Date   : Mon, 16 Oct 2006 16:32:16
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Econet clock power requirements

Wright, Chris wrote:
> I have an 'american' Econet clock (metal shell) which seems to be
> working fine, even though it was supplied without psu, meaning I had to
> guess the input voltage.
> Following the lead of the BeebMaster, I used 9v as per an identical
> situation that he found himself in, and has documented on his site.
> I am a bit concerned that if this is not the correct voltage I may be
> drastically shortening the life of the clock ? In the absence of any
> correct power requirement info, should I drop the voltage down to the
> lowest voltage at which everything still seems to be working normally ?

Depends on whether you're worried about voltage, or about current-supplying
ability :-)

I'm pretty sure that these things regulate down to +5V internally. I thought
it was via the venerable 7805 regulator, but in the photos that Ian referenced
it looks like it might be some other LM-series regulator chip (albeit still a
3 pin device).

Anyway, looking up the specs for that regulator would be a good place to start
as it'll say what the maximum input voltage is. Somewhere around 8-9V is
probably about right though, although I expect it'll likely work as low as +7V
and as high as +12V (although at a shorter life).

Can't comment on current (and hence power), but I bet that regulator's not
designed to go much above 1A (and probably doesn't come anywhere close to that
under normal conditions anyway)

cheers

Jules