Homebrew PCBs

----- Original Message ----- 
From: "Dwayne Reid" <dwayner@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, October 13, 2006 5:25 PM
Subject: Re: [Homebrew_PCBs] Mercury lamp for UV exposure


> 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.

Yes, I checked that.

>
> 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.

That's a good idea, I think I'll do the same. I've got a ceramic socket for 
the lamp.

Leon
--
Leon Heller, G1HSM
Suzuki SV1000S motorcycle
leon.heller@...
http://www.geocities.com/leon_heller