Tesla Coil Mini


Here is our Mini Tesla Coil project. We built it because my boys want a tesla coil demonstration at their school. It only draws 15 watts and uses 12 vdc input so we can battery power it. The primary, secondary, toroid and tank cap are on the upper level. The rotary spark gap is on the right side. The flyback power supply is on the lower level.

The coil resonates at ~2 mHz and requires about 15 watts of power. Streamers are 3 to 4 inches in length.


Operating Set-up

We enclose the rotary spark gap during operation so that the light from the gap does not interfere with our ability to see the streamers. An 8" dia pvc pipe with a cover drops over the RSG. Pictures and descriptions of the components follow.

Power Section

The HV power supply is a contemporary TV flyback with the internal diode intact. It charges the tank cap directly to 12 KVDC with pulsed DC as we have no filter caps in the cicuit. The flyback is driven by a homebrew transformer constructed from ferrite E-cores. The circuit is oscillated by the familar single transistor flyback method. The feedback winding is on the transformer, not the flyback. The transformer steps up the voltage from 12 Volts to 120 volts to drive the flyback. This is necessary because we are driving the flyback's original primary.

Capacitor Top

Tank Capacitor

The tank capacitor is an 1.8 nF parallel plate capacitor constructed from aluminum flashing for the conductor and polyester sheeting for the dielectric. Here you can see the uppermost aluminum plate of the cap and the polyester sheets beneath it.

More Tank Capacitor

The layers of aluminum plates and polyester are visible here.

Capacitor Side

Rotary Spark Gap

The rotary spark gap consists of two tungsten electrodes. Brass screws mounted in a polycarbonate disc pass between the electrodes and close the circuit. The motor operates at 58 RPM and there are 16 brass screws in the disc. This gives a spark gap break rate of 15 BPS.

Tesla Primary, Secondary & Toroid

The Secondary is 5/8" Dia X 7" lg on a PVC Pipe(1225 turns of #36 ga wire). The toroid is made from a 2.1" dia doorknob. It is 1" tall. The primary is 1-3/8" dia and 9 turns of 16 ga wire.

Secondary & Toroid


Unfortunately, the pictures don't do justice to the actual results.

Click Here to return to TeslaBoys Home Page