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I just completed a new DRSSTC which went together surprisingly quickly, starting in late December and making big sparks by end Feb 2014. I've also created a detailed write-up on how I built the coil and other bits of information which will hopefully be useful for future coilers. I originally built this coil at home but it turned out to be a bit too large - turns out that the local Science Centre has a Tesla Coil exhibit, so it's now the new home for the coil.
As you can see it's not a very large coil (Especially compared to the bigger conventional spark gap one beside!) with a 6" by 27.5" secondary. The coil originally ran on a full bridge of CM200 IGBTs but has been recently upgraded to CM300 IGBTs for robustness. At 700Apk (not running it at 1500A like the other guys for more reliability ) it does about 7 feet of spark. Not bad for a 27.5" long secondary I think. We've decided to run it at 180VAC in instead of 240VAC which our power source can supply (we have a 60A 240V line) again for reliability. The blue tool box was there because the ground strikes were getting a little bit too close to the box!
- CM300DU-24NFH, 700Apk limited - 4700uF 450VDC Bus Capacitor x 2 in voltage doubler configuration - 375nF 10kV MMC 150A rms - Modified UD2 driver - Flat Spiral Primary, 1/4" Copper Tubing, - 27.5 x 6.3" Secondary, 79kHz - 6" x 28.5" + 12.6" x 2" Toroids - Designed for 240VAC input max for 678VDC
The guts of the coil with an improved laminated bus. I'm happy with how that turned out. The coil has been working very well! See my webpage above for more photos and videos.
And finally a video of it playing Pirates of the Carribbean at about 5 RF cycles per pulse. After a say 2 minute run at about 5kVA average input from playing music, the IGBT heatsink gets just lukewarm to the touch. The primary cabling and primary coil however does get noticeably warmer. Everything else runs great and the MMCs should be indestructible for this coil. : )
Registered Member #30656
Joined: Tue Jul 30 2013, 02:40AM
Location: UK
Posts: 208
Great looking coil, and excellent write-up and photos! When I was building my coil I was inspired by some of your earlier photography, good to see your photos of something bigger.
As for the coil, it's almost identical to the one I built in terms of both specifications and results (reassuring to see I did it right!) Mine has been running since late last year on 200A IGBTs and a 700-750A OCD with great reliability, though probably with shorter on-time than yours will see in the museum. If I try to push the spark length beyond the ~2.1m (7ft) mark (my current best) I'll let you know how it goes - I've had no issues at that length apart from an occasional strike rail hit so hopefully there is another ~0.5m still to be had. I have the ability to easily adjust the coupling and primary capacitance so I've got a few more tweaking options than you to get there, but I suspect it's just a case of more current and good tuning.
A final quick question, I was interested in the waveforms showing different gate resistances, can you tell us what the resistances were for the different scope shots? It's something I should probably investigate on my coil, I've just been reluctant to do so due to the effort of changing the resistors.
Registered Member #2694
Joined: Mon Feb 22 2010, 11:52PM
Location: Russia, Volgograd (Stalingrad).
Posts: 97
Mads Barnkob wrote ...
Intra wrote ...
Kizmo wrote ...
Nice coil and very nice photography you got there!
What's your secret?
I think, his secret is Canon EOS 5D Mark II & EF70-300mm f/4-5.6 IS USM.
I can tell you that equipment alone does not give good pictures, I have a EOS 5D Mark III ;)
Hmm... maybe. But, did you turn on your camera ISO and Shutter on maximum and Aperture on minimum when you try to get a shot? Also, of course, this photo has gone through the Photoshop. You're right.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Intra wrote ...
Mads Barnkob wrote ...
Intra wrote ...
Kizmo wrote ...
Nice coil and very nice photography you got there!
What's your secret?
I think, his secret is Canon EOS 5D Mark II & EF70-300mm f/4-5.6 IS USM.
I can tell you that equipment alone does not give good pictures, I have a EOS 5D Mark III ;)
Hmm... maybe. But, did you turn on your camera ISO and Shutter on maximum and Aperture on minimum when you try to get a shot? Also, of course, this photo has gone through the Photoshop. You're right.
These pictures are clearly made with a good even back light, lots of blue colours in the room already, ISO does not seem to be so high as noise it not prominent at all, shutter speed could be around 5 to 10 seconds from looking at the movie, depends entirely on the BPS of the Tesla coil. Aperture is for sure not at minimum, you have a deep field of depth in focus here. Colour correction, white balance etc done afterwards.
Just a guess :)
Also a nice Tesla coil and cool to see amateur work being used at the science centers!
Hey everyone. Have been busy away from 4hv for a few weeks and didn't see all the comments! Thanks for the kind words everyone. This coil wouldn't have gone together so easily without the previous help and advice from people in this forum in my many previous projects.
As for the photographs, I actually took a bunch of these with the Sony RX100 because my SLR does get a little big to carry around, and I didn't have a tripod so I had to balance it on things like railings and other objects. No secrets here, but here are some things I try to do:
1. Get the background lighting right. It depends on what sort of sparks you want. Bright sparks but few of them, or many thin-looking sparks? For the science centre coil, I had to talk to the people to turn off the main lights from the other exhibits but it was still a bit too bright for my liking.
2. Expose for the background first. I usually try to slightly underexpose. Tesla Coils like being photographed in manual where I get to adjust everything to suit my liking. I try to get the exposure to be between 1 and 5 seconds. This really depends on the frequency of your coil though.
3. For brighter sparks, you'd want a bigger aperture and higher ISO. The shutter speed depends on the brightness of the place as determined in step 2. This will affect the brightness of your sparks. It helps when my DRSSTC 3 makes very bight sparks, much more so than my other coils. F1.8 on the RX100 helps a lot. Then I adjust the frequency to get the spark 'density' I want in the photo. My interrupter has a momentary switch so I can very carefully fine tune how much spark output I get per photo.
4. I usually tweak the white balance in the computer later, or set it to daylight (usually daylight gives nice results). This actually depends more on the background lighting.
Finally, I do also use a Canon DSLR (I've used cameras ranging from a 350D to a 5D) when I feel like carrying it around, but all reasonably good cameras are really the same. As a photographer also, the camera is tool, and they're all very good these days not like several years ago! Finally, good to have a f2.8 lens or brighter for fatter looking sparks.
For those interested in more photography, you guys can check out my flickr here: . It has more photos of my coils and, I hope, much more new things to come
Interrupter Order: I recently needed to make a few new interrupters (same as the one this coil is using) for my own, and thought that maybe some coilers would be interested. It'll save both of us money in bulk order and PCB fabrication. If you're interested to get an interrupter, check out the thread here:
Another video of the coil playing tunes:
I'm happy to report that the coil is still running well in the Science Centre after three months or so.
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New CM200/300 DRSSTC
) it does about 7 feet of spark. Not bad for a 27.5" long secondary I think. We've decided to run it at 180VAC in instead of 240VAC which our power source can supply (we have a 60A 240V line) again for reliability. The blue tool box was there because the ground strikes were getting a little bit too close to the box!
