On Mar 1, 5:04*pm, " wrote:
On Mar 1, 1:53*pm, George Herold wrote: My question. *Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? *(60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. *(Is the
one shown here OK?)

Does yours look like the one in the wiki article? *If so, I would vote
for a value between 100K and 470K. *At 100K, a half-watt resistor
would be marginal, and I would go for one rated for 1 watt. *Within
this range, the value is probably not too critical.

Yes the lamp looks like the picture in the wiki article. If I
believe the curve there, then I've got something like 160-200 volts
across the lamp at 20mA. So I've got (call it) 80 V to drop on the
resistor at 20mA.. I get 3 k ohm at a watt or two. Hmm maybe what
looks like brown black brown is a discolored red black red. (I always
have hated the way red and brown look almost the same on the pale blue
body of the metal film resistors.)

100k seems like it won't allow enough current through to keep the lmap
lite. (But I've never worked with neon lamps.)

George H.