LED

Verrrrrrry carefully...

Good Luck! Rich

The color changes a bit (thermal shift of wavelength before it quits.

I guess you could tune wavelength of a solid-state laser by controlling the temperature.

Best regards, Spehro Pefhany

Wall wart, as you value your life.

John

Calculate the resistance needed to limit the current that the leds you have require - then calculate the capacitive reactance that equals the resistance at 50 cycles and put that in series with the LED - with a rectifier and 100 ohm 1/4 carbon film resistor to limit inrush current as the cap charges for the first time and to act as a fuse if the cap shorts.

Another gmail loser.

Use a CT. (current transformer.)

Does it have to be LED? How about incandescent?

I think it's a shift down in wavelength so a green LED would go yellowish with increasing Tj.

;-) Most semis go shorted unless you really whack them. The reverse breakdown results in a lot of temperature dissipation, of course, maybe 20x that in the forward direction because the voltage is higher.

Okay, I'll look. It's a known technique. See, for example, US 7251261 "Temperature Tuning the Wavelength of a Semiconductor Laser Using a Variable Thermal Impedance" July 1, 2007. I'll leave the foray into solid-state physics to find the physical mechanism for another time, but I'll bet Boltzman's constant is in there somewhere.

Best regards, Spehro Pefhany