At 03:47 AM 10/13/2006, Leon Heller wrote:
>I've just bought a ballast to go with a mercury lamp I bought on Ebay. I've
>just connected them up and the lamp is working OK. I rather stupidly put it
>on the bed with a dressing gown over it to keep the cat away, smelt burning
>a few minutes later and found the lamp had burnt the duvet cover and the
>dressing gown. 8-(
>
>Next step is to remove the outer envelope and do some test exposures. I'll
>rig up a suitable box to keep the UV away from me.
Couple of things: make sure that the phosphor is on the inside
surface of the OUTER envelope. That pretty much guarantees that the
inside bulb is clear, and thus emits UV.
The reason I mention this is that I now see Mercury Vapor bulbs with
a clear outer envelope. Box usually mentions that the bulb is "UV
safe" - this means that the inner bulb doesn't emit UV.
The other important thing is: that inner bulb needs to run hot. The
existing outer envelope provides thermal insulation so that the inner
bulb can operate at the design temperature.
I wound up enclosing the inner bulb within a Hammond die-cast
aluminum box about 4" x 4" x 7". A large hole on the bottom allows
the UV to escape, a mechanical shutter (motor driven) covers the hole
until the timer switch is hit.
The enclosure allows the bulb to operate near its design temperature:
its air-tight other than the single large hole facing downwards. I
find that the bulb takes 5 to 10 minutes to come up to operating
temperature before I use it (don't really pay much attention to it:
the electronic ballast I use sort of squeals until the bulb reaches
operating temperature).
The whole thing works well - I'm on my 2nd bulb now.
dwayne
--
Dwayne Reid <
dwayner@...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 22 years of Engineering Innovation (1984 - 2006)
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