Metallica-Paranoid on the OneTesla

[jeffcrilly]

Short video of the OneTesla playing "Paranoid" tonight...

https://www.youtube.com/watch?v=L_QOLx-6eXg
There's some pretty big arcs there.
((Edit: Fixed.. is now not private!))

(This is in HD, btw.. 1080p)

Earlier: Popcorn...
https://www.youtube.com/watch?v=635XW2JfYKI

[Artlav]

This video is private.
Sorry about that.

Paranoia indeed.

[Heidi]

Nice build! Thanks for sharing.

[jeffcrilly]

Nice build! Thanks for sharing.

Nice Kit!

I've been looking for something like the OneTesla kit since I read this issue of Popular Electronics: http://home.gwi.net/~jdebell/pe/6407_cov.htm
(Note the tiny tesla coil on the left. The blue box.)

Btw, on first spark i had poor performance. After blowing and replacing IGBTs (thx for supplying spares), i still had poor performance. I decided to replace the primary as there was arcing from the primary where the wires start winding. (I think I twisted the wires too tight.) The new primary is 6 turns 12AWG (instead of 14AWG). I also left the clips off and used electric tape.

Performance seems way better. But I believe I still need to measure the resonance. I did measure resonance using an oscilloscope 10 feet from the OneTesla and got this : http://youtu.be/VxivzK79xo8 (forward to the 45 second mark)
I counted the graph for the two parts and they seem slightly different.

[stegu]

Your secondary has about 15% higher resonance frequency than the primary. Not a lot, but enough to reduce the efficiency and yield a weak spark, and also enough to cause catastrophic breakdowns at high power by blowing the IGBTs. I can't tell the exact numbers from your video, because the image quality is not great, and the time scale is unknown, but guessing that you had 10 us/div, the primary seems to be about right even after your rewinding, pretty close to 250 kHz resonance, but your secondary frequency is higher, about 280-290 kHz. This is similar to what a few other people, myself included, have reported. Have a look in the forum section "Performance problems". I started a thread there about my rather serious detuning issues, and it has collected comments and discussions from several other coilers. The reason for the problem is still unknown, but we're working on it together, and Bayley from oneTesla is helping out.

(If you didn't have 10 us/div on the scope, it may be the case that your rewinding of the primary resulted in a tighter winding (despite your thicker wire) which increased its inductance and brought the primary frequency down. In that case, your secondary may be right, or at least closer to the correct value, and your modified primary may be part of the detuning issue. The inductance of a coil is quite strongly dependent on its length, not only on the number of turns.)

Your arcing issues can probably be eliminated by applying more PU coating on the secondary.

[jeffcrilly]

(If you didn't have 10 us/div on the scope, it may be the case that your rewinding of the primary resulted in a tighter winding (despite your thicker wire) which increased its inductance and brought the primary frequency down. In that case, your secondary may be right, or at least closer to the correct value, and your modified primary may be part of the detuning issue. The inductance of a coil is quite strongly dependent on its length, not only on the number of turns.)

Your arcing issues can probably be eliminated by applying more PU coating on the secondary.

Thx for the reply on the perf issue. I've been following the other thread.. However some of my posts weren't making it through... Needed moderator approval but Heidi might have since fixed that.

I am pretty sure (99%) the scope was on 20us. Yes the video was nearly useless, and seemed to have a lot of anomolies. I also counted the output (given the lousy video) and it seemed to have differing counts for the primary and secondary parts of the waveform.

The original primary had a real tight twist in the wire right before the windings, and even a kink I put in it with pliers when I was trying to get the wire tight, also there was a spot or two with a gap between windings. I also tested the old primary and two additional coats of polyurethane on the secondary; no change - still arcing. The arcing seemed to be originating from the "tight twists" I mentioned.

With the new primary (12awg was all I could find) I wound it as tight as I could, taped it to keep the windings together (clips would not fit anyhow), and kept the leads smooth, no excessive twists, no kinks. Btw, the oscilloscope video is with the new primary. I still want to get the tuning verified even tho it ~seems~ to be performing. We ran it for a fair amount of time at mostly high power... no blown IGBTs. Right now the testing blocker is "noise".. I need to pick a time so I won't irritate the neighbors (or figure out how to run the coil in the house.. It's kind of a small house B^).

Re the primary length: I definitely need to understand inductors a bit more.

It also cannot play some midi songs. E.g pirates-of-the-Caribbean, bumblebee.. Not sure why. Might be related to the midi player on the Mac (iirc it is midiwind), so I will give a windows player a try. Hopefully not a logic circuit issue.

[stegu]

The arcing seemed to be originating from the "tight twists" I mentioned.

That explains it. Tight corners are like a honeypot for arcs to form.

If you really had the scope at 20 us/div at 0:45 in the video, check its calibration. Most scopes have a variable control for the time scale, with the nominal timing referring to what you get at one end, and then a variable range of about 2x to the other end. The image at 0:45 is definitely shot with around 10 us/div - you have between 2 and 3 wave peaks per square on the scope screen. If you had 20 us, your resonance frequency would be only 120 kHz, and that is highly unlikely.

[jeffcrilly]

I see. I will doublecheck this. Thx.

[DJKOR]

It also cannot play some midi songs. E.g pirates-of-the-Caribbean, bumblebee.. Not sure why. Might be related to the midi player on the Mac (iirc it is midiwind), so I will give a windows player a try. Hopefully not a logic circuit issue.

FYI, I have tried Sweet MIDI Player and QMidi and all it kept doing was playing back one note every couple of seconds despite the LED on the USB to MIDI adapter flashing rapidly. Funnily enough, those were the only two songs I tried.

I didn't bother anymore after that as I didn't want to risk breaking something (paranoia in me after taking care building the kit), so I just fired up Parallels and used MidiEditor.

[stegu]

You need to make sure that all notes you want to sound from the coil are in channel 0. This is typically not the case for a regular MIDI file with more than a single instrument track in it, and it might not even be the case for monophonic MIDI files. General MIDI has default instruments for the channels, with "Grand Piano" being the default for channel 0, and some files use the defaults and pick a different channel instead of changing which instrument maps to channel 0.
The "MIDI Out" light on the MIDI adapter will flash for any MIDI message, but all except the ones concerning channel 0 will be ignored by the oneTesla interrupter. Nothing bad will happen to your coil or to your interrupter if you try a random MIDI file, but don't expect it to work right, or even work at all, unless someone made it specifically for the oneTesla.