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  1. Newsgroups: sci.electronics
  2. Path: sparky!uunet!paladin.american.edu!howland.reston.ans.net!bogus.sura.net!udel!sbcs.sunysb.edu!insti!danube
  3. From: danube@max.physics.sunysb.edu
  4. Subject: Starting a mercury lamp
  5. Message-ID: <C1FvCx.6y8@max.physics.sunysb.edu>
  6. Organization: Institute for the Theoretical Physics
  7. Date: Tue, 26 Jan 1993 02:10:09 GMT
  8. Lines: 35
  9.  
  10.    Hello again.  More problems with my current research.  I need a UV
  11. source.  I have a used Mercury lamp, said 250W before I took the envelope
  12. off.  Inside is a quartz tube with two electrodes sticking into each
  13. end and Hg blobs on the sides of the tube.  There is no filament between
  14. the electrodes in the ends as in the ususal flourescent bulbs.
  15.    On one end, the two electrodes are connected to the AC via a 15K (?)
  16. resistor, i.e. hooked up like a little glow lamp with a current limiting
  17. resistor.  The other end is simply connected to the AC, through what
  18. was a filament of some sort before I evaporated it.  See the diagram
  19. below.
  20.     My question is, how is this lamp supposed to work and how can I
  21. get it going without blowing fuses?  
  22.  
  23.  
  24.  -------------------------------------------------------------------------|
  25.     |           |                                                         |
  26.     |           /                                           "filament"--> )
  27.  110 V          \ R         --------------------------------------        (
  28.    A.C.         /         |                                      |        )
  29.                 \         |                                      |        (
  30.     |            |________|____                              ____|___ nc  |
  31.     |                     |                                      |        |
  32.  ---------------------====|====           Hg vapor           ====|====----|
  33.                           |                                      |
  34.                           |                                      |
  35.                            -------------------------------------- 
  36.                                       Quartz tube
  37.  
  38.  
  39.    I've tried replacing the "filament" with two 100 W bulbs to limit 
  40. current, but cannot get the lamp to go on reliably and it probably also
  41. limits the useful power.  Is one supposed to use a ballast in series with
  42. this type of lamp?
  43.    Thanks in advance for your reply.
  44.                             Danube
  45.