Power supply problem - Anodising

[Chevalier]

Hi, hope someone can help...

I'm trying to anodise some parts off my bike, but I have run into some problems providing enough current. Firstly there is an Anode and a Cathode submerged in a water/sulphuric acid/sodium sulphate solution, for the cathode I am using a bar of aluminium and the anode is the part to be anodised.
I started by using a car charger(can do 0-8 Amps), that gave about 1-3 amps going through the part to be anodised, this was way to little current from what I’ve read, so I connected up two computer power supplies in parallel(together they can do a max of 18 Amps at 12V), and put these in series with the car charger, this boosted the car charger to about 3-5 Amps, but this is still not enough. I tried to use just the two computer power supplies on their own, but they don’t work, they only use 0.2 Amps.
I managed to get a power supply rated 10-14 Amps, I connected this in series with the two computer power supplies, the current kept rising until it reached 18 Amps and then the safety clicked in and turned the charger off. I would like to just use the computer power supplies, does anyone know why they are turning off when they are on their own but work when in series with a charger? And is there any way of getting them working on their own? I’ve also tried to use a load when using the computer power supplies, this had no effect.
The parts come out pink instead of red, but earlier I did one that was red in patches, I noticed that this time the part took more than normal current, so if I can get enough current the parts should look great.
Thanks for spending the time to read that, any help would be great.

 

[marcusgunby]

A car battery will provide alot more current than the charger but i would be very concerned about how you would control the amount of current.It sounds a risky thing to play with-acids and large currents.

 

[Jaybird]

http://www.focuser.com/atm/anodize/anodize.html#top

 

[Person8]

To add to the max current and keep the voltage the same, power supplies need to be hooked up in parallel. Positive to Positive, Negative to Negative. If hooked in series the current will not increase, the voltage will. Try your supplies in parallel and see if the results are any better. A car battery can provide up to a couple hundred amps, which may be a bit too much.


Larry

 

[Chevalier]

I understand that is a little on the dangerious side, but i am doin' it all safe!
The problems i am having with the computer power supplies is that they don't do anything on their own, they just swithch off, but they are in parallel. When i hook them up to the charger in parallel, the charger jumps forom 0-8Amps then turns off then jumps to 8 Amps again, and so on. I am trying to find out why the computer supplies won't work on their own, like is there a safety device, or a bit of circuit i can over ride.

Thanks

 

[n8MX]

I think the problem with hooking the supplies/charger in parallel may be that the voltages are not matched. The charger puts out more than 12V - it has to in order to charge 12V batteries. The PC supplies put out closer to a regulated 12V (since the demands of the PC are much more precise than a car battery). When you hook these up in parallel they are essentially fighting each other... for example the charger is trying to raise the voltage of the PC supply while the PC supply is trying to lower the voltage of the charger. This can take a ton of current and is probably the reason that the current-limit in the PC supplies is tripping.

I think maybe a bigger battery charger is in order.

Andy

 

[Chevalier]

ok, thanks, I'm now looking into other means of powering it, i was looking at a truck charger for €600---a LITTLE on the high side!!! using a car alternater was suggested...

Thanks again