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  • 24v DC 7 Amp PSU question

    Hi All,

    I am new to anodising, very new in fact as I only tried for the first time yesterday...

    I am using a constant voltage 24v DC 7 Amp supply and I can control the output current by using a 15 Amp motor speed controller and have had surprisingly good results, now I assume I am dropping the voltage as well as current when I turn the dial down however I only have one digital AVO and I am rather keen to keep an eye on the current having burnt off a wire from my rack to test piece yesterday.. (Oops!)

    My question is what is my current density, my view is it is in the region of 25 Amps as it is a 24v DC PSU but I could be very wrong....

    Can someone point me in the right direction please.

    Many thanks

    David
    /d

  • #2
    Re: 24v DC 7 Amp PSU question

    Current density is a number that you choose... go for 6 amps per sq. ft., so;
    Measure your total surface area of the parts in sq. ft. (144 sq. in. = 1 sq. ft.).
    multiply by 6.
    Rack your parts and hook everything up.
    Turn the ps all the way down and then turn on.
    Slowly turn up to your calculated setting.
    You should have an amps meter, and a volts meter so that you can monitor both. You can pick up panel meters off ebay pretty cheap.
    You'll need to watch the amps and keep them steady at your setting... they will wander.
    Make notes of what the volts are doing at measured intervals. I use a dry erase board with start and end time, set amps, and intervals of volts and tank temperature. Intervals are beginning, 5 min., then every 15 min to end of run.
    I do things.

    Comment


    • #3
      Re: 24v DC 7 Amp PSU question

      I managed to rig up a voltmeter as well as current (Both digital and should be accurate) I was anodising with a 12.5v/2.2 Amp supply and the results with black dye are superb. No doubt I will have more questions however with luck I will find them on the forum.

      Many thanks for you assistance

      David
      /d

      Comment


      • #4
        Re: 24v DC 7 Amp PSU question

        If you are running an acid ratio of distilled water 3:1 battery acid, and using LCD method, working the numbers backwards this is what I got.
        If your peak voltage was 12.5V you had roughly a 5 ASF CD.
        You ran 2.2A set amperage, making your parts run 63.4" square surface area.
        IF these backwards calculations are close, it is why you had a positive result.
        You need to know tank temp - over 70* will start problems. Size of the part in surface area to know how much current to use. 24V will allow you to run up to 9ASF. Knowing the voltage will tell you if a run is going alright but not as important as maintaining a set current.
        SS

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        • #5
          Re: 24v DC 7 Amp PSU question

          Acid concentration was 3 litres of demin to 2 litres of 36% Sulphuric acid which were the instructions I was given in the kit (Gateros) So a 1.5:1 ratio. I did not measure the SG once the tank was filled as I do not have a Hydrometer.

          I calculated the surface area at 61" square inches however the parts were incredibly complex so I may well have been a couple of percent out. It looks like my PSU will give me a maximum of 24v DC and 7.7 Amps and as I ramp it down both current and voltage are reduced hence the 12.5vDV@2.2A

          I live in the UK where warm days are few and far between so the ambient temperature should be sub 65F most of the time which helps to keep things cool. What happens to the anodising process when the electrolyte temperature is say 50F and again what happens when it goes above 70F, I assume temperature has an impact on either anodising quality or time?
          /d

          Comment


          • #6
            Re: 24v DC 7 Amp PSU question

            the Gateros kit is a different process to whats used on this forum.
            give them a call, they are very helpful and will guide you through their process.
            "A stupid man's report of what a clever man says is never accurate because he unconsciously translates what he hears into something he can understand.
            Custom Anodising

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            • #7
              Re: 24v DC 7 Amp PSU question

              I was more interested in the practice and operation behind the anodising process. Gateros sold the basic provisions required to get me going which was handy as it provided a one stop shop for me however I would hate to have to ring the chap up every time I have a minor question hence seeking advise on a forum. To the best of my knowledge we do not have a UK anodising forum I can ask general questions on.

              The good news is the next batch of black anodising has yet again returned stunningly good results.
              /d

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              • #8
                Re: 24v DC 7 Amp PSU question

                Higher acid concentrations = less resistance, so lower voltages.
                Lower temperature = higher resistance, so higher voltages.
                If you go over 70F (even the micro-layer of ano bath at the parts surface), you may get desoluution (ano being eaten away as ano is being built). That is why agitation and temperature control are important.

                We strongly encourage you to get on the same page as all of us, which means 1:3 battery acid/water, CC power source, ano-specific dyes and chemicals, etc. etc.

                BTW, you have found both a source for chemicals, and a forum for anodizing which is UK based: Caswell Europe
                I do things.

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