"whisky-dave" wrote in message
...
On Friday, 1 March 2019 16:02:52 UTC, NY wrote:
"whisky-dave" wrote in message
...

Dimmable fluorescent fittings have been around since the early 1960s.
Nothing new there.

How are fluorescents dimmed?

I waqsnt; sure so looked it up.

https://www.etcconnect.com/Support/A...ures-Work.aspx

I'd always thought that it was impossible,

well I knew it was possible but a bit more difficult than just replacing a
light switch with a dimmer switch.


and
was surprised when the fluorescents in my school lecture theatre could be
dimmed. They were probably installed in the early to mid 70s, which gives
an
idea of what technology was available then.

I had a brief look at how the stage lighting in the school worked in the
late 70s, just seemed to be large covered rheostats covered in dust.

I helped with the lighting in the school hall (an older building with a
proper proscenium arch, wings and a curtain) and they used huge wire-wound
rheostats which were operated with a length of wood to fade many up or down
at the same time.

There was also a huge circular drum rheostat for dimming the house lights,
and we were given strict instructions to make *certain* that the big
circular handle was in the fully-anti-clockwise (min) position before
turning on or off (to avoid turning them on/off suddenly) and when we
started to fade them either way, do it *quickly*, taking no more than about
5 seconds to go from one end to the other (accompanied by a loud screeching
of the contact on the wire!) to avoid running the rheostat at part-load for
any longer than necessary. Even then, we could see the wire glowing in the
dim light of the wings where the lighting board was.

The lecture theatre was equipped with lots of theatrical lights, and a nice
"new" (at the time) triac dimmer system with tiny sliders for diming the
lights, but it was never used for plays because there were no wings (other
than exiting through the fire doors either side into the playground) and
there was no curtain.