[sdiy] Power distribution board

[Mike]

> On Saturday 04 April 2009 01:30:00 pm David G. Dixon wrote:
> > This leads to my next question:  Presuming that most have only +/-15V
> > supplies in their modulars, what is the best way to handle digital
power?
> > I've only breadboarded circuits with TTL chips powered by a 7805
reducing
> > +15V to +5, and was startled (and a little frightened) at how hot the
> > regulator ran.  I'm not sure I'd want anything that hot on any of my
> > lovingly hand-crafted boards!
>
> That's also fairly wasteful of power...
>
> Commercial gear that I've seen that uses those kinds of levels typically
seems
> to use a separate winding on the transformer (though for homebrew stuff
I'd
> see a separate transformer as being easier to find with suitable outputs)
and
> rectifier / filter circuit so what's going into any regulators isn't all
that
> high.
>
> > I was thinking I would probably opt for just putting the +15V through a
> > simple voltage divider to get +5V and be done with it, but I'm
wondering:
> > is this anathema?  Does one find oneself excommunicated from the fold
for
> > such heresy?
>
> Dropping 10V for a 5V output is wasting twice as much power in the
regulator
> as the load is using,  which is truly horrible from an efficiency
standpoint.
>
> I hear that there are chips that make switching regulators real easy these
> days,  too.
There are very nice switching power supply modukes available too, they
solder (orplug) on to the board. You can get ones that drop 15 or more to 5
and ones that will make a +/- 15V supply from the 5 Volt rail in a digital
system I've used some that had an insrumtation quality output, (read 'very
clean'), and some were very noisy, so it pays to read the spec carefully.

HTH

||\/||ike


>
> > > -----Original Message-----
> > > From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> > > bounces at dropmix.xs4all.nl] On Behalf Of Roy J. Tellason
> > > Sent: Saturday, April 04, 2009 10:14 AM
> > > To: synth-diy at dropmix.xs4all.nl
> > > Subject: Re: [sdiy] Power distribution board
> > >
> > > On Saturday 04 April 2009 05:50:29 am Julian wrote:
> > > > Somthing ive wondered -
> > > >
> > > > Regulators are cheap - what about a power bus running over-voltage
and
> > > > then a pair of dedicated regulators for each and every socket on
that
> > > > bus?
> > > >
> > > > Would that effectivly isolate every module?
> > > >
> > > > (im thinking back to my old doepfer lfos thatlld modulate the
doepfer
> > > > vcos on the same bus...)
> > >
> > > That was the approach taken for the real early S-100 bus computer
> > > systems, with the power buses being 8V, and +/-16V,  which were
typically
> > > regulated down to 5V and 12V on each board.  Some boards had to have
> > > multiple regulators for the 5V,  and there were heat dissipation
issues.
> > > Later systems put jumpers in place of the regulators and used
switching
> > > power supplies instead,  though I've not much experience with them.
> > >
> > > But yeah,  I'd say this would provide a lot of isolation.