Andy Hall wrote:

Something to prevent pitting and destruction of the relay contacts?

Yes, that wouldn't be a bad idea - another cap across the relay contacts
switching the coil - in fact, a car ignition cap (condensor) would be
perfect.


I wonder about the RFI aspects of all of this as well. Do commercial
units have relays or semiconductor switching, I wonder?

We've had both types. Strangely, the relay ones last quite a bit longer.
Poor heatsinking on the switching semiconductor I suspect.


Although this isn't quite in the league of Tesla machines able to
compete with North Hessary Tor, a relay banging away into a coil is
likely to generate enough RF to be a nuisance in populated places.

The capacitor should bring the level down to car-emissions levels I'd
have thought.


--
Grunff