Capacitor Requirements

Now that we have our power source determined, we can figure out what size our capacitor needs to be. First, we need to get the impedance value for our power source so we can plug that into the equation for calculating capacitance:

• Output voltage (V) : 12000 volts
• Output amperage (I) : 0.03 amps
• Calculated impedance (Z) : 400000 ohms (Ω)

Next, we'll plug the Z value into this equation:

• Frequency (f) : 60 hertz (Hz)
• Capacitance (C) : 0.0066 micro Farad (μF)

Transformer, Check!

I unexpectedly procured the keystone piece of the project today while driving back to work from lunch. Going down Lamar, Wes pointed out that there was a neon sign store. We turned around to check it out and discovered a very cool, local mini-manufacturer and repairer of neon, Hayward Neon.

Neon sign transformer for Tesla Coil project

We made acquaintance with the owner's assistant, Mitch, and let him know that we were seeking out a used transformer for a Telsa Coil project. Lucky for us, they happen to have an old-style unit (sans GFCI) that was about six years old but in great working condition rated 12kV @ 30mA. He had us come back into the workshop area to show us the unit while he tested it so we could see for ourselves. He offered to add on a plug, switch and wires while we chatted about how he came to work in a neon shop.

Final cost for this first piece was $64.95, much less than what I was finding online for the same power rating and he said we could bring it back and exchange it towards the cost of a 15kV unit if we decide to make a larger one in the future. Not the free, throw-away I was aiming for but this unit will definitely give us enough power to make a sweet, first coil!

This is where the wires attach

12k volts at 30 mA