Tesla Coil Control Unit (TCCU) Modifications

Below is a picture of my control unit with the addition of the phase controller for the rotary spark gap. The main control switch is on the top left. Next to that is an analog voltage meter showing the output voltage going to the NST bank. The dial in the middle is the voltage control to the NST bank and the dial to the right is the RSG phase control. There is a small LCD in the middle top for future use as well as a number pad. This was envisioned to be a part of a safety/security control that was plagued with interference issues (the microcontroller reset every time the power was applied to the coil).

With the addition of the rotary spark gap to my tesla coil setup, an update to the control unit was warranted. It started with just the desire to add the phase shifter variac for the spark gap motor and turned into the inclusion of a more robust interface. I replaced the old connectors with a typical outlet for the input power and a high current appliance outlet for the tesla coil power. The outlet on the left in the photo below is for the power to the NST bank and to the RSG motor, each having separate hot and common wires. The outlet in the middle is to power the control unit. This will make for much easier connecting and disconnecting of the unit

Below is a photo of the inside of the control unit. This is the underside of the front panel.

This photo shows the power factor correction capacitor bank in the back right. Total capacitance is 195 uF which is a little shy of the ideal for my power supply (1.8 kVA NST bank). This should still aid in lowering the mains current.

Progress of the Rotary Spark Gap

Procured a synchronous motor made for old Teletype machines so that I can finally build a rotary spark gap. This gap offers superior quenching characteristics and a very repeatable break rate (switch closures) for reliable operation. Also the primary capacitor needs to be increased from a static gap run system when running with a rotary spark gap which will lead to increased spark length from the extra energy storage.

Currently I have the pure tungsten rods (7” long, 5/32” diameter, purchased from McMaster Carr), a bar of Delrin plastic (1” x 1” square by 12” long) that I need to cut to the correct length, and some shaft collars to hold the rod in the Delrin.

I still need to post some pictures and maybe some drawings. I’ll post those soon…

Main Stuff Complete

Here is the final configuration minus the strike protection rail.

New Toroid vs Old Toroid

Finally Finished the Toroid!

Here is a picture of the completed toroid. It only took me about an hour and a half to finish the last third of it. I finally started getting the hang of it!

Side view of the finished toroid.

Toroid Update

Finishing up the application of aluminum foil tape on the toroid is turning out to take a very long time. I am currently at the halfway mark and I have probably spent 6 to 8 hours on that. Making sure that the tape lines up correctly in relation to the previously applied tape is what is taking so much time. Hopefully the last half will go faster since I have a system down. Time will tell...

Toroid Pictures

Here are some pictures of the progress of the toroidal discharge terminal.

Close-up of the mechanical connection point of the toroid to the secondary. This is just a standard plumbing flange.

This toroid is made of 7" flexible dryer ducting formed into a 29" ring. Aluminum foil covered 0.25" plywood is what the center is made from. The ducting has a layer of packaging tape on it to smooth out the rough edges some and then aluminum tape is placed on top of that. In this picture, the toroid is about 1/3 of the way done with the aluminum tape.

This is the partially finished toroid sitting on top of the Tesla Coil.