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C U R R E N T C O M B I N A T O R |
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The combined spark this device produced was amazing. It made a sputtering, pulsing sound and was thick, hot, and a blue-green color. The tips of my spark gap (copper) melted a bit. |
spark generated by the combination of sinusoidal [ ac ] and diathermy currents |
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Dear Mr. Barvoets, I checked our Wappler catalogs, and they do not have this device; but we hardly have a complete set. In any case, it does not look like a complicated device. A sinusoidal current would be created at a fairly low frequency, either sixty cycles (if ordinary AC were used) or at a variable frequency (if a motor-driven rheostat were used). Diathermy current would be made with a high-frequency spark-gap oscillator, a descendant of the Tesla or Oudin coils. The two types of apparatus do not get along well; Tesla burned up a Colorado powerhouse generator when he accidentally combined them in his lab. However, both currents can be useful in medicine - separately and together. A sinusoidal current is good for exercising muscles with minimal complaints from the nerves. A diathermy current is good for soothing aches. Combining the currents would let you soothe and exercise at the same time. This machine is simply a device (it could be a transformer or a capacitor, but I'm betting on the transformer) that lets you combine the outputs of two very different current generators and apply the sum to your patient. We have quite a few combination machines in our collection that do that; I suspect yours is intended to take two independent machines and allow their combined use. Yours -- Ellen Kuhfeld, PhD Curator, The Bakken Peter, As I look at the diagrams and the object, it becomes a bit clearer what is happening. The diathermy machine is connected to the patient through a capacitor on each wire. The sinusoidal current is connected through inductors on each wire. This is classic. Capacitors pass high frequencies, but block low frequencies. Inductors pass low frequencies, but block high. That way each of these machines -- sinusoidal and diathermy -- can get at the patient; but they cannot get at each other. It's not quite what I was expecting, but it makes more sense than what I had suggested earlier. Ellen Coils, chokes, inductors -- they are synonyms. (There's a technical adjective or two implicit in each of these words, and "chokes" is probably the best word to use for the blocking function yours perform. Now that I know the circuit, what happened to your combiner is plain -- plain as the way the spark got fat and blue when you had both currents going in. The radio-frequency (diathermy) current had a high enough voltage to start a spark, but not enough energy to make it fat and blue. Once the spark was going, the line power had the energy to overload the coils through the spark. (That would really be a good way to power a Jacob's Ladder. If we make one here, I'll have to try adding some high-frequency high-voltage to the mix.) Ellen Peter, I think the arc (initiated by the RF and sustained by the AC) conducted electricity so well it acted as a short circuit. Putting 110VAC into a short circuit can cause all KINDS of trouble. Cheap surge suppressors are merely a varistor connected across the AC line. This will absorb energy from overvoltages and cut them down to size. But a varistor can only absorb a limited amount of energy over its lifetime, and a setup like this -- even with the high-pass and low-pass filters -- is putting stuff into the powerline that a varistor was never meant to handle. To safely use a device like this in a modern electrical environment, you would need a very old-fashioned surge suppressor: heavy, stout chokes and large, high-voltage capacitors in their classic configuration. These can handle lots of energy, but they are large and expensive and not needed in ordinary use. You are doing something extra-ordinary. Tesla Coil builders have special devices to keep the RF from their coils from flowing backwards into the powerline. You should use these to isolate your machinery from the powerline, because a spark-gap diathermy machine is nothing more nor less than a Tesla coil with strong training in manners so it can be used safely on humans. And one notable aspect of a Tesla coil is that it is very generous in spreading its energies everywhere in the vicinity. Oil immersion would be a good idea for two reasons. It would insulate the coils from high voltages, and it would act as a convective heat sink. They use transformer oil in power stations for both these reasons. Be sure you get something that will not burn easily. Ellen |
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 Comparison of sparks. Top shows just diathermy. Bottom shows combined sparks. |
 The guts after the wax/rosin was melted out |
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After the device failed probably as a result of using AC for the sinusoidal current [ too much current? ] I melted out the wax/rosin to expose the inner workings. Below I have prepared a couple of simple schematics of the device. |
 This drawing shows the windings of one of the two spools. The coil wiring diagram above shows that the coil is actually one continuous length of wire. I'm not sure why the two wires that are connected between the inside top and inside middle windings protrude out of the top of the coil except maybe to anchor the windings. The top of the spool is indicated in the drawing by the thin blue lines. The wires pass through holes drilled through the wooden spool. The number of windings is as follows- top to bottom: 161, 159, 164. |
 A diagram of the entire apparatus. |
 The top of the apparatus. |
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If anyone has any further information on this apparatus, please contact me. I would be interested in
information about this device and any information about similar 'current combinators' as well. Thanks. Peter Barvoets 2003 |
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