voltage regulator circuit

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onekill
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voltage regulator circuit

Post by onekill » Wed May 25, 2005 8:41 pm

I am looking to build a power supply for a project. It will be running a computer and some other devices connected to it.<p>so I am thinking a +-5v, +-12 volt will do everything I need. I would like to build it between 3 to 6 amps. <p>is this feasible to do with a pack of lithium poly's stacked to create a 14.4 battery?<p>I know there is issues with lithium poly's(fire and charging), but weight is an issue. <p>also how clean do I need to make the DC, since it is running micro devices?<p>I have looked at using lm317's, but I am also interested in switching power supplies.(due to heat and a cleaner signal)<p>I would like to here pro's and con's about the two types above. <p>any ideas and pointers are greatly appreciated...<p>
TIA
James

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Re: voltage regulator circuit

Post by ezpcb » Wed May 25, 2005 9:34 pm

317 will bring you night mare at this application. You must install a large heat sink to aviod it from burning at 3-5A current.<p>I strongly suggest you using DC-DC modules with built-in stablized circuit. linear regulator is cheaper, and less EMI. but it generate terrible heat in high current applications. DC-DC is expensive, but has higher effeciency and generate less heat. <p>'clean' doesn't affect the motherboard greatly, there're many filter circuits on the board.
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Michael J
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Re: voltage regulator circuit

Post by Michael J » Thu May 26, 2005 5:14 am

What's wrong with using an old PC power supply.<p>
~ ;o)

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philba
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Re: voltage regulator circuit

Post by philba » Thu May 26, 2005 6:47 am

The 317 (from national, anyway) has an absolute max current rating 3.4 A but, as pointed out, that is with a huge heat sink. I wouldn't design a circuit that runs up anywhere close to the spec'd limits. The 317 spec's go to h*ll when the temperature gets pretty high. You can do a number of things to get higher current but it gets more complex. See the national datasheet.<p>If your goal is to learn by building a power supply, then go for it but if your goal is to power some circuits, I'd suggest an off the shelf power supply. The computer power supply suggestion is a good one.

onekill
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Re: voltage regulator circuit

Post by onekill » Thu May 26, 2005 7:51 am

using a pc power supply is a great idea. But weight is an issue. This stuff is going in a R/C airplane. So, weight and heat is an issue.<p>Thanks for the ideas so far...<p>Keep em comming please<p>TIA
James

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Re: voltage regulator circuit

Post by dyarker » Thu May 26, 2005 8:25 am

A computer that needs 3 to 5 Amps is a big computer to put in an R/C plane, must be a BIG R/C plane. And batteries too! Even with lithium, a 5 to 10 AmpHour stack for primary power is going to be heavy.<p>IMO you need a DC to DC module. 12V (nominal) in, +-5 +12 out. It would be hard to build one lighter and smaller.<p>Just an idea - with microcontroller (PIC, Stamp, Zilog, etc) and RF MODEM on board, you can just use +5 at under an Amp. Weight goes WAY DOWN. Do the number crunching in the ground.<p>Cheers,<p>[ May 26, 2005: Message edited by: Dale Y ]</p>
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Engineer1138
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Re: voltage regulator circuit

Post by Engineer1138 » Thu May 26, 2005 10:33 am

That brings up an interesting question: has anyone ever connected a generator/alternator to a small R/C gas engine? Think of it: an easily transported source of power without the limitations of batteries: just use a larger gas tank.

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jwax
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Re: voltage regulator circuit

Post by jwax » Thu May 26, 2005 12:16 pm

Have you considered solar cells on the wings? Not as primary power, of course, but to keep your batteries topped off, and to a minimum their weight. You'll want the highest watt/weight ratio.

onekill
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Re: voltage regulator circuit

Post by onekill » Thu May 26, 2005 12:20 pm

good Idea about the solar cells
and yes they do have generators that can be placed on the engine

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