Re: [CAD_CAM_EDM_DRO] lm317

On Saturday 05 June 2004 08:08 pm, afogassa wrote:

> Hi All,
> I need to get 24 and 5v from the same transformer,I had in mind that
> I could set one lm317 to 24v. than feed another lm317 and set that to
> 5v. The 24v would feed a relay card and the 5v a pic 18c452
> I've searched on the lm317 application notes and haven't found any
> thing like it,will it work?

Yeah, it'll work, depending. What you need to watch for with any kind of a
regulator like that is the power dissipation. Dropping from 24V to 5V is a
drop of 19V, which means that even pulling only half an amp, say, you'll
still be kicking out 9 watts as heat. If you *must* go with this setup then
I'd suggest a dropping resistor at the input of the second regulator, to get
that down some. But why *must* you use only one transformer?

The big issue here is how much current you need at each voltage. Can you nail
that down?