Instructables

how to build a table top VTTC (vacuum tube tesla coil)

i want to know how to build a table top VTTC (vacuum tube tesla coil) i found only one instructable on it from Xellers,
How To Build A Vacuum Tube Tesla Coil (VTTC)


1) what type of vacuum tube should i use? what is the most powerful, yet in-price-range tube i can get (no more than $50)?

2) what are the values of all the components in the schematic below? (T1, C1, C2, VT, R1, L1, L2, L3)

3) how much will it cost? [answered]

4) is the output dangerous for a table top version of it? (answered)

5) lastly, is it possible to modulate so its more like a "singing ark" and\ or transmit AM?

6) will the last schematic work?

7) do i need i M.O.T transformer or high voltage power supply?


Picture of how to build a table top VTTC (vacuum tube tesla coil)
VTTC.gif
VTTC revised.gif
Xellers4 years ago
You can follow the link in step 4 to the complete schematic. The parts are listed in the schematic, as well as in step 5. A cost estimate is also given in step 5. In order to modulate the coil, you need steady DC power supply; in this particular schematic, the oscillator is only active during the positive half cycles of the current provided by the MOT. This means that you are already modulating a 60Hz signal into the coil, and this is reflected by the loud buzzing noise it makes when it is turned on. To modulate audio, you would need a full wave rectifier and a filter capacitor in the power supply (I can already see a half wave rectifier in your second schematic, but this will still cause some hum, use a full wave rectifier). However, if you continued to use the MOT in this configuration, it would destroy the tube almost immediately - you would need to significantly reduce the power supply voltage, which would in turn reduce the spark size. Also, this would add about $50 to the cost of the project because MOTs are relatively easy to come by and you can find one for next to nothing (if you can't find one for free inside of a broken microwave oven), while other high voltage plate transformers are rare nowadays and would probably have to come out of vintage radio gear. (I have also posted this comment an answer to your comment on my instructable)
Xellers Xellers4 years ago
As an answer to part 4 of your question, the output of this coil is not very dangerous in that it will not kill you, but it can cause painful RF burns if you come into contact with it for more than a second or two. I would deem this safe enough for a tabletop coil, but the MOT is what you really should be worried about; it will kill you if you come into contact with the primary side of the circuit. The best way to make this coil more safe would be to enclose the primary electronics in some sort of chassis and mount the tube on the top. Of course, this will still pose some risk (if you touch the primary coil, for instance), but it will be relatively safe if you stay away from that area.
-max- (author)  Xellers4 years ago
thanks, ill wait for some other answers before i mark you best answer.OK, can i use a LOW voltage transformer (like a wall wart) instead of a deadly 2000 volt MOT? or better yet, a few car batteries and a voltage regulator? and more winding on the primary for more power on the actual tesla coil?
Xellers -max-4 years ago
No, you cannot use a low voltage source to power your Tesla Coil. The tube needs a certain voltage on its plate in order to operate and it needs even more voltage in order to be able to operate at the power levels this coil demands. You might be able to get away with building a small coil using a source of several hundred volts instead of a few thousand volts, but the results would be unimpressive. Also, your alternate schematic (posted on my instructable) will not work. You need the other components in order for the oscillator to work properly, they are not optional. Additionally, your other schematic looked like some sort of Hartley oscillator remix, the schematic in my instructable is of an Armstrong oscillator, and you will need different parts in order to build a Hartley oscillator. Also, the number of turns on the primary coil has little to do with the energy transferred into the secondary coil. Here, resonance plays a much more important role than brute force. Try reading about RLC circuits and the "Q factor" to learn more!
-max- (author)  Xellers4 years ago
also, how did you manage to touch the output without burning yourself, the ark looks SUPER hot!!!
-max- (author)  Xellers4 years ago
i don't want the full schematic as it cost more for all the parts if the simple version is operational