Graphs of current vs voltage (or power) for incadescent bulbs?

HTH

Charles

I simply can't resist commenting on this.

The Wien-bridge circuit is named after German Professor Max Wien (1866 - 1938), whose name is not spelled Wein. (Wien, pronounced "veen", is how the city of Vienna is called in German, whereas Wein, pronounced "vain", means wine.)

Consult for more information on Max Wien.

Did your "intermittent" bulbs show this effect only when used in the Wien-bridge oscillator? Then your oscillator may have suffered from "squegging", a common problem when these circuits are run at higher frequencies and at low lamp power.

Best regards,

Martin.

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I'm sorry, I misspelled it. I'm usually very careful about that because it P's me off that I have to do searches with both spellings to get all the hits on the web. i'm a bit out of sorts right now.

The lamps were intermittent and could be measured on an ohmmeter, as the bulb was plinked wsith the finger.

A much better match is: Wein, pronounced "vine", means wine. Sorry.

Austrian pronunciation is often quite different from Prussian... and if you take Yiddish too, which is a dialect of German with Hebrew and Slavic words thrown in, 'vain' is probably quite accurate. Vayter, nokh un gletsl vayn... oy!!

Paul Burke

A subminature Variac with a little guy to twist the knob....

Many years ago, the use of a simple pilot lamp was common to regulate current to crystal oscillators and maintain the gain in precision sine oscillators. The filament resistance is almost linear with a positive tempco from cold until just before the lamp just begins to glow. As the lamp glows brighter, the resistance grows by a factor of 10. Lamp life is reduced by something like the fifth power when you go beyond the rated voltage.

I did not read these sites, but I surely thought that 11th power was a little on the optimistic side of reasonable for life as a function of voltage, with "usual figures being around 12 to 13, and "alarmist" citable figures being 14 and even 16! And that this went both ways when the lamp is not a halogen one.

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As for disadvantage of designing incandescent lamps to last longer: Suppose you got for free some magic lossless transformer to feed your 120V lamps 110V from a 120V line:

These lamps would have power consumption reduced by about 12% and light output reduced about 24, maybe 25%. Increase your electric bill by almost

How about some numbers guessed by me: You originally had a 60 watt

The 75W 120V one at 109V should typically last, using -13 as an exponent, about 2600 hours. The 120V 60 watt 870 lumen one typically is designed to last 1,000 hours at 120V. Over 1,000 hours, that extra 5 watts of electric power consumption, at USA typical rate of 10 cents per KWH, costs 50 cents. If lightbulbs cost

There were congressional hearings sometime back, I believe in the 1960's or the early 1970's, into the "short" design life expectancy of "regular" A19 120V lightbulbs. It turned out that designing filaments to run hotter, even to the pouint of lasting only 1,000 or 750 hours, was economically justifiable even if no value was placed on labor for replacing lightbulbs.

- Don Klipstein ( snipped-for-privacy@misty.com)