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, you can 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.
Let’s build one.
A (somewhat crazy) experimenter in Slovakia has documented his SSTC build (based upon an earlier design), and we will use this proven design to build ours.
The circuit is straightforward, but requires a few components I don’t have on hand.
For the secondary coil, we need insulated copper wire with a diameter of 0.25mm:
For the high-voltage transistor, we need an IRFP460:
Because of the novelty, we will follow the original build and use a Russian high-voltage disc-style power capacitor:
Along with some high-voltage film capacitors:
In order to wind the secondary coil, we need a 6.3cm diameter pipe with a height of at least 13.5cm (possibly more). We quickly model a tube (with an extension) in 3dsmax and print it out on an Ender 3:
And lastly, to power everything we need to deliver up to 8A at 30V from a DC power supply:
Since this build is being thrown together with parts on hand, Manhattan Style seems appropriate. We attach the transistor to a spare heatsink (with some thermal paste), and attach the potentiometer and knob to a scrap 3d printed panel (leftover from a previous build).
Winding the secondary coil is tedious work, but is successful. A copper spike is added to the top of the coil to control where (and how) the arcing occurs:
The end result looks sketchy, but works great:
Our tabletop tesla coil is capable of putting out arcs a few cm long: