bigclive
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Tiny mains powered fluorescent light
🕑 Added 2024-12-11 05:55:24 +0000 UTCThis module was apparently used for panel illumination in older equipment.
It uses an unusual four-electrode system to strike the tube at low voltage. the system is very similar to the self striking mercury vapour lamps used in street lighting and floodlights.
Comments
Mike Weijmans
Nice one for Frans' clocks :)
OJC123
Familiar with that. We hired them in for events but once LED versions dropped to reasonable prices we bought them. Much more flexible.
Big Clive
In the entertainment industry, the professional discharge lamp based moving lights do have a hot restrike feature, but lots of warnings about seriously shortening lamp life if it is used. Normally the lights have a shutter to "turn off" the light, and just run it at lower power while the shutter is in place.
OJC123
Having checked, I think it's the high pressure, caused by the heat, in simple terms I can understand then at high pressure there are more gas particles in the way of the electrons so the path of the electrons becomes more randomised and so a much higher voltage than the fitting can deliver is required to strike an arc. While I was working with it I was only concerned with it being a nuisance rather than why it was a nuisance.
Big Clive
The restrike time applies to many discharge lamps. The electrical characteristics of a hot lamp are very different to that of a cold lamp, and I believe it's harder to initiate ionisation when they are in their hot state. I'm not sure exactly why though.
OJC123
Tangentially related but here goes. This has puzzled me for a long time. I worked in a school built in the late 1950s. The hall lights were mercury vapour lamps about the size and shape of an American football. According to the electrician who retired 20+ years ago, they were in the type of fittings used in petrol forecourts into the 70s. They gave out a sickly blue-green light. I don't think they were self striking because they had a circuit board attached with a capacitor the size of a tin of beans. They took a while to warm up from cold and made quite a lot of noise when starting up. The annoying thing was that once switched off they would not restrike for about ten minutes. If we ever needed to evacuate the audience the problem was that we couldn't guarantee that the lights would come on immediately so we had LED lights installed alongside them not long before I retired. The fittings had a bayonet lampholder in parallel with the circuit board so that a domestic type filament lamp could also be fitted but that didn't cut it for evacuation purposes. Any ideas why the lamps took so long to restrike once they had been switched off? Thanks in advance for any replies.
Major Holdups
21-4-93 on bottom of drawing
Big Clive
I couldn;t even put a date on it. Decades.
Rup (FastAsFunk)
Blimey, that data sheet looks ancient. How long do you think you've had the unit...? I'm merely an interested observer and not an expert but I wonder if it is the sort of thing used in vending machines or such.
