One of these days I plan on using electrolysis to remove the rust on my modest antique tool collection. However, I don’t own a battery charger and see no need to purchase one, so I decided to use the power supply out of an obsolete personal computer. This is my story.
1. I ran an ad on Freecycle for an old computer. Within several hours I get a hit from a fellow with a late 90’s Dell Dimension desktop computer.
2. Removed the power supply and after a lot of head scratching decided to toss the remaining parts as opposed to storing them and then trashing them years later.
3. The power supply had about 9000 wires and connectors with no clue as to what they were for. A few hours of research on the web disclosed the pin outs for the connectors and their function. Also found an article on WikiHow titled How to Convert a Computer ATX Power Supply to a Lab Power Supply. I used the general principles in that article with several minor modifications. The major required mod is that a Dell power supply has different pin-outs and wire colors than the “industry standard” ATX power supply.
The +5v and +12v outputs are rated at 22.0A and 6.0A respectively which is more than adequate for electrolysis. All this in a 6×6x3.5 box!
4. i went on eBay and purchased: 10 ohm 10 watt resistor, 3 miniature binding posts, toggle switch, LED, and a 510 ohm 1/4 watt resistor. (I have 19 LEDs and 510 ohm resistors left over if anybody wants them.)
5. Took all the guts out of the power supply and drilled holes for the binding posts etc. in an area away from internal circuitry per following photos. I used super glue to hold the LED in its hole.
MODIFIED FRONT PANEL
INSIDE VIEW OF MODIFIED FRONT PANEL
CIRCUIT BOARD AND WIRING HARNESS REMOVED FROM CHASSIS
The following photo shows the circuit board and harness back in the chassis. Unused wires have been clipped, and the important wires have been connected to the front panel components. The black wire is ground and is connected to the black binding post, red is +5v, and yellow is +12v. The gray wire is connected to the center terminal of the switch. The pin out of the Dell power supply calls this connection PS On, and is active low. I.e. when grounded the power supply will turn on. The outer terminal of the switch is connected to the black binding post. The orange wire is connected to the 510 ohm resistor which in turn is connected to the anode of the LED. A piece of shrink tubing covers these connections and the resistor. The cathode of the LED is connected to the black binding post. The pin out of the power supply calls the orange wire Power Good If all the voltages are correct when the supply is turned on, the LED will be energized.
FRONT PANEL CONNECTIONS
The power supply is designed to shut off if the 5 volts doesn’t have a load. A 10 ohm resistor is connected to a red (5 volt) wire and the other side of the resistor to a ground wire to satisfy this condition. I used a chassis mount resistor and attached it to one of the heat sinks. I drilled the holes in the heat sink when I had the circuitry out of the chassis. (BTW – I used to work for the company that made this resistor. :))
DUMMY LOAD RESISTOR MOUNTED TO HEAT SINK
FRONT PANEL WITH POWER ON
FRONT PANEL POWER ON CLOSE UP
It works great on the bench. Haven’t made an electrolysis bath yet, but will be referring to Bertha’s blog on that subject.
In retrospect I wish I had wired in an in-line fuse in the +5 and +12 lines, although the power supply may have automatic overload protection built in. It does have a built in fuse on the supply line so it shouldn’t go up in flames should something bad happen. Not a hard job, but you should have a low wattage soldering iron and some skill in soldering.