DigiTan
New Member
Okay I've got a few power source and temperature questions regarding a project I'm working on for this winter. Basically, I want to build an immersion heater to heat up a small etch tank (250ml-750ml) for my PCBs. Keeping with electrical safety, I wanted to ask you guys a few questions before I got started.
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(1) My first question is about the power transformer I'm using to step the mains voltage down from 120VRMS to 6 Volts. The transformer has the rating "4.5A" imprinted on the secondary. Is this 4.5A the absolute max rating? And is this RMS current? Also, with the center tap at ground and the two secondaries at 6 Volts, is the max power 4.5A*6V or 4.5A*12V? And if the secondary rating is 4.5Amps, what fuse do you recommend for the primary?
(2) Next, I'm trying to calculate how much power the heater needs to dissipate to heat the Ferric Chloride in a reasonable amount of time. Before I can do this, I need to know what temperature the FeCl3 needs to be. MG Chemicals suggested heating it to no greater than 130°F (55°C), and I was thinking 110°F (43°C) to 120°F (49°C) sounded about right. Is that pretty reasonable?
(3) Also, I'm trying to Google for the specific heat of Ferric Chloride, but so far I'm not getting much. I need to factor this in for the heater design, so any information would be helpful. If it helps, the MSDS is here.
(4) Finally, I have a question on possible heating elements. I was thinking of using several power resistors in a parallel or series fashion--isolated from the FeCl3 by Pyrex glass. Can anyone recommend any good threads, or web articles on using resistors as heaters?
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(1) My first question is about the power transformer I'm using to step the mains voltage down from 120VRMS to 6 Volts. The transformer has the rating "4.5A" imprinted on the secondary. Is this 4.5A the absolute max rating? And is this RMS current? Also, with the center tap at ground and the two secondaries at 6 Volts, is the max power 4.5A*6V or 4.5A*12V? And if the secondary rating is 4.5Amps, what fuse do you recommend for the primary?
(2) Next, I'm trying to calculate how much power the heater needs to dissipate to heat the Ferric Chloride in a reasonable amount of time. Before I can do this, I need to know what temperature the FeCl3 needs to be. MG Chemicals suggested heating it to no greater than 130°F (55°C), and I was thinking 110°F (43°C) to 120°F (49°C) sounded about right. Is that pretty reasonable?
(3) Also, I'm trying to Google for the specific heat of Ferric Chloride, but so far I'm not getting much. I need to factor this in for the heater design, so any information would be helpful. If it helps, the MSDS is here.
(4) Finally, I have a question on possible heating elements. I was thinking of using several power resistors in a parallel or series fashion--isolated from the FeCl3 by Pyrex glass. Can anyone recommend any good threads, or web articles on using resistors as heaters?