James Newton, Host wrote:

>> This relationship probably can be found described in some manufacturer
>> literature, I'd hope.
> 
> Yeah, that's what I figured, but I'll be darned if I can find it in any
> of the literature from at least three different mfgrs. 

I didn't come up with anything either, on a short search.

But I found some other interesting stuff:

- http://www.zeit.de/stimmts/1999/199933_stimmts_gluehbir (German):
Since 1924, an international cartel (?) consisting of GE (USA),
Osram/Siemens (Germany) and Assoc. Elect. Ind. (UK) divided up the world
market between themselves and also defined the "durability point" at 1000h.
Making the filament stronger increases durability by decreasing the energy
efficiency. Chinese lamps seem to be designed for 5000 hours (not part of
the cartel :). Since energy cost is a major factor of the lifetime cost of
a lamp, it may not be beneficial (financially) to increase the lifetime
(see also below). They don't give sources, and the companies probably
wouldn't publish their contract, so this is "leaked classified
information", at most :)

- http://www.wissen.swr.de/warum/gluehlampe/themenseiten/t2/s1.html#
(German):
A nice little toy virtual lab that associates durability, color temperature
and electric power. Doesn't seem to work with the low powers you want, and
doesn't give real numerical results (except for the durability).

- http://freespace.virgin.net/tom.baldwin/bulbguide.html:
Some general info about incandescent lamps. See
http://freespace.virgin.net/tom.baldwin/bulbguide.html#pay for an argument
about why making a bulb last longer may not "pay".



>> As easier methods there are thumb-rule percentage of the rated power, or
>> a thumb-rule resistance increase from the cold resistance. The thumb
>> rules maybe created using the above... 
> 
> I'd be happy with those thumb-rules... You have any idea what they are?
> Or do I have to create them myself?

I think you'd probably have to do something along the lines of what Russell
did. 

I suspect that to some degree the results of what means "off" will vary
with the type of lamp, possibly with the rated power of the lamp (see the
report from Harold; I think that maybe very high power lamps glow with a
lower percentage of voltage or current than lower power lamps), and almost
certainly with the application (environment light). 

Gerhard

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