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Electronics Simple voltage converter, how?

Discussion in 'Modding' started by Twellmann, 8 May 2006.

  1. Twellmann

    Twellmann Carnivorous Homunculus

    5 Jan 2004
    Likes Received:
    I need a simple voltage converter circuit :D

    I need 1,2V out and I wan't to be able to hook it up to various batteries, 7,2 9 or 12 volts or the likes

    I'm not quite sure as to how much current I need out of this thing, but no more then 1 amp

    It will drive the glow plug on a Nitro RC car

    In short:

    2-20 Volts in

    1,2-1,3 volt out max 1000mA


    I guess this could be used at Farnell #9493301
    Last edited: 8 May 2006
  2. Confused Fishcake

    Confused Fishcake New Member

    25 Sep 2005
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    Just get any fixed 1.2V voltage regulator, or use one like the one at farnell. Basically, any electronic company will sell something suitable, best if you can get a fixed 1.2V one. (Less parts)
  3. Starman97

    Starman97 New Member

    17 Sep 2003
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    You can use a linear regulator like the LM317T (see digikey)
    The only trick is that if you pull 1 Amp from the output,
    that means 1 Amp is pulled from the input power source.
    That's all fine, but 1 Amp at 1.2V is only 1.2 Watts,
    what happens to the (20v - 1.2V) * 1Amp = 18.8W ?
    It gets turned into heat in the regulator. So you're going to need a
    BIG heatsink if you run this for more than a minute or two.
    Even if you only run it for a few seconds, you still need a heatsink,
    that TO-220 package will burn out with 18W.

    Your other option is a switching power supply. These are more expensive,
    but far more efficient. The problem is, finding one that fits your
    requirements of 3-20V in and 1.2V @1A out. Not a big problem if
    you can design your own. Look up National Semiconductor's Simple Switch
    line, they have a web-based circuit designer. They also sell SimpleSwitch
    kits, not cheap, but they do what you want.
  4. Wolfe

    Wolfe New Member

    7 Sep 2003
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    The lm317 only goes down to 1.5 v
  5. cpemma

    cpemma Ecky thump

    27 Nov 2001
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    Nominally 1.25V (+/-0.05V) which shouldn't hurt, and you could treat it as a fixed voltage regulator, no need for any resistors. Just connect the adjust pin straight to negative. Presumably this is only on for a short time, so whilst you need a decent heatsink it doesn't need to be enormous.

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