From: "Frank Bemelman"
References: <0001HW.B9D991AD000C5917163F7590@news.covad.net> <email@example.com> <0001HW.B9D9CD54001A5D15163F7590@news.covad.net> <0001HW.B9DAE8B7003F6E14163F7590@news.covad.net> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
Subject: Re: V regulator input cap size?
Date: Thu, 24 Oct 2002 23:10:01 +0200
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Organization: EuroNet Internet
NNTP-Posting-Date: 25 Oct 2002 14:31:21 GMT
"Lizard Blizzard" schreef in bericht
> Frank Bemelman wrote:
> > "Watson 'Atto Parsec' Name" schreef in bericht
> > news:MPG.email@example.com...
> >>In article <firstname.lastname@example.org>,
> >>email@example.com talked about...
> >>>>>The easiest way is a 7824 followed by 7812. Both should be
> >>>>>on a heatsink, you can use a single heatsink for this.
> >>>>I searched National's web site and they didn't have a 7824. But
> >>>>assuming that the 7824 has the same 35V maximum limit on input
> > voltage,
> >>>>he would still have the same problem, the unreg'd voltage would still
> >>>>exceed its limits.
> >>>It can handle 40V.
> >>That's still 9 or 10V short of what the unreg'd supply voltage will be
> >>the filter cap.
> > You accidently snipped away the part were the OP mentioned the *new*
> I didn't snip it, perhaps someone else did previously. But I have used
> transformers similar to these control transformers, and they put out
> about 42 volts at the filter capacitor. You have to remember that the
> transformer gives 28VAC at full load, so at much lower load, the
> secondary AC voltage will be substantially higher. And after
> rectification, it can go as high as 44 or so VDC which is about 31 to
> 32VAC times 1.414. If a regulator with 40V max is used, it will still
> have an input voltage that exceeds its maximum.
Makes sense, but I can only trust on what the OP tells me. Perhaps, on
one of those days, his mains voltage is higher, and he has another
problem to deal with....
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