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first allow me to introduce my self. im tony. im a computer tech by day, and by night, well i sleep lol. anyway, ive always tinkered with electronics and i have built a few high voltage supplies in the past. just simple multipliers and such. ive had an itch to build a tesla coil for some time, but now im finally going to try it. so naturally i have a few questions.
i wound a secondary last night out of boredom on an 8" piece of pvc pipe i had sitting here. it's od is about 3/4". used 30awg enameled wire. got about 730 turns based on coil length and wire thickness. it was mostly a practice coil but it came out really well so if i can use it then i will. i worked out the math for the resonant frequency of the coil and the topload i have in mind, and it needs to run at roughly 1.7MHz. this seems a bit high to me. so heres my first question, is it even possible to reach frequencies that high with a spark gap? a solid state circuit might be better for a small scale coil like this but i was hoping for a very low cost and simple setup. 4 or 5" sparks from this thing would make me a happy camper lol. oh, i should also mention that to run it i plan to use a small nst. 9kv 30ma. any thoughts?
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
1.7GHz is not an achievable resonant frequency with a 'normal' Tesla coil. It is probably 1.7MHz. The spark gap works at any frequency, as it does not turn on and off at 1.7MHz, once it breaks down it stays on, like a wire shorting it, and the 1.7MHz will be between the inductor (primary) and capacitor (the tank cap).
sorry, MHz is correct. thats what i get for making a quick post while distracted. ill edit it. i think im having a hard time visualizing the operation and energy flow in my head. so the sg sits in parallel to the nst, and the tank cap sits after the sg in series with the primary which then connects back to the other side of the sg, correct? the way i was picturing it was the hv supply would charge the cap to the point that the sg would break down, completing the circuit discharging the cap tank into the primary, resetting the sg. this makes sense in a DC scenario, but not so much for ac, and now that youve said the sg doesnt control the timing, i feel a little lost. i dont have a lot of experience with spark gaps so if you could better explain whats going on with the energy flow in the supply circuitry id be much appreciative. thanks by the way for the quick response :)
EDIT: ok i've got it figured out. this site explained it very well. http://hvtesla.com/
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
ttt -
Before you get off on a tangent, you need to gain some good technical insight into what a Tesla coil is, how it works, the function of every component, how resonance is achieved, circuit topology, spark gap quenching, ringup, etc.
Still the world's best source for this information is Richie Byrnett's website at:
There is literally months worth of reading here, but focus first on the sections covering conventional AC spark-gap coils. This will provide the foundation you need to properly design and tune a coil, and get it running with minimal complication.
A question: what factors led you to select a resonant frequency of 1.7MHz? Do you know what value tank capacitor would be required to resonate with your sub-miniature secondary, and what the "bang energy" would be each time the spark gap fired?
If your objective is production of spectacular sparks, then a coil powered by a 9/30 NST and operating at 1.7MHz is not the way to go. A properly designed spark-gap coil powered by a 9/30 NST with a secondary 3.5" diameter with a resonant frequency of 300-450 KHz will provide much more satisfactory visual performance.
Before you get off on a tangent, you need to gain some good technical insight into what a Tesla coil is, how it works, the function of every component, how resonance is achieved, circuit topology, spark gap quenching, ringup, etc.
Still the world's best source for this information is Richie Byrnett's website at:
There is literally months worth of reading here, but focus first on the sections covering conventional AC spark-gap coils. This will provide the foundation you need to properly design and tune a coil, and get it running with minimal complication.
A question: what factors led you to select a resonant frequency of 1.7MHz? Do you know what value tank capacitor would be required to resonate with your sub-miniature secondary, and what the "bang energy" would be each time the spark gap fired?
If your objective is production of spectacular sparks, then a coil powered by a 9/30 NST and operating at 1.7MHz is not the way to go. A properly designed spark-gap coil powered by a 9/30 NST with a secondary 3.5" diameter with a resonant frequency of 300-450 KHz will provide much more satisfactory visual performance.
Rergards, Herr Zapp
like i said in my first post, i just wound that coil for practice. i was really bored. my car is out of service at the moment so ive been stuck home all weekend. and i live alone. yucky. the coil came out really nicely so i figured why not see if i could build a tiny coil out of it. then i worked out its characteristics and tried to see if i could make one out of the junk ive got laying around. i know this is a backwards way of doing things, but after 2+ hours of winding i grew a little attached to it haha. i may not try to use it at all. im half thinking about throwing a little money at it and making a well designed, and much more fun one. i just enjoy putting things together out of whats in front of me. im really good at putting things together in my head then building what i see. was more going for "look what i pulled out of my rear" vs "look at the light show"
checked out that website. wow! very nice. more than i ever wanted to know haha, but i promise ill read and understand every page before i start on a big one. i've done quite a bit of reading already over the years, enough to be able to make one that at the very least works. i just really like to be able to picture its complete operation in my mind in slow motion before i start. anyone can follow some well drawn schematics, but to fully understand what exactly is going on is a whole 'nother story. :)
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