Hi.I want use 220 volt AC 50 Hz that turn on 2 or 3 LED.How can I do that
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16 years ago
LED
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16 years ago
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16 years ago
Verrrrrