"Bob Milutinovic" wrote:


It's an air-cored transformer in its simplest form, with absolutely no
"smarts" in the base unit - meaning you'll have 50Hz emanating from the
base.


Interesting...

I always assumed that things like that did just drive a coil at the
mains frequency, and I was a bit surprised to discover that was not
the case for a couple of torch/nightlight combinations we have. I did
not bother to try to trace out the circuit, but it comprises bridge
rectifier, capacitor, a high-voltage transistor and not much else that
I can remember besides the coil.

A coil placed nearby one of those sniffs out a 23kHz signal.

These toothbrushes are obviously different. I wonder what make them go
down the one path vs the other?


Andy Wood