PSN-L Email List Message

Subject: Re: computer power supply
From: meredith lamb mlamb1@..........
Date: Wed, 05 Jan 2000 11:19:27 -0800

Christian Parker wrote:

> Has anyone here ever tried to use the power supply from an old PC to power
> their seismometer electronics?  I have one laying around so I was going to
> give this a try.  The power supply outputs +12vdc and -12vdc from one of the
> connectors that normally connects to the motherboard.  The pinouts of this
> connector are as follows:
> Pin   Name    Color    Description
> 1     PG      Orange   Power Good, +5 VDC when all voltages has stabilized.
> 2     +5V     Red      +5 VDC (or n/c)
> 3     +12V    Yellow   +12 VDC
> 4     -12V    Blue     -12 VDC
> 5     GND     Black    Ground
> 6     GND     Black    Ground
> I'm wondering if this power is suitable for powering op amps?
> Christian Parker
> Boulder, CO
> cparker@...............


I'am sure I'am stepping into this subject where I don't belong,
but from my recollection from my brother, he has used these
very supplys for various electronic experiments.  Without
further details, I would think that they might need additional
power supply filters (capacitors) on the output.  Usually one
of the switching supply voltages is very limited on current
capacity; so, one would have to watch that.

Also "if" I recollect right.....(ahem), he stated that they are
better than the regular power supplys for transient protection

J.B. Saunders surplus there in Boulder also has a wide variety
of various types of power supplys there in Boulder; which might
work.  Of course the normal dual voltage supplys are somewhat
rare compared to the switching supplys in quanity.  One might
consider buying 2 regular transformer DC supplys to join
together to make the dual supply.

Radio Shack also has these cheap single supplys available.

The one remaining subject of power supplys is their regulation
performance.  Perhaps for amateur projects this can be
fairly passed over, as the normal use involved doesn't normally
cause problems where the sensor/s is coil/magnet and ampifier.

I actually used one switching supply on my Hall seismometers
for awhile, till it went kapoot.  (I still saw transient spikes....
mainly from the house furnace motor...ha)

Without knowing specifically what you are trying to do, its
hard to recommend something.  If you intend to lean toward
a coil and magnet affair; I would suggest buying from Larry.
His stuff works fine.  The trouble with home brew is that one
can usually end up spending more than buying commercially;
and, end up with something less than the quality they would
get if they had only just bought the stuff to begin with.

Yes....electronics and computers drive me bugs....ha.

Take care,

Meredith Lamb


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Larry Cochrane <cochrane@..............>