WooHoo!!! Built and now just waiting for the toroid.

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WooHoo!!! Built and now just waiting for the toroid.

Postby DJKOR » Sat Aug 17, 2013 4:52 am

I was away for work for the last week and arrived back last night... conveniently on the same day my kit was delivered. Being the impatient person I am, I proceeded to get to work immediately. Started with the interrupter last night and then started on the main unit itself this morning.

Biggest challenge I came across was finding materials to build a toroid so I could at least fire it up to make sure it doesn't immediately blow up :lol:

After a bit of research, I managed to locate some 50mm drain piping and decided to be creative with that. I could not locate any aluminium tape like that included in the kit though. All I could find was the stuff with a butyl layer on the back to aid adhesion for plumbing use. I decided to make do with that.

So far so good. It seems to work, but I didn't want to turn the power knob past 1/3. The last thing I want to do is blow the IGBT's. Mainly to save the hassle. I do have a spare set on the way though.

Only issue I have come across is the laser cut pieces that form the base. To sum it up, the front side (where the High Voltage sticker is) does not fit into the cutouts on the opposite side. This means that the board orientation can only go one way on the base. The end result of this is that the IEC connector can not be inserted into the cutout and secured well with screws. Not too fussed about this but it is an OCD thing for me.

I hope everything is functioning as it should and that it will produce the correct sparks when I have the proper toroid and drive it harder. I have a scope to test things and would be curious to see how out of tune everything is at the moment, but I lack a function generator, hahaha.

So now for some photos:

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And some video (though no massive sparks):

http://www.youtube.com/watch?v=ccJQuKjZhlI

http://www.youtube.com/watch?v=QDM221EuC3g

http://www.youtube.com/watch?v=YV0GsKBLxII
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My build thread: viewtopic.php?f=15&t=998 | 246kHz Primary / 267kHz Secondary
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Re: WooHoo!!! Built and now just waiting for the toroid.

Postby DJKOR » Tue Aug 20, 2013 7:14 am

For the purposes of tracking progress on this coil, I figured I will post my update. After reading some posts on the forum here about adding more varnish to the coil, I figured I would follow suit. Probably a wise idea while waiting for the toroid before I start pushing the power past the halfway point.

I was doing a bit of research on whether to coat it or not but from what I gathered, the varnish would be good to help protect the secondary in the event of flashover and surface tracking. I found a product that I ideally wanted to use which is Electrolube Polyurethane Coating (http://www.electrolube.com/docs/conformalmain.asp?id=83). I could not find any local stock of this however and could only find the Electrolube High Performance Acrylic (http://www.electrolube.com/docs/conformalmain.asp?id=77). The former has an extra 15kV/mm in dielectric strength so I figured that polyurethane would be the way to go. Since I couldn't get my hands on that one easily, I just when down to the local hardware store and got myself a decent oil based polyurethane varnish.

Lacking a lathe or equivalent, I had to be a little creative. Holding the drill at low speed gives enough power to spin it for a couple of hours while the varnish becomes tacky. Will probably give it another 2 layer over the next few days and see how I feel.

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Also, thanks to the MIDI file from Dez, last night I decided to give my coil another run. Pushed it just a tad higher than my previous runs (2nd song test was about 40%, this one was closer to 50%) and so far nothing has blown.

http://www.youtube.com/watch?v=HlWdGhh1CTU
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My build thread: viewtopic.php?f=15&t=998 | 246kHz Primary / 267kHz Secondary
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Re: WooHoo!!! Built and now just waiting for the toroid.

Postby DJKOR » Sun Aug 25, 2013 4:51 am

Once again just updating my thread for progress. After building a simple 555 based frequency generator for the purposes of testing, I learnt that my secondary was out of tune and was resonating at about 288kHz. I experimented with some more topload and managed to bring it down to 265kHz (viewtopic.php?f=24&t=990&start=40#p1618)

I had since revised my toroid and it appears my secondary is tuned at about 260kHz. I started getting some odd readings though with the CRO the following day so I have chosen to just leave things as they are until I get a proper function generator and scope.

A quick test today showed that I was getting about 18.5 inch sparks at 50% power however it didn't look like turning up the power would yield anything larger. I'm not game enough to push the power higher in Fixed mode to really test if that is the case, so I will live with it as is in the meantime.

