Tesla Coil Beginner's Guide

Originally from an email to a friend.
What follows is Tesla Coil construction advice from a rank amateur, with no warranty as to correctness or suitability for any purpose whatsoever - ok, my lawyer's not looking over my shoulder anymore.

First, what do you have available? Tesla coils need a hv source, capacitor, two coils and a top load.

HV source - old neon sign transformers are a good starting point. You will need one without a GFCI, as this safety feature makes them useless for a TC. Check sign repair shops for old throwaways. Another good source is the transformers out of old microwave ovens - these can be had free if you watch for them in the trash. They will likely require either a matched set (difficult to find, even in identical microwaves), or a voltage doubler circuit. I have a few, condition unknown. Automotive ignition coils are also possible, but these vary so much that it is hard to recommend.

Control circuit - consider the available power (volts and amps) at your site, as well as a good ground not connected to wall ground - consider driving at least a 4 foot long copper rod into the ground as close to the coil as possible. You may be able to substitute a drain pipe or large copper sheet. Keep electronics on different circuits, or better yet, not plugged in. Good practice puts an RF choke, lightning arrester, or similar device across the wall input to prevent TC high frequencies from backfeeding into the line. To protect your HV transformer from the higher voltages in the TC secondary, put a "Terry Filter" across the HV out. Power switching should at minimum include a deadman switch - must be held closed to provide power to the HV circuit. Don't work on them alone, or when it's wet.

Capacitor - the simplest by far is the Geek Group bucket capacitor: one clean 5 gallon bucket with lid. Fill with one dozen long neck 12 oz. bottles (IBC root beer works, don't do like I did and wander roadsides collecting beer bottles - new bottles last better, with less awkward explanations). Cook up some brine - as much ordinary salt as you can dissolve in boiling water (watch the cookwear - brine is corrosive in some pans, and plastic containers will taste of salt forever after). Fill bottles 2/3 with brine, and the same depth around the bottles. Top off bottles with mineral oil (best, motor oil will work as well), fill interstitial space to same level with oil. Make u-shaped wires (scrap 12ga copper works) to connect all the bottles. Two long wires make the two leads to the capacitor - one in the bottle network, one in the space. Put the leads through the lid at a suitable distance apart from each other, then seal lid. Store with leads shorted, as caps can spontaneously build up charge. Build a jumpstick for discharging - 5 feet of polyurethane coated pvc pipe with a conductor on one end. Cap design is 'rated' @ ~12 picofarads and 80,000 volts. Test capacitance value with multimeter or test circuit.

The geometry of the primary, secondary, and top load will depend on the components above. Primaries are typically 8-25 turns of copper tube or heavy wire - I've used 1/4" wire - in a flat or helical spiral. Secondaries are hundreds of turns of enameled magnet wire in a 3 to 5:1 aspect ratio on a sealed form (the same urethaned pvc pipe is a favorite). Dryer duct, chicken wire, any metal conductor can be formed into a top load.

To calculate the resonant design of your coils from the other components, I use this:
http://classictesla.com/java/javatc.html
It's a little daunting, and can take several minutes on old browser/pc combos. Basically, you try to match the resonant frequencies of the secondary + topload/ground circuit to the primary/capacitor circuit (frequently called the tank circuit).

http://www.pupman.com/ - Home of the Tesla Coil Mailing List - search the years of archives for questions.

That's a lot to get started with - go find a bucket, 12 bottles, a microwave or neon sign transformer and go!

Whirlwind updates

Lots happening here. QCtech.org has bylaws and officers (yours truly as secretary), the google fiber promotion continues, we have a physical location for a hackerspace and more interested persons at Hamilton Tech. Had a chance to see some old friends for games and impromptu lockpicking session in Chicago last weekend. I also managed to make it to Pumping Station One to look around and talk to one of the founders. The weekend before was spent at a research meeting in Champaign, plus more meetings with friends, professors, etc. All of this stuff needs to get written down at some point for reference.

Don't forget to drop by the hackerspace Friday for more demolition, and Saturday for Build Day 2.0!

Happy Geek

QC2600 was a great success. Five people showed up for lock picking practice and discussion. Servers, rockets, and milling machines also made appearance in conversation. But the big news of the night: Hackerspace plans are in the works. If you're the Quad City Hackie Shack, please find us at qctech.org, we want to hear from/join/assimilate* you.

So, what's a hackerspace and why should you care? A hackerspace is like a YMCA for your brain. It's a never-ending science fair, crossed with a renaissance fair, crossed with a machine shop, crossed with an art studio. A place to put your crazy ideas into tangible form. A public place. A club.

Interested? Hit us up at http://qctech.org, and let's make stuff!

*We're not cyborgs. Honest.

March events

Quad Cities 2600 meeting this Friday, March 5. 5-8pm, Cool Beanz Coffee House.
Hack Day 2.0 will be happening March 20, 9am-midnight, at 1207 95th Avenue West Rock Island. Show up at both, bring your friends, projects & cool ideas.

Hack Day Roundup

Hack Day was a success, thanks to all of you who were there.
Eight people showed up to work on a 3D printer following this design, lockpicking, new board games, various server builds, chemistry, and more. Most important, we made social connections to cross-pollinate ideas and get inspired for more projects yet. Want to host one, or just work on cool projects? Leave a comment, and help us have more of these.

Advocacy: Go visit the Quad Cities Tech Consortium and help us bring Google Fiber to Davenport!

Hack Day Open House

This Saturday, I'm opening up my house for a day of making stuff.
Justification: It's cold out, and there's a limit to the mess they'll let you make in a coffee shop.

Details:
1207 95th Avenue West Rock Island IL 61201
Saturday, February 20, 2010 from 9 am - 7pm (times approximate, show up for any part)

Free parking in the street. I'll have snacks/drinks out all day. Residential internet access available wired and wireless. Several old workstations with WinXP/Debian and dev tools, some exotic hardware including SUN, SGI, Alpha Hand tools, Dremel, soldering iron, lock picks, some high voltage gear, other miscellany available for use.

Bring:
your selves, interested friends and family
your projects, technology, questions, interests, skills, etc.

Some specifics:
I'm looking for more junk printers, servos, stepper motors, and related for 3D printer work.
You'll likely want your laptop/phone
Food and drink, if you wish.

Got a project in mind? I'll post any ideas I'm sent here to help gauge interests.
Got a question/request about the setup? I'll try to accommodate.

Game Controllers as 3D Input Device

This is a cheap hack, but may be useful to you. I use 3D CAD programs frequently. Navigating three dimensions with a 2D interface (mouse) is annoying. The UI in Pro/E, for example, requires either clicking different modes to pan/zoom/rotate, or holding various key+mouse click combos. The interface is improved by something like these.

You can achieve much the same effect, however, with any USB game controller with two analog thumbsticks. I used a knockoff Xbox controller and joy2key to map the controller inputs. I've set left analog stick to rotate, right stick to pan, triggers to zoom. Now I can perform fly-throughs in one motion.