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Steve Conner

Sun Aug 22 2010, 10:19AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Hi guys

Haven't been on the forum for ages, I've been busy with lots of things! Anyway, this is one of them: a mini DRSSTC contained in its own portable Faraday cage. My work commissioned me to build it for the UK Innovation show in Shanghai. It's already on its way out there, and I'll soon be heading out too to play electric guitar through it.

The primary and secondary formers are made of plexiglass, mostly laser-cut. (No blue LEDs. :P) The secondary is wound with 0.125mm wire for a resonant frequency of about 260 kHz.

The electronics are a straight copy of Mjollnir, only with a half bridge instead of a full one, and improved EMI filtering.

The Faraday cage is a 19" rack flight case fortified with wire mesh. (The back was removed for the photo.)

I don't have any spark pics, because I had to tear the thing down and send it off literally as soon as it was completed. The only design objective was to hit the walls of the cage, and it manages that easily.

aonomus

Sun Aug 22 2010, 07:22PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Great to see that you went through with it Connor! I hope this time the Chinese gov't don't confiscate it like what happened to kVA effects....

GeordieBoy

Mon Aug 23 2010, 03:30PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

Very nice!!! Is there mesh across the front of the box too, or is this open to the air for maximum visibility of the sparks?

Have fun demoing it in Shanghai !

-Richie,

Dr. H.

Mon Aug 23 2010, 07:52PM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Beautiful work Steve. Love the "tiny" meters

P.S. And why you didn't put blue LEDs hee hee

Cheers

lpfthings

Thu Aug 26 2010, 05:50AM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

Too be honest, blue LED's would take away from the sparks on such a small coil. I've found that with my tesla coil, a brief look at the blue LED's makes it hard to look at the arcs properly.

Thats once nicely built coil though, and audio modulation too!

Dr. H.

Fri Aug 27 2010, 05:41PM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

That's why I put a switch on my blue LEDs

Cheers

Steve Conner

Sat Aug 28 2010, 10:30AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Hi all

Well, if the Chinese government are going to confiscate it, they'll have it by now.

I'm heading out on Wednesday.

Richie: The last shot is the back, and normally everything except the mains inlet is covered by a big panel of wire mesh. For shipping, I dismantled the primary and secondary, packed them in a cardboard box with lots of bubble wrap, which I then stuffed back inside the cage and replaced the back.

Due to running out of time, I had to ship it without the audio modulation. I just got that finished yesterday.

Dalus

Sun Aug 29 2010, 10:35AM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

Can't wait to hear those ''cutting a gameboy in two like' guitar sounds from the coil. Hopefully with a nice display of arcs

It's nice to have such a small safe compact demo coil.

Steve Conner

Thu Nov 25 2010, 08:18PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Update on this project:
The coil arrived back from China this week, and on unpacking, it was found to be still working fine!

So, here are some more pics and a closing report.

The secondary was wound using a drill press hooked up to an audio amp cranking out sine and cosine waves at a few Hz. This ghetto variable speed drive made it rotate very slowly. Winding the 0.125mm wire was still very fiddly, but worth it: the dinky coil resonates at a manageable 220 kHz.

Finally a spark pic! :) Two breakout points produce bunches of sparks at the right angle for good viewing. The cage is easily filled with hot, noisy arcs that climb the walls like a Jacob's Ladder. Hot air reeking of ozone rises out of the top. I guess you are all wondering, "How far would it spark if it was taken out of the cage?" Well, we can't really do that in the R&D lab at work, in case it hits the 3GHz LeCroy.

One of the Chinese student volunteers demonstrating the coil. "Lewis" - sorry can't remember your Chinese name :( - is studying railway engineering at Shanghai Metro University.

This shop sold a whole lot of stuff including the blank DVDs I needed, for 4 yuan. Maybe that was the foreigner price, but I didn't bother to haggle.

Surrounded by Dutch tourists in Yu Gardens.

In closing: I'm still totally stoked that I was paid to build a Tesla coil and travel to China with it. I'm delighted that it didn't break down and I got it back afterwards. And I learnt a lesson, that size and power isn't everything. My next coil was supposed to be a brick-powered monster, but my boss approached me and asked if I could build a smaller one. This is actually the smallest I've built.

The porta-coil will strike again soon! :)

vasil

Thu Nov 25 2010, 10:21PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Thats really a cool coil.
...thinking to get back to drsstcs....

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