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http://www.youtube.com/watch?v=1s9Y5AwiWgw

Sticking with a midi that I have tried and tested before at a reasonable higher power when out-of-tune (thankfully I didn't blow anything at that point), I decided to give it another go but pushing the power to about 60% (I did hear a slight increase in volume in this case compared to the fixed mode, but this is where I drew the line). Despite my coil not being entirely perfect in accordance with the plans, I think it is safe to say that I am quite satisfied with my oneTesla. I have gone from dreaming about one day making a Tesla Coil, to actually making one. If it weren't for the oneTesla project, I probably wouldn't have made any progress for many more years:

http://www.youtube.com/watch?v=7q_Rvpk4bvs
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My build thread: viewtopic.php?f=15&t=998 | 246kHz Primary / 267kHz Secondary
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Re: WooHoo!!! Built and now just waiting for the toroid.

Postby Heidi » Tue Aug 27, 2013 12:21 pm

Beautiful work, thanks for sharing!
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Re: WooHoo!!! Built and now just waiting for the toroid.

Postby Bayley » Tue Aug 27, 2013 5:29 pm

Can I ask what the dimensions of your second toroid are? There are a few folk who are experiencing similar issues, and adding some extra topload might be more reliable than removing a secondary turn.
(Sorry if you posted this already in the other thread, that one is a confusing mess right now, so I figured for the sake of organization it would be best to ask here).
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Re: WooHoo!!! Built and now just waiting for the toroid.

Postby stegu » Tue Aug 27, 2013 5:45 pm

that one is a confusing mess right now


Yeah, sorry about that. That thread kind of exploded, but we learned a lot from each other by posting there.
Feel free to start a new thread to focus more on the current problem and not confuse the matter with our previous speculations that turned out to be incorrect. We'll follow your lead, and try to keep the new thread less polluted.
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Re: WooHoo!!! Built and now just waiting for the toroid.

Postby DJKOR » Wed Aug 28, 2013 9:26 am

Bayley wrote:Can I ask what the dimensions of your second toroid are? There are a few folk who are experiencing similar issues, and adding some extra topload might be more reliable than removing a secondary turn.


Hi Bayley. My two toroids have the following dimensions (measured with my super precise methods :lol: ).

Lower: 8.11 inches x 2 inches (273mm x 50.8mm)
Upper: 10.75 inches x 2 inches (273mm x 50.8mm)

The inner construction was from 50mm flexible drain hose which worked out perfectly when combined with the aluminium tape. No scientific decision went into making the second toroid. I simply just made one that I though't would sit comfortably on the second.

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I made each toroid as a separate piece so both are a mirror image top and bottom as per the photos. The larger toroid was not secured to the lower one during any of my runs. It simply just sat on top of the other.

I when I measured resonance with my inaccurate frequency generator and scope, it seemed that the larger toroid on it's own had a difference in resonance of about 3-4kHz when compared with the two combined. With that in mind and knowing that it shouldn't blow up if I keep the power down, I did a test run with just the larger toroid only.

http://www.youtube.com/watch?v=OEY2IvlFaqk

It seems to run at about the same power and volume as the stacked combination however I noticed it is more prone to give off sparks on the "sharper" edges of the toroid compared to the stacked combination where it appears all of the energy goes to the metal rod. Also, in the stacked combination, the primary coil feels ever-so-slightly cooler to the touch compared to the large one on it's own.

Most I've run it to is about 65% but haven't risked pushing it higher. In all cases, I have not noticed any flashover or anything like that.
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My build thread: viewtopic.php?f=15&t=998 | 246kHz Primary / 267kHz Secondary
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Re: Strange things.

Postby DJKOR » Wed Sep 18, 2013 3:43 am

I was going to start a "debugging" thread like the others, but figured I will leave this thread as the one where I will track progress.

So I finally got my hands on a function generator (which I tested with a frequency meter and it is spot on) and a simple pocket oscilloscope. It isn't anything super accurate but I compared it's readings with a good Techtronics from one of the offices I was in and it seems to be reliable around the frequencies I require.

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So first things first, I checked my primary and secondary resonance in the current setup as seen in the previous posts. The readings I got were as follows:

Primary - 246kHz
Secondary - 270kHz

Now remember this was where it was functioning quite well in my opinion.

Next I removed my second (larger) toroid and went about winding a new primary to suit. I wanted the toroid to be of similar size to the proper one I should receive soon as this is what would look the cleanest. I wound 4 turns of 2.5mm^2 wire (this was the closest I could find to AWG14 and is just a little smaller than AWG13).

