My First Tesla Coil

How it all began... In the spring of 1997 I ran into some classmates in the electronics lab at DeVry Institute (Ohio) that were talking about a Tesla Coil. Since I had seen one in my vocational school I stopped and talked to them. After not too long we decided to work together to build a small Tesla Coil. My vocational teacher Mr. Wahl had given us some simple plans to make a small coil. We began work on the project immediately. The group had grown to four strong; Tristan (me), Chris, Joe, and Garrick. We scrounged around and got most all the parts for free. By the first weekend in May we had the coil ready to run. Here are the specs.

Coil 1 (revision 1)
-   10kV, 23mA OBIT (oil burner ignition transformer)
-   safety gap
-   salt water capacitors, two buckets with Mountain Dew Quick Slam bottles in each, 6 bottles to the bucket, both buckets in series
-   2 gap static gap made out of three long bolts with washers for the gap
-   1/4" copper tubing primary, helical coil, 5 turns, tapped at 2.5 turns
-   secondary is 3" PVC wrapped 15" with #22 AWG magnet wire, topped with two small metal salad bowls stacked like a sphere.

Maximum spark length was about 5"
Not quite as good as we would have liked but it was great anyways!

Throughout the next couple months we made some improvements. I acquired a 0-140VAC 7.5A variac at the Dayton Hamfest. We also tried a larger top load (the next size larger salad bowls), retapped the primary to 5 turns, and used three OBIT's. The maximum spark length was about 9".

Unfortunately, I have no pictures of the first coil as it was when we first built it.

Revision 2

After not too long I found all the great resources on the internet about Tesla Coils, including the Tesla List. I started to learn just how the coil works and how it could be improved. I began modifications that made the coils performance jump drastically. I obtained three 'doorknob' style capacitors from Dr. Resonance, which are actually pretty cheap and I didn't have much faith in them. I also built a new 'Richard Quick spark gap'. Allied Signs generously donated several used neon sign transformers. So, with all the new equipment, spark length increased to about 15" - 20".

Here are some pics of Revision 2 (pics taken 11/97). Click to make 'em big.

This is what happens when you set the coil to resonate at the quantum harmon Specifications of Quantum One Revision 2:

Transformer: Neon Sign Transformer, 12,000V 60mA output

Primary Capacitors: .012uF (total) rated at 30kV

Primary Coil: 1/4" copper tubing, vertical helical wound, 5 turns, tapped at end

Main Spark Gap: 6 gaps in series, .03" between each

Secondary Coil: 3.5" PVC tubing, 15" high, and close wound with #22 magnet wire

Secondary Terminal: 2 metal salad bowls making a spherical shape

Miscellaneous: we used #8 AWG copper wire for all hookups, and #6 AWG wire for ground lead. Secondary coil is coated with a few coats of polyurethane.

Yet another revision...

Revision 3

I was on a quest for perfection (like the Borg?). Never mind. Perfection is still a long way away... but this revision did bring it much closer.

I figured that the coil would probably perform better with a much larger top load, but the primary coil was to small. We also had terrible arcing problems with this primary coil, so we built a new primary. It is a flat spiral coil of about 15 turns of #12 AWG wire, about 1/4" spacing. With this new coil we could put a big 6" diameter 22" wide aluminum ducting toroid on it or the even bigger 8" x 21" stovepipe toroid on it. This big toroid dwarfs the little coil! With either of these toroids maximum spark length increased to 29"!

Here are some pics taken October '98. Click on them for a full size picture.

The spark gap in the last picture is new also. It is a 'Richard Quick' style spark gap with multiple contacts and also forced air cooling.

Here are some shots of some interesting arcing that I noticed in some of the pictures:

This shot shows that the electrical connection between the top of the secondary and the toroid came loose and current was jumping about a 1/4" between them. Click here to see it. Funny that the arc length was still near the maximum 29" length.

This shot is cool! Click here to see it. The first arrow points to an arc that is several feet away from the action. It is jumping between the ducting and the metal trim of a doorway. The second arrow points to arcs that shoot along the wall when the streamers hit the wall.

Specifications of Quantum One Revision 3:

Transformer: Neon Sign Transformer, 12,000V 60mA output

Primary Capacitors: .012uF (total) rated at 30kV

Primary Coil: #12 AWG wire, flat spiral, 1/4" spacing, multi-tap points for various top loads

Main Spark Gap: RQ gap with about 12 gaps, variable spacing & variable tap, forced air

Secondary Coil: 3.5" PVC tubing, 15" high, and close wound with #22 magnet wire

Secondary Terminal: 8" x 21" stovepipe elbow toroid (shown), also 6"x22" aluminum duct toroid

Miscellaneous: we used #8 AWG copper wire for all hookups, and #6 AWG wire for ground lead. Secondary coil is coated with a few coats of polyurethane.

And another...

REVISION IV Revision IV introduced a new secondary coil. I had been told that the original secondary was too low in turns and inductance. I had built it before I new of the great resources on the web for Tesla Coils. So I stepped up to a 4" diameter PVC tube and wound it with smaller wire, #28. In the end it seems that the wire was mislabeled and is smaller than #28. I measured the resistance of the secondary and it seemed to be twice the calculated resistance. Performance was about the same as the previous revisions, but I couldn't put as large of a top load on it due to the much higher inductance, and not enough turns in the primary. I also have a severe problem of multiple secondary flashovers. It seems that the wire is just too small? Sometime I will coat the coil in polyurethane to see if the flashovers stop, and also wind a bigger primary coil. But these improvements are on hold, and I am winding a new secondary instead. It will be 4" PVC with #24 wire. Should be done soon!

Here are some pics (click to make bigger):

Specifications of Quantum One Revision 4:

Transformer: Neon Sign Transformer, 12,000V 60mA output

Primary Capacitors: .012uF (total) rated at 30kV

Primary Coil: #12 AWG wire, flat spiral, 1/4" spacing, multi-tap points for various top loads

Main Spark Gap: RQ gap with about 12 gaps, variable spacing & variable tap, forced air

Secondary Coil: 4" PVC tubing, 16" high, and close wound with #28? or 30? magnet wire (see explanation in the descriptions above.

Secondary Terminal: 8" diameter Van de Graph sphere

Miscellaneous: we used #8 AWG copper wire for all hookups, and #6 AWG wire for ground lead.

This webpage originally born on 3-14-98. Last updated on 11-16-05

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