The Neon Sign Tesla Coil

I first read about Tesla coils about 5 years ago, and I've wanted to build one ever since. I finally decided to build one in January of 2006

The Tesla coil is a "air cored resonant transformer" which is capable of generating extremely high voltages using a relatively low input voltage. The secret to the immense voltage gain is resonance.

The High voltage transformer (usually a 12-15kV neon sign transformer) charges up the HV capacitor. The capacitor charges up until the voltage across the cap and primary winding is great enough to arc across the spark gap. The arc shorts the capacitor and primary, causing a large amount of current to flow. This large current creates an inductance in the primary which is transferred to the secondary. The voltage across the cap drops and the arc extinguishes. Then the process repeats.

The primary puts a small amount of energy into the secondary every time it fires (arcs). If the circuits are in tune, this energy will build until it breaks down the air and makes lightning. This is similar to swinging on a swing set (but without the lightning...) By putting a little energy in at the right moment, you can swing pretty high.

After many weeks of research and gathering supplies, I was finally able to start construction.

(more detail later once I find the pictures)

After construction, it was time to test

Here's a picture of the coil lighting up a couple fluorescent lights. The RF energy generated was capable of lighting the tubes from several feet away.

Unfortunately, due to a miscalculation, my primary circuit was too small for the resonant frequency of the secondary so I was only able to get a 16" spark instead of 34" sparks calculated. Instead of spending more time redesigning this tiny coil, I decided to move onto the off-line Tesla coil.