Post by @fivetonsflax@tilde.zone

Dan Piponi
@dpiponi @mathstodon.xyz
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The thing that makes modern dimmers for lighting complicated is basically what Einstein got his Nobel prize for.

Replying to @fivetonsflax@tilde.zone
Poul-Henning Kamp
@bsdphk @fosstodon.org
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@fivetonsflax @dpiponi

Very crudely:

Our eyes are "peak-detectors", and since LED's emit monochromatic light, you modulating the LED in time does not dim the light very much in our perception.

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Replying to @bsdphk@fosstodon.org
Poul-Henning Kamp
@bsdphk @fosstodon.org
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@fivetonsflax @dpiponi

This was first noticed during the development of the HP-35 calculator, search for "current" in:

hpmemoryproject.org/wb_pages/j

("White LED" are blue LED with a "phosphor" layer to down-convert to other colors.)

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Replying to @bsdphk@fosstodon.org
Ben Rosengart
@fivetonsflax @tilde.zone
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@bsdphk @dpiponi Wonderful, thank you. And the Einstein connection is that the phosphor layer uses the photoelectric effect? Or … ?

Replying to @fivetonsflax@tilde.zone
Poul-Henning Kamp
@bsdphk @fosstodon.org
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@fivetonsflax @dpiponi

The photoelectric effect is the exact same phenomena as LED light, but in reverse.

Replying to @bsdphk@fosstodon.org
xenotar
@xenotar
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@bsdphk@fosstodon.org @fivetonsflax@tilde.zone @dpiponi@mathstodon.xyz Thanks for the link; I’ve always been curious about the history of HP calculators, the algorithms, and the people who created them. I had early access to an HP-45 as a teenager, and later to an HP-25, where I learned to program with the help of the manual. I have fond memories of HP calculators.