Nigel said:
For ages i've noticed the neon on my bench power supply
flickers according to what else is in use electrically.
A room lamp if on then neon goes out but as its on a dimmer
and i turn it down to 30% or so or less ,then the neon
comes on. Happens with ordinary filament lamps on
the lighting circuit - the ps is off the power ring main.
Just curious - any ideas ?
I have to agree that the ambient light level must ionize the gas enough to
cause what you're seeing. I've seen another demonstration of that very
effect recently.
I bought one of those little flashlights that have "white" LED's and an
incandescent bulb in the reflector at one end, and a cold cathode
flourescent tube behind a lens on the side of the handle. The switch lets
you cycle between the 3 modes and off.
In any very dark room, the darn flourescent tube will *not* light unless
it's stimulated by a few photons from another source. I've tried reflecting
some of the light out of the end back onto the handle and then switching it.
That works, but it is physically hard to do. A tiny flicker from another
penlight flashlight will cause it to light off immediately, as will walking
into a lighted area. Also the phosphor on my watch face puts out enough
radiation of some kind to help the tube light.
Once it lights the first time it will re-light, at least for a while. I've
not tested to see just how long it stays "hot" enough to work, though.
It sure took me a while to figure it out. I bet that it lit very reliably at
the factory. I'm sure they don't assemble them in total darkness! <grin>
Be well,
Mike D.