🚀 go-pugleaf

In article <C1FvCx.6y8@max.physics.sunysb.edu>, danube@max.physics.sunysb.edu writes:
|>    Hello again.  More problems with my current research.  I need a UV
|> source.  I have a used Mercury lamp, said 250W before I took the envelope
|> off.  Inside is a quartz tube with two electrodes sticking into each
|> end and Hg blobs on the sides of the tube.  There is no filament between
|> the electrodes in the ends as in the ususal flourescent bulbs.
|>    On one end, the two electrodes are connected to the AC via a 15K (?)
|> resistor, i.e. hooked up like a little glow lamp with a current limiting
|> resistor.  The other end is simply connected to the AC, through what
|> was a filament of some sort before I evaporated it.  See the diagram
|> below.
|>     My question is, how is this lamp supposed to work and how can I
|> get it going without blowing fuses?  
|> 
|> 
|>  -------------------------------------------------------------------------|
|>     |           |                                                         |
|>     |           /                                           "filament"--> )
|>  110 V          \ R         --------------------------------------        (
|>    A.C.         /         |                                      |        )
|>                 \         |                                      |        (
|>     |            |________|____                              ____|___ nc  |
|>     |                     |                                      |        |
|>  ---------------------====|====           Hg vapor           ====|====----|
|>                           |                                      |
|>                           |                                      |
|>                            -------------------------------------- 
|>                                       Quartz tube
|> 
|> 
|>    I've tried replacing the "filament" with two 100 W bulbs to limit 
|> current, but cannot get the lamp to go on reliably and it probably also
|> limits the useful power.  Is one supposed to use a ballast in series with
|> this type of lamp?

It is supposed to have a current limiting inductor connected in series,
where your "filament" is marked.

As you supposed, the resistor and electrode just form a small discharge
which supplies the ionised gasses needed for the lamp to start.

I would actually connect "R" after the inductive load, not before.

Also, remember that these lamps need time to get going, 10 to fifteen minutes
before it is working at full efficiency.

I would suggest that the easiest method of making it work correctly would be
to go and buy a "security light", and strip out the control equipment for use
in your experiment.

I used to runn exactly the same sort of setup that you are trying, and
didn't have the control equipment (this was for 500 and 750 watt lamps),
so I used a 500 watt electric heater in series ...

Philip