppy or interfere with something else :p

    MattyMatt-
     
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