[ILUG] OT: stepping down from 12v to 9v

[Declan Moriarty]

On Wed, 2006-05-03 at 10:20 +0100, Niall O Broin wrote:
> On 1 May 2006, at 20:58, Declan Moriarty wrote:
> 
> >> 9V is perfect for feeding a 7805 but it's an 'odd' voltage for a  
> >> switch to run
> >> on directly, so worth checking.
> >
> > Is this still going around?
> >
> > 7809s are rare & old.
> 
> Oh dear - so my electronics knowledge is getting obsolete - bummer.  
> But why did you mention this? You're the first to mention 7809s in  
> this discussion.
> 
> > They standardised on 7805, 7808. Get the 7808, put approx 500 ohms  
> > (some) or 1K (the rest) in the GROUND pin and you have 9V.
> 
> That's cute - how are you meant to know which to to use? Put in two  
> 1Ks || and measure the output, and if it's not 9v, snip out one of  
> the 1Ks ?
> 
> 
> Niall
> 
> P.S. I know it was marked [OT] from the start, but this has gone so  
> far OT it's in danger of straying back ON topic somehow.
> 
Mebbe the 7808s run on linux ;-)
-- 
        With Best Regards,

        Declan Moriarty.