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Electrolysis Power Supply from Re-purposed Computer Power Supply

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Blog entry by ajosephg posted 07-09-2011 09:33 PM 7409 reads 10 times favorited 12 comments Add to Favorites Watch

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.

-- Joe



12 comments so far

View SPalm's profile

SPalm

4930 posts in 2626 days


#1 posted 07-09-2011 10:11 PM

Great job. You done good.

That is a what is called a switching power supply. The regulation is done by high speed chopping up of the incoming 110volt, going through inductors and FET switches, and then smoothed back out to come to you. The only reason I mention this is that is why it is so small and light, considering the amount of power it can supply. This also makes it very energy efficient, as they don’t use the old very large heavy transformers of a non-switching power supply. Another benefit is that it is short circuit proof. i.e. You don’t need a fuse on the DC side. It will shut itself down if it detects a short, and come back when the short is removed.

Steve

-- -- I'm no rocket surgeon

View ajosephg's profile

ajosephg

1860 posts in 2305 days


#2 posted 07-09-2011 10:16 PM

Thanks, Steve. I knew it was a switcher, but wasn’t sure about over current protection. Now I can rest easy.

-- Joe

View KayBee's profile

KayBee

1020 posts in 1990 days


#3 posted 07-09-2011 10:38 PM

Cool! Another use for the power supplies I have sitting around.

-- Karen - a little bit of stupid goes a long way

View David Grimes's profile

David Grimes

2072 posts in 1384 days


#4 posted 07-09-2011 10:39 PM

That is a very nice, clean and well thought-out re-purposing.

I did this down and dirty back in 1996 to clean up some automotive parts, but after the few bath I threw it away (and haven’t needed it since). I’ve got 6+/- laying around in my computer junkyard boxes. But the binding posts, switch and dummy load makes this a keeper.

Impressive.

Just put a vented wood case around it, some non-slip feet and sell it to me ;=)

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View MShort's profile

MShort

1729 posts in 2162 days


#5 posted 07-09-2011 10:44 PM

How cool is that. Thanks for sharing and doing a great job of the narrative with the pics.

-- Mike, Missouri --- “A positive life can not happen with a negative mind.” ---

View Grumpy's profile

Grumpy

19693 posts in 2595 days


#6 posted 07-10-2011 01:07 AM

Very clever use of old technology Joe.

-- Grumpy - "Always look on the bright side of life"- Monty Python

View TechRedneck's profile

TechRedneck

746 posts in 1601 days


#7 posted 07-10-2011 02:07 AM

I was just posting on another thread about electrolysis. This is a nice idea, Thanks for posting.

-- Mike.... West Virginia. "Man is a tool using animal. Without tools he is nothing, with tools he is all.". T Carlyle

View KTMM (Krunkthemadman)'s profile

KTMM (Krunkthemadman)

973 posts in 1937 days


#8 posted 07-11-2011 10:34 PM

I have seen several methods of doing this, but I believe you have just put out the most simple one to follow.

-- Practice does not make perfect. Only perfect practice makes perfect. Vince Lombardi

View Bertha's profile

Bertha

12951 posts in 1437 days


#9 posted 07-11-2011 10:35 PM

I’m very impressed by this, Joe. Bringing electrolysis to the masses! I build computers, so I’ve got at least 1/2 dozen of these lying around. Bravo!

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View ajosephg's profile

ajosephg

1860 posts in 2305 days


#10 posted 07-11-2011 10:43 PM

I appreciate those kind comments.

Thank you

-- Joe

View David Grimes's profile

David Grimes

2072 posts in 1384 days


#11 posted 07-12-2011 02:20 AM

Bertha, See post #42 on your own thread in case you missed it in all the #8 excitement: http://lumberjocks.com/Bertha/blog/23687

However, Joe has taken it to the next several levels with dedicated dual voltage/amperage 5V/ 22A and 12V/6A posts and the lighted switch as well. Not to mention that he has (compared to my old rig) cleaned a rats nest up the RIGHT WAY !

Joe, now you know what I think about your project. If I wore a hat, it would be off to ya !

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View Eric's profile

Eric

185 posts in 1255 days


#12 posted 07-18-2011 04:31 AM

I did that very same project a while back. However, my switch the yanking the power cord out of the socket.

I’ve used mine for testing trailer lights without the truck. Its handy to have 12v available from time to time. Looks good!

-- Eric

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