I had never seen bleeder current before either. I took bleeder current to mean it was separate from the wall charger. I then rounded the current up, just to be safe, knowing that I would be well below that level. That’s how I got to 3amps maybe that is just way overkill and I could get away with a 1.5amp or 2amp rheostat.
Snake looking at your model rheostat you must have the 500ohm 100w rated at .447amp. Is that right? I have only plated two things so far. What is the most amps you push during any plating process you have done?
Your rheostat might be double what I had. Mine was 500ohm 25w and .22 amp!
Man I hope we can get to the bottom of this I want to start plating again soon. I loved the two parts I was able to too. It is addicting for sure.
For the home plating specialistAdam,
Bleeder current does not apply to your circuit because you are only using one leg and the wiper of your rheostat. The minimum current of .12 amps suggests a maximum resistance of 100 ohms. The maximum current of 1.0 amps suggests a minimum resistance of 12 ohms. Your resistance range is therefore 12 to 100 ohms. Since the max current flowing through the resistor is 1 amp at 12 volts, the minimum power rating will be 12 watts. I would double that because the current is only flowing in a few of the resistance windings so the heat build-up is concentrated around those windings as opposed to the whole area of the rheostat. You will need a minimum 1.0 amp current rating on the rheostat (double that for a margin of safety). It might be difficult to buy a 12-100 ohm rheostat so you could use a separate 12 ohm resistor in series with a 0-100 ohm rheostat. This would ensure a maximum current of 1 amp. regardless of the rheostat wiper position. This resistor could be rated at 20 watts. There may be 12 volt 1 amp automobile tail light bulbs that would work nicely as the second resistor. I should add that by using a second resistor (12 ohms, as noted above) you reduce the power rating requirement of the rheostat considerably, but you still need the same current rating. Wilf Wilf,
Glad to see you join in here. For clarity purposes, given what you have said above, the current rating of the rheostats are at a given voltage, correct? By that I mean a 1 am rating is for example at 125 vdc. So if the voltage is only 12 vdc, the current rating increases, correct? Or is the current rating fixed regardless of the voltage applied to the rheostat? This is why I was using watts as a guide. Thanks, Rob Rob,
That would not be my guess. The current rating is derived from the size of the wire used in the windings. The voltage rating would be derived from the turn-to-turn spacing, the breakdown voltage of the material used in support of the windings, terminal spacing, etc. The power rating would be derived from the ability of the package to dissipate heat. You could have a really skinny winding wire in a high voltage/low current rheostat with the same power rating as a thicker wire in a low voltage/high current rheostat. The skinny wire would burn up with higher current even though the power dissipation is not exceeded. Make sense? Wilf Wow . . . . I just learned a lot there. Thanks Guys!
I like the idea of the 12ohm resistor in series. So I'm looking to buy the correct Rheostat. If I have this right, the numbers would have to be, (this is going from the Ohmite list) http://www.ohmite.com/catalog/pdf/rheos ... ewound.pdf Model U: 100ohm, 1000w, 3.16amp Or I could go with the: Model R: 125ohm, 500w, 2amp This would put a minimum current of .096amp to the parts to start. Wilf what would be the best solution for plating with my equipment (12v 1.5amp Wall charger. Or better question, I guess, what is the best starting current and max current that a plater would need to do most any parts large and small? This might help others building a system to define the best start current and end max currents needed. Thanks Adam Corts
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