Pumping out 30,000V on a dining room table
As often happens, I stumbled upon an interesting video:
I knew about tesla coils, but had never seen one that could play music. I needed to know how it worked. The answer: by replacing the traditional spark gap (acting as a crude switch) with a transistor, I could switch the coil on and off at a rate modulated by an audio signal.
As an added bonus, with this design the device can be shrunk considerably - since a transistor provides the alternating current to the coil’s primary winding, a small DC power supply can be used in place of a bulky mains transformer. I never felt compelled to build a large-scale tesla coil, but a small tabletop-sized one would be fun to have.
A (somewhat crazy) experimenter in Slovakia has documented his SSTC build (based upon an earlier design), and I used this proven design to build my own.
The circuit is straightforward, but required a few components I did not have on hand.
For the secondary coil, I needed insulated copper wire with a diameter of 0.25mm:
For the high-voltage transistor, I needed an IRFP460:
Because of the novelty, I followed the original build and used a Russian high-voltage disc-style power capacitor:
Along with some high-voltage film capacitors:
In order to wind the secondary coil, I needed a 6.3cm diameter pipe with a height of at least 13.5cm. I modeled a tube (with an extension) in 3dsmax and printed it out on an Ender 3:
And lastly, to power everything I needed to deliver up to 8A at 30V from a DC power supply:
Since this build was thrown together with parts on hand, Manhattan Style seemed appropriate. I attached the transistor to a spare heatsink (with some thermal paste), and attached the potentiometer and knob to a scrap 3D-printed panel (leftover from a previous build).
Winding the secondary coil was tedious work, but was successful. A copper spike was added to the top of the coil to control where (and how) the arcing occurs:
The end result looked sketchy, but worked great:
The tabletop tesla coil is capable of putting out arcs a few cm long: