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### Topic: <SOLVED> Another Noob Power Question (Read 830 times)previous topic - next topic

#### NobleNoob

##### Oct 18, 2012, 05:14 amLast Edit: Oct 18, 2012, 06:13 am by NobleNoob Reason: 1
If you start out with a regulated power source, say 35A of 12V from a converted ATX power supply

In a simple voltage divider as I understand it anyway,

R1              R2
+12V        o----\/\/\----o----\/\/\------o  GND
V1               V2

How do I find out what values for R1 and R2  if  V1 = 12V and V2 = 7.5 @ 2.0 Amps

R1 = ?
R2 = ?
V1 = 12V
V2 = 7.5V

And since the V1 = regulated 12V and isn't supposed to fluctuate (too much)
would I not get a fairly constant value from V2 ?

This would allow for powering a couple of legacy devices that require a regulated 7.5 V as well as powering the arduino itself at 7.5V instead of 12V making arduino regulator work cooler.

I'm gonna burn up so much stuff... better tripple my parts order!

Thanks guys...

#### oric_dan

#1
##### Oct 18, 2012, 06:06 am
You can't use a voltage divider to power a load, since the voltage out depends upon
the load current. IE, the usual formula for the v.div assumes no load current.

One solution is to use a voltage regulator, but something like 7.5V @ 2Amps is not easy to
produce. You should probably look for some kind of dc-dc converter that will push 2A
and where you can set the voltage out.

#### NobleNoob

#2
##### Oct 18, 2012, 06:13 amLast Edit: Oct 18, 2012, 06:14 am by NobleNoob Reason: 1
I knew it!, I just knew it, just like that dream of winning the lottery, so real, so vivid, until I woke up

I havn't gotten my starter kit yet and am going nuts

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