Paul: After yesterday’s pie-in-the-sky engineering I got to thinking about how many amps might really be required. 120V or 12,000V doesn’t mean much unless the amperage is high. Nobody ever got electrocuted from a spark plug, and those are tens of thousands of volts. My thought was that a ballast already limits current, so why not use it, regardless of the voltage? Today I looked up the rated ampacity of 0.050 wire (about the size of a center pin) and it is around 6 amps! To heat the pin quickly it would probably take 15 to 20 amps. Yes, a low voltage is necessary. The ballast idea is unworkable. But then I got to thinking about the skin effect of RF current. Wouldn't it work better if only the outside surface of the pin were heated. So what if the procedure could only be done inside of a farady cage so as not to mess up everybodies cell phone? Minor inconvienience! On Mon, Mar 30, 2009 at 3:45 PM, Paul McCloud <pmc033 at earthlink.net> wrote: > Hi, Jeff: > I'm still a little confused about the ballast idea. You want to put > 120 volts into the probe? Ahh, well, I'm not sure about that. > The first thing is, the transformer (I assume we would use one to > drop down to a safe voltage) has to have sufficient over-capacity to not > overheat. Then, the current should be steady, though it doesn't have to > have extreme precision. And, the duration of energy has to have control. > I've seen timing modules that plug into a socket, with built-in > timing capability, and some with timing control. There are some with output > terminals that could be connected to a second circuit (continuity > verifying), though I couldn't figure out how to make the switching > automated. The idea was to energize the circuit with the probe, then the > timer would send the power pulse, then de-energize the circuit after > removing the probe, thus resetting. > With a large current input, you would only need about a second or > so. It would be nice to be able to monitor the temperature of the pin, but > that would be difficult to do. > How about this idea. You could charge up a capacitor and let it > discharge into the circuit. If there's enough energy to do the job, you > wouldn't need a current source, limiting circuit or all that other stuff. > You simply discharge it into the flange pin. Would there be enough energy > to heat the pin? I'd have to do some figuring. There would be no worries > about heat, and if you needed more power, you'd just connect up another > capacitor. Hmmm (at about 60hz). > Years ago, my father was a Ham, and he sort of got me interested. I > got my license back in the early '80's. I understand you don't need any > Morse Code to get a license nowadays. Sort of like, not having to learn to > tune aurally if you have an ETD. There are code readers that translate the > code and have a keyboard so it will encode it before you transmit. Why do > you need to know Morse Code? I haven't been on the air for about a decade. > It's an interesting project. I think your tuning study is probably > more important at this point, though. And certainly more to your bottom > line. > More later, > Paul -- Regards, Jeff Deutschle Please address replies to the List. Do not E-mail me privately. Thank You.
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