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[Newbie] Supplying power to a project

I one of those folks who knows enough to be dangerous. I have a good grasp of a lot of basics, but I'm missing a fundamental piece that's really important for a project I'm doing.

I've built a nice little FM transmitter kit which I'm putting in a nice wooden case which will have an iPod dock on it. The transmitter works great. It runs best on 12V.

The iPod will charge at 12V. This, of course, could be a really nice way to both be broadcasting and charging at the same time. That's my intention.

I see the iPod will take 12V on the firewire power connectors, and it says "1A Max". The basic piece of information I'm missing is: I want to supply ample power to the iPod and transmitter. Do I need to worry about supplying too many amps? Is amps just a measure of what the device will draw and/or use? And how can I know how many amps the transmitter is using?

And I ask all this fearfully, knowing that I may not even be asking the question correctly.

Can anyone help me understand this, or point me to someplace I can figure this out?

Thanks much!

P.S. I already have some nice links to simple voltage regulators to help know I'm getting the right voltage there.

Reply to
kpmartin
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It is not the amps you have to worry but the switcher noise. The cheap transmitters are sensitive to the supply, especially when a switcher is used. You are never able to filter the noise introduced by the switcher, meaning the switcher noise is going to be broadcast.

Rene

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Ing.Buero R.Tschaggelar - http://www.ibrtses.com
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Reply to
Rene Tschaggelar

it

That would be the *maximum* current drawn - probably when fast-charging the battery(?).

ample

supplying

Yes - overkill is not better, it is just waste!

You can buy/design a 12V, 1A linear supply without too much trouble. At 3A .bob..bob.. maybe a switcher is necessary and then you will have real trouble filtering the noise out (after having real trouble with the design and layout).

What you *do* need to worry about is overvoltage - it is sad to fry an ipod due to some power supply bug! A quick fix could be to use a Transorb on the output of the supply so if it does blow up, the tranzorb will short the supply, cause the fuse to blow and save the Ipod.

using?

Measure it - one would expect that the transmitter be less than 50 mA; unless you want the visit from the "proper authorities". ;-)

Reply to
Frithiof Andreas Jensen

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