I wouldn't use a PC power supply for this. No matter what there age they
all are too finiky for this kind of work. This sounds like an atx power
supply that is even less suitable for general experimentation.
On Wed, 03 Dec 2003 10:54:49 +0003, the renowned "Jif"
Sure, you'd probably want the 12V output, right?
1) You usually need to load the 5V output with something like 1A
or the supply won't start properly. An old headlight will do
if you don't have an appropriate power resistor laying around.
2) The ATX supplies need the PS_ON (usually GREEN/14) wire
shorted to ground (BLACK eg. 15) to get them to start. AT
supplies (single row connector) don't need anything.
If you blow it up, it's only worth a few bucks.
"it's the network..." "The Journey is the reward"
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I wouldn't think so. You need some control over the output. The one I
use can be seen at
I managed to find all the parts surplus.
Sure. Just be careful and take off rings and watches when playing with
high current. I saw some nasty films shown to me many years ago.
Still keep a hand in a pocket when working on AC -
I'd keep the connector on - and if you need to, take out the pair you
Remember - determine the current you need and the voltage range.
is limited with a rheostat in series - a high power adjustable resistor.
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer firstname.lastname@example.org
Wrong! (At least the Variac part.) PC power supplies (all the
way back to the original IBM-PC) are switching mode power supplies.
They can keep working producing the same output voltage through a fairly
wide input voltage range, and then just totally shut down at some
specific lower voltage, so the suggested Variac will do you *no* good.
With a brute-force power supply (transformer, rectifier and filter
only), it would work quite well for adjusting the output voltage and
current, but with a switching mode supply, or even an actively regulated
one, you have electronics fighting you the whole way -- electronics
whose design function is to keep the output voltage constant no matter
In addition, the older switching power supplies have problems
producing adequate 12V output when the 5V is not loaded to a certain
level. Some systems even had a load resistor to hang on the 5V when only
one hard drive was installed, or no hard drive and only a floppy drive,
which draws a *lot* less current.
However, if your power supply includes a 3.3V output, it is
rather newer than that style.
So -- they are great for driving a lot of current at constant
voltages, but not really that good for plating, where you need to adjust
the voltage to maintain a current proportional to the square inches of
whatever is being plated. (So many amps per square inch.)
The *ideal* thing would be a power supply with an adjustable
current limit, so it will automatically adjust the voltage to maintain
the pre-set current, if possible.
For this sort of thing, I tend to use old lab power supplies,
with meters to monitor both the voltage and the current, and the
afore-mentioned current limit feature. What I use is a 0-36V 0-5A power
supply from about the late 1960s or early 1970s, made by Power Designs.
I used to use them at work, and snapped one up when I saw it at a
hamfest. This one even has a built-in Variac to keep the difference
between the set voltage output and the raw internal power down enough
to minimize internal heating.
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