First Post from Newbie

Discussion in 'The Projects Forum' started by Moosebreath94, Dec 29, 2008.

  1. Moosebreath94

    Thread Starter New Member

    Dec 29, 2008
    4
    0
    I have a small hobby anodizing line set up in the basement, 12-24VDC@2-5A.

    I would like to do some "Type III" anodizing, 48-70VDC.

    My power supply is a battery charger and two 12V marine batteries. My control is a variable 350W resistor.

    Rather than buy 2-3 more batteries, I think that I would like to use a voltage multipling resistor network. I remember seeing plans years ago, always with the warning of how high the voltage could get with these networks. I have also seen commercially produced (cheap) multiplier circuits for small ozone generators (KV) that plug into a autos cigarette lighter socket.

    For the life of me, I can't find plans anywhere for a voltage multipling resistor network. Does anyone know of plans, theory, or a reasonable alternative that might give me 2-5 A?

    Thanks,

    Jim Herbert
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,641
    2,344
    Hello,

    You will never manage it with resistors.
    You will need someting like an DC-DC inverter.
    http://www.maxim-ic.com/cookbook/powersupply/
    The maximum current in the examples of this page is 64 Volts at 0.35 A from an 11 - 14 Volt source.

    Greetings,
    Bertus
     
  3. duffy

    Active Member

    Dec 29, 2008
    44
    0
    He might be thinking of a Marx Generator, that uses a bunch of resistors and would generate plenty of ozone!

    Not something you would want to use for anodizing, though.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,641
    2,344
    Hello,

    For hardcoat you will need quite a current :
    Type III: Hard Coat Anodizing

    (Low Temperature, Hard Anodizing)

    Sulfuric acid anodizing has been defined as “an electrochemical process that intentionally forms a porous anodic oxide on aluminum”. This oxide, an integral part of the metal, is formed when a current is applied to the aluminum parts in a sulfuric acid anodizing bath.
    Type III (hardcoat) anodizing is an anodizing process that forms an extremely hard, abrasion resistant, porous oxide on aluminum. It is generally referred to as an “engineering hardcoat” due to the fact that the oxide has been found to be suited for applications where the hardness and increased oxide thicknesses are an advantage. Aluminum cookware, military applications and a myriad of other uses have made Type III anodizing very popular.
    Type III (Hardcoat) anodizing differs from the typical Type II room temperature anodizing in a number of ways:
    The anodizing bath parameters for Type III (hardcoat) anodizing are similar to type II (room temperature) anodizing in that the acid and aluminum concentrations can be virtually the same. The difference becomes apparent when you consider the other operating parameters.
    Type III anodizing is performed in a sulfuric acid bath containing 180-200 grams per Liter of acid and a small amount of dissolved aluminum. The operating temperature is controlled between 28-32º F but in some instances an acceptable oxide can be achieved at slightly higher temperatures. Current densities can range from 24-40 amps per square foot (ASF), but commonly are run at 24-30 ASF.
    The power supply is a DC rectifier. The aluminum part being anodized is made the anode (or positive pole) in the system. The most efficient cathodes (or negative pole) are 6063t6 aluminum.
    Current is applied to the system for a prescribed time, and at the desired current density to achieve the oxide thickness required (oxide thicknesses can range from 0.7 mil to 3.0 mils). The resulting porous oxide can then be colored or sealed but limitations on final color will determined by the oxide produced and color used.


    Source : http://www.anodizeusa.com/anodizing-systems.php


    Greetings,
    Bertus
     
  5. Moosebreath94

    Thread Starter New Member

    Dec 29, 2008
    4
    0
    Thanks for your input Bertus.

    I currently run 16 ASF so an increase to 24 ASF would not be too large, considering the size of my very small tank. I usally run about 2A with both racks full, 18-20 in2. 3-4 A (50Amp Meter) should be tops (for this tank).

    Perhaps you are right about the resistor network. Maybe I was thinking about AC doublers,triplers,and so on. It just sticks in this old brain, I know I have tried unsuccessfully to find them before.

    I guess its time to either buy some batteries or start digging out old large transformers and caps that have been heretofor classified as boat anchors.

    Thanks again,

    Jim

    Just because the phone net manager gave be the Novice Test 1 day late (31 days after code test) 30 years ago doesn't mean I dislike all Amatures.

    When your in a little sailboat in the middle of a large ocean you still reach for the SSB, or the QRP CW Rig (Heathkit w/ VFO.
     
  6. leftyretro

    Active Member

    Nov 25, 2008
    394
    2
    Have you considered using a AC variac transformer wired to a full wave bridge rectifier. It might be the simplest approch as long as you have the means to measure and monitor the output voltage and current. The main advantage is that there would be no waste heat generation and a decent savings on your monthly electric bill.

    Here is a typical 10 amp output Variac:

    http://www.allelectronics.com/make-a-store/item/SC-10M/10-AMP-VARIABLE-TRANSFORMER/-/1.html

    Here is a typical diode bridge rectifier module:

    http://www.allelectronics.com/make-a-store/item/FWB-254/25-A-400-PIV-BRIDGE-RECTIFIER/-/1.html


    Lefty
     
    Last edited: Dec 30, 2008
  7. Moosebreath94

    Thread Starter New Member

    Dec 29, 2008
    4
    0
    Thanks Lefty,

    The variac looks very nice. Is it an autotransformer? I started getting shocks from a large surplus variable autotransformer that I used to use as a power supply, and junked it long ago.

    The variac my be a nice ultimate solution if I continue to due Type III anodizing but I think that it is a little too expensive for me right now.

    Nice bridge.

    Thanks Again,

    Jim
     
  8. Moosebreath94

    Thread Starter New Member

    Dec 29, 2008
    4
    0
    Lefty,

    Yes, a Variac is an autotransformer. I just bought one from the surplus place, 10A $54, no enclosure. I hope I don't light up the anodizing bath like I did the plating bath years ago, a short means line voltage in the tank.

    I am not too concerned about power supply voltage regulation but any circuit ideas for current regulation?

    Jim
     
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