Light bulb noise reduction on Hot Plate?

[Chuck H]

Does anyone know how this circuit works? I suspect it's old technology as opposed to new. I can't find a president with any searching.

TIA

Chuck

[Steve Conner]

It uses the bulb as the bottom arm of a voltage divider. The temperature-dependent resistance of the filament makes it act as an expander. See figure 1.15 here:

http://books.google.com/books?id=DoU...rm5Nw#PPA17,M1

The trick has been around since the 1940s if not before. HP used it to stabilize audio oscillators in the 1950s. It's also the mirror image of the light bulb compressor circuit used to protect tweeters in PA cabinets (shown in figure 1.14)

[tubeswell]

I can't find a president with any searching.

How come is it that you just cain't find good president when you need one...

[Steve Conner]

Don't ask me, we're not even a republic.

[jrfrond]

It uses the bulb as the bottom arm of a voltage divider. The temperature-dependent resistance of the filament makes it act as an expander. See figure 1.15 here:

http://books.google.com/books?id=DoU...rm5Nw#PPA17,M1

The trick has been around since the 1940s if not before. HP used it to stabilize audio oscillators in the 1950s. It's also the mirror image of the light bulb compressor circuit used to protect tweeters in PA cabinets (shown in figure 1.14)

It was also used as a "poor man's squelch" in old ham radio sets.

[Chuck H]

Ok. Even I have to admit that was funny. I meant precedent. Not president. I hate when people get angry because they're embarassed. Good thing for me I'd rather be corrected than wrong.

Thanks for all the replies. Now that I know where to look I should have better luck finding. The concept seemed to be older technology to me because of the clever use of rudimentary componants.

Chuck