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I then proceeded to measure the resonance and got the following:

Primary - 320kHz
Secondary - 326kHz

I turned it on and noticed that the spark and noise at lowest power was definitely louder however I ramped the power up to 50% and noticed the spark was definitely nowhere near what I had before. I quickly shut it down to avoid catastrophe.

***** While typing this, I just had a "durrrrr" moment when I picked up my original primary. I realised I should have went for 5 turns. Don't know why I thought of doing 4. Oooops.

Stay tuned for further progress.
Last edited by DJKOR on Thu Sep 19, 2013 1:48 am, edited 3 times in total.
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My build thread: viewtopic.php?f=15&t=998 | 246kHz Primary / 267kHz Secondary
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Re: WooHoo!!! Built and now just waiting for the toroid.

Postby DJKOR » Wed Sep 18, 2013 6:10 am

Okay, so after my bit of a blonde moment, I went and wound 5 turns of the primary.

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Remeasured my primary resonance and got 293kHz. So that now brings the Primary/Secondary resonance to 293kHz/320kHz. My scope has limited resolution on the output image but I have attached a trace (at 10us) when the coil was running about 1/3 power. I could do some measurements on the scope but due to work, I can only run this thing at night and it is quite noisy, so that will have to come later.

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I am getting quite a bit of breakout from various edges of my DIY toroid which isn't helping towards getting big sparks so I'm not too sure whether things are actually better than before or not.

Quick calculations indicate that my original configuration was 9.7% out of tune whereas my new configuration is 9.2% out of tune. One would think that both configurations are performing about the same then and if the !0% difference in tune is anything to go by, then I would imagine that my coil is currently set correctly.

I have to wonder though, why would I be getting more breakout from other points on the toroid compared to my previous configuration where all the power seemed to have been sent straight to the rod?

I then adjusted the breakout point to be a couple of inches further out. Remeasured secondary resonance to then be 316kHz. That then brings the difference in resonance to 7.5%. I did recall hearing that for a smaller coil to maybe aim for 5% so I thought a lower number might be better. Ran the coil and noticed that most of the spark was now breaking out from the breakout point itself. I'm not sure if this is due to a difference in tuning or the fact that the breakout point was further from the main mass of the toroid. I don't know enough about all this.

One thing observed though is that even though the spark at minimum power appears to be much larger than it was in my previous 2-toroid configuration, the spark at 50% power appears to be shorter. Could this be due to the higher frequency of the tuning maybe? Less capacitance of the toroid? Both? These are all questions that I guess I will find through trial and error. If it is due to the higher frequency only, then maybe I would be better off sticking with the 6 turn primary and obtaining a secondary with more windings so that the combination of 8x2 inch toroid plus secondary would result in an in-tune coil. So may variables.

http://www.youtube.com/watch?v=PHHkPLm6AJ8
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My build thread: viewtopic.php?f=15&t=998 | 246kHz Primary / 267kHz Secondary
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Re: WooHoo!!! Built and now just waiting for the toroid.

Postby stegu » Wed Sep 18, 2013 9:46 am

There are many variables to consider when you tune a coil, yes. However, your scope trace looks really nice, with a quite steady ramping up of the power during the entire pulse from the interrupter, and a smooth and fairly slow decay after the pulse. My traces so far show considerably more "bucking" in the ring-up part (uneven transfer of energy back and forth between the primary and secondary) as a result of interference between the primary and secondary resonant frequencies.

Like you observed, it is impossible to get a good spark at minimum power while also having a good spark at higher power, and if you hit perfect tuning at a certain spark length (say, at half power), it is difficult to get it to grow much further without retuning the coil. I'm at that point right now: I have very good performance at 50% power, but I don't get significantly longer sparks on 100% power. More power gives me thicker and hotter sparks, but not longer. I will retune by tweaking my primary in small steps when I find the time, but what's left are very slight adjustments that also depend on the environment, mostly the distance to and conductive properties of nearby objects, but also to some extent humidity, temperature, perhaps even the phase of the moon. (No, not really the phase of the moon.)

To get the really long sparks, you need to tune the primary and secondary frequencies to match very precisely. To make the secondary continue to be pumped by the secondary after a spark breaks out, you need to hit a small sweet spot and make the detuning without a spark just right, to bring the entire system precisely into tune for the long spark you want.

10% detuning at zero power (low voltage measurements of the resonant frequencies) seems to be a reasonable ballpark figure. If anyone with really strong and impressive sparks at full power could post measurements of their primary and secondary resonant frequencies using a signal generator and an oscilloscope, it would be much appreciated and provide much more specific advice for the rest of us who are still struggling to see those 20" streamers.
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