[sdiy] Power Supply Design Questions

[harrybissell]

Hiya Maleman... (inline)

male man wrote:

> speaking of power supplies, i have am putting together
> a small system using a power one bipolar supply rated
> at 1amp.  the instructions mention a possible fan for
> air circulation.  this will be in an enclosed case
> with the modules.  im wondering how important this fan
> is.

If it does not get too hot... or there is sufficient volume inside the
case...
you are OK.  I'd consider mounting the power supply chassis to an outside
metal wall, or even fins so that you can get the heat to the outside.

> what if i am not drawing anywhere near 1 amp?

then you will NOT need a fan...

>
> what about the heat affecting vco's and such?

Yes, that can be a problem...and the more the temperature rises the worse
it gets. I'd even consider a partition in the case, or mounting the supply
externally
so that heat rising and circulating inside the case cannot affect the VCOs

H^) harry

> thanks
> for the help.
>
> skot
>
> --- patchell <patchell at silcom.com> wrote:
> > If you go here:
> >
> >
> >
> http://www.silcom.com/~patchell/powersupply/powersupply.html
> >
> >     You will find a scan of something I wrote up on
> > how to select a
> > filter capacitor for a three terminal type
> > regulator.  I generally allow
> > for 3 volts drop, sort of a margin of saftety.  You
> > have to remember
> > that there will be supply ripple going into the
> > regulator, and you need
> > to make sure that the voltage never goes below that
> > magic point.  So, it
> > is not so much the transformer you have to select,
> > but rather, the
> > filter capacitor.
> >
> > Scott Gravenhorst wrote:
> >
> > > Some questions I have:
> > >
> > > At what input voltage should a LM78xx or LM79xx
> > type
> > > regulator be run for minimum heat?
> > >
> > > I read in data sheets that 2 volts is the usual
> > value for
> > > dropout voltage (at 1A).
> > >
> > > Would this be the point (well, somewhat above it)
> > at which
> > > the regulator would heat up the least?
> > >
> > > Operated so, does this also mean using a
> > transformer with
> > > better current capabilities?
> > >
> > > Thanks all.
> > >
> > >
> >
> =========================================================
> > > - A smoking gun is one that's already been fired.
> > > - That which gets rewarded, gets done.
> > > - What good are laws that only lawyers understand?
> > > - Government: The other religion.
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> > questioned.
> > >
> > > -- Scott Gravenhorst | LegoManiac / Lego Trains /
> > RIS 1.5
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> > > -- FatMan: home1.gte.net/res0658s/FatMan/
> > > -- NonFatMan: home1.gte.net/res0658s/electronics/
> >
> > --
> >  -Jim
> > ------------------------------------------------
> > * Visit:http://www.silcom.com/~patchell/
> > *-----------------------------------------------
> > * Come to the Pacific Southwest DIY Meet
> > * April 12, 2003 10am-5pm
> > * Santa Barbara, CA
> > * http://www.silcom.com/~patchell/synthdiymeet.html
> > * for details
> > *-----------------------------------------------
> >
> >
>
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