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Thread: Clean 12V Supply

  1. #1
    Variable Bitrate
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    Question Clean 12V Supply

    Is there a convenient way to get a clean supply out of the regular battery line when powering an LCD other than using the computer supply? Magic voltage reg. perhaps?

  2. #2
    Maximum Bitrate albysure's Avatar
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    I would probably use the computer power supply to keep it simple. that way, everything would have the same power supply possibly avoiding ground loops and interference.

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    Maximum Bitrate gizmomkr's Avatar
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    Radioshack sells a 12v voltage regulator.

    I would say, 2 of these in parallel, with a capacitor, small 5K resistor, a diode or 2.
    You could even throw in an rf choke for good measure.

    You could use the voltage reg by its self, the other stuff is just to clean it up a bit. You need at least 2 voltage regs, cuz the ones at the shack are rated around 1 amp I think. you want to make sure you cover the power requirements for the lcd.
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  4. #4
    Retired Admin Aaron Cake's Avatar
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    Cool

    Paralleling voltage regulators is very tricky, as one will always sink more current then the other. In that situation, one will heat up faster and go into thermal cutout. The other will then do the same, at which point they will both cool down and the cycle will repeat. If you are going to use regulators, get the TO-3 equivelant of the 7812, or just use the PC power supply. You will also need filter capacitors no matter what approach you take.

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  5. #5
    Maximum Bitrate gizmomkr's Avatar
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    Never knew that about regulators, thanks aaron.

    I would of course advocate the use of the pc supply, but Im guessing 2 reasons why not :

    1. its on an inverter, and has lot of noise.
    2. you have a small DC-DC , and if you hook up the LCD it will overload the DC supply.
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  6. #6
    Newbie
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    Gudday,
    Would you have this trouble running the max series of voltage regulators? Am planning on building a Dc-Dc PSU similar to the sproggy design, but I want to doubble up on the current...was considering just doubbling up on the circuits (ie. 2 * 5v etc)Hmmm
    Cheers,
    Fab

  7. #7
    Variable Bitrate
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    any schematics out there for these circuits you guys are talking about?

  8. #8
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    Lightbulb

    Check my website, it has schematics and PCB layout for a simple DC-DC converter.
    http://mp3.kempen.org/
    I build it myself, it supplies 5V@10A (two MAX787 in parallel) and 12V@3A (with the MC34167T). The regulators and coils can be ordered FOC as samples (check the links in the menu).

    Erik Kempen
    The Netherlands

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