Pls F1 me: Electroplating using computer power supply

hi

i have an old pc (member dos days) which is written on it: AC input:

151/230vac 8A/4A DC output 20A@3.3v, 30A@5v, 12A@12v

is this PS usable as power supply for electroplating for fun and learing.

Thanx in advance

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.

Best regards, Spehro Pefhany

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.

Ted

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 want.

Remember - determine the current you need and the voltage range. Current is limited with a rheostat in series - a high power adjustable resistor.

Martin

Go for it, put the appropriate size variac ahead of it and you've got it made. I've used every sort of DC device including car batteries for plating.

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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 what.

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.

Good Luck, DoN.