Electrochemistry Variable power supply.

[caustic]

Hi all, after reading some of the threads in this forum I am wanting to try my hand at electrochemistry, My main objectives will be an electrolytic silver cell, sulphuric stripping cell, and even just anodizing titanium. Now from what I can understand these procedures all utilise different voltages/amperage. I am looking at buying a variable power supply. What Voltage/amperage range should I be looking for to cover all my bases. I am in Aus, but if anyone has any brand recommendations or brand warnings It would be appreciated, thanks Michael..

 

[bswartzwelder]

I purchased a laboratory type power supply from a seller (don't remember which one, sorry) on eBay. It wasn't cheap, but was the most affordable one I saw. It can be set to deliver any voltage from zero to 30 volts (continuous) and can also be set to deliver any amperage from zero to 10 amps (continuous). In hind sight, I wish I would have spent the extra money on one that could deliver 30 amps. Don't like running equipment at 100%. However, it will be run at 100% for short times probably less than 2 hours at a time. I feel these are better than the car battery chargers because most car battery chargers only have a half wave rectifier. Even the better ones with a full wave rectifier don't have the filtering capabilities and therefore the voltage and current drop to zero 120 times a second. This is a lot of variation in the output and is called ripple (not the drinking type). A constant voltage and constant current are better for electroplating, but are not absolutely necessary. Many of the forum members successfully use the car battery chargers. One other disadvantage of the car battery charger is that it is not variable or regulated. You get what you get. If you short it out, it's possible it will be damaged, but if parts are available, they should be easy and inexpensive to repair. Laboratory power supplies usually have voltage and current limiting circuits, so they stay where they are set. Having said that, in an electrolytic cell, once the gold has been reverse electroplated off the parts you are stripping, the current drops way down. This would be seen on the (analog) ammeter on most battery chargers. I haven't used mine yet for strpping gold from scrap, but both meters are digital, and I'm not sure how they will react. I will most likely add an analog ammeter in series with the load and an analog voltmeter across the load until I see some results. Don't know if this will help, but there are a few subjects I know a little about. Any questions, ASK away. If I don't have the answer, there are plenty of others here who will.

By the way, when time permits, I'm going to try to build a reverse electroplating cell similar to the Shor Simplicity system. I have some ideas for design changes which may make it more efficient.

 

[caustic]

Thanks for the reply, Yes the first thing I did was search ebay and I almost made the mistake of picking up a unit with a 0-30 volt range but limited to 5 amps.

 

[element47.5]

First, decide whether you want meters on the supply or not. They are nice but not necessary if you are on a budget, or, if you are starting up and don't yet know whether you want to go "all in". It's perfectly fine (in my book) to buy a multimeter (they are cheap now, under $20) and use it to monitor volts, and, when not using it for chem purposes, then it's a meter which useful elsewhere. This is NOT that good for measuring current...because current measurements require interrupting the circuit and thus you would need a means of doing that. A connector. It would be perfectly valid to chop off the disk-drive cables from the power supply you use for the 3.3 volts and use one of these (actually...you would need a male and a female, and ideally, you need four to set up a little deal so that you could insert (or not) your meter.)

Most electrochemical processes use less than 5 volts, but depending upon the size of your "tub" they might need a fair amount of current, I am calling ten amps or more a fair amount of current.

If you want to go the cheapest, a converted PC power supply can be FREE and can supply 3.3 volts at 20+ amps. Pretty nice. And if for some reason you blow it up, well, the next one is free, too. Kadriver has used these with great results and you should be able to search (by author) for his EXCELLENT posts re: silver cells. To make one work, you have to figure out how to 1: Short those two pins that represent the "on-off" switch; and 2: Provide a load so that power supply can start and run. This is entirely typical of a switching power supply. The load is just a resistor that convinces the power supply that "there is something there".

Point being, this has been done and it works fine. Google "Convert Computer ATX Power Supply to Lab Power Supply" or 'Bench' Supply and you'll find multiple articles showing just how to do it. Not difficult at all.

If you don't like that, you can often buy a surplus Lambda supply of a type that goes in the back of some other piece of gear. Here's a 6 volt one that can put out up to 19 amps. $10. Of course there is the issue of shipping same to Australia, but there are zillions of these out there. Other brands are Acopian, Power One...but the Lambdas are bulletproof and probably most common.

http://www.ebay.com/itm/Power-Supply-Lambda-LM-E6-115-VAC-to-6VDC-/130841372110?pt=LH_DefaultDomain_0&hash=item1e76c0e5ce

Keep looking for surplus Lambda or Kepco or Sorenson or Acopian....maybe you can find a nice rackmount one with meters. Meters are definitely nice, but once the item looks like a real piece of equipment, with fancy meters, then folks generally want money for them.

The PC supply works great. Don't diss it. Check out kadrivers' posts.