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topic 18282

Building a Power Supply


I am trying to anodize various parts from my motorbike, but I have run into problems. The power supply I am trying to use is a 12v, 0-6A, but you can't choose the amount of current, so everything I am trying to anodize is only drawing 1-2 amps, and it is not working, so I would like to build my own 12v adjustable power supply, that would be able to handle 0-40 Amps, but I can't find any schematics to do this, does anyone know what parts I need?


Robert Harrison
- Dublin, Ireland


If you only draw 1 to 2 Amps at 12 Volts with your 0-6 Amp supply, you'll only draw 1 to 2 Amps at 12 Volts with a new 0-40 Amp power supply as well.

I=V/R. The resistance of the solution and your wiring and geometry is a fixed value. If the voltage is a fixed value as well, the Amperage you will draw is the latter divided by the former.

Figure you will use no more than 20 Amps/square foot for anodizing. How big are the pieces?

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


I've done a few more things since I was here last. Firstly I have connected up 2 computer power supplies in parallel to give a max current of 18 amps at 12V. When used alone only .2 amps flows through the part, but I then connected these in series with the charger, this boosted the current to the point where the charger over loads and turns off for a few seconds, I left this going for a while and the current evens off at 4 amps. When the car charger is used alone on the same part, it starts using over 8 amps but then goes down to two amps, so by using the other power supplies I gained 2 amps. The part is about 3-4 sq. inch, also the part is only going a pink colour when dyed (it was in a red dye). This is why I am thinking that the current is insufficient. If anything is unclear please let me know, thanks.

Robert Harrison
- Dublin, Ireland


No disrespect intended, Robert, but I can't afford to spend the time to really try to understand the exact mechanics of how you've hooked three different power supplies together to try to make one, still improper, anodizing power supply :-)

You need to buy a proper power supply.

The drop off in current after startup is only to be expected as the anodized layer builds up in resistance, but it's not right to start up at high current. That is, you're not supposed to permit that high current flow initially.

If the area of the part is 3 to 4 square inches, you should not be anodizing at over about half an amp anyway. Yes, the pink color from a red dye is lack of saturation, and probably does occur because the anodized film is not proper. But whether that's because it was burned and destroyed by an overvoltage that caused 16x too much current too flow, or whether the film is too thin because your meters are totally out of whack as they try to monitor current coming in from three different directions is something I really can't tell. It's somewhat difficult to anodize, and to do it with unworkable power supplies is just a bad idea. Good luck.

Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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