Oct. 9, 1962: First Visible LED Is Demonstrated

I hadn't realised visible LEDs were introduced that long ago. First I saw one live (as opposed to a photo of one) was in '72. A little red one. Later I bought a red and a green one (more like yellow-green, and very dim) for something like $5 for the red and $10. I still have the green. Amber and yellow LEDs came out later and, for a long time, you were pretty much stuck with Red, Green and Yellow/Amber.

I know NASA was using seven-segment LED displays as early as 1969. Several hundred dollars per digit for the commercial version.

Saw my first blue LED in 1985. Paid sixty bucks for it, too (it was actually more, but they made a mistake in the quote). 'Twas a Siemens silicon-carbide LED and 'powder' blue, not the saturated, actinic blues you see today. Peak reverse voltage was 1 volt, forward voltage about 4.5V at 30 mA, and the polarity markings on the package were backward (the flat indicated the anode) - a recipe for disaster and I nearly fried the thing as a result.

Hughes Aircraft Company was using BLUE LEDS in the 1982-4 timeframe (from Cree and Panasonic as I recall) as "point" calibrations of spectral imaging sensors.