If there's no chance of the full voltage appearing across the current limiter, you can reduce the number of transistors, but you need to consider the base drive current. In that case, with an absolute maximum dissipation of 115 watts for the 2N2955 (in a TO-3 case), you'll need 10 or more devices with lots of heat sinking (hopefully with a fan) to scale up OperaHouse's circuit. You don't say what the resistance of your load is, but keep in mind, with a 40 volt supply and a 30 amp limit, there's a chance that your limiter will dissipate 1,200 watts, mostly in the power transistors. I couldn't find the link on google directly. Since mine is just about a one-shot affair, it will be crude, but hopefully effective doing small parts.ĭoggone it. I have a back burner project doing anodizing but will be using a car battery and a large wire wound variable resistor for my efforts. It had something to do with anodizing telescope parts. I don't have immediate access to the info. Again, these can be switched in or out via parallel circuits.Īlso, out on the web, there is a rough calculation for the current/surface area of the part being anodized. Note that you will want to consider compression type connections for the wire used. If you want some more "robust" types of loads, one might want to salvage the reistance wires from old toasters, electric wall heaters, etc. Since you are running around 40V, you might want to string a couple of lamps in series for each load as you don't want to accidentially burn out a 12V lamp with 40V across it. Just a bunch of lamps and the current is adjusted (with the aid of a meter) by turning off and on various lamps. If you search the web for anodizing, you will run across one of these circuits. If this is a "one off" type and you don't feel comfortable with doing a large amount of engineering, you can have several automotive type lamps/headlamps wired in parallel with switches to do the current regulation and act as loads for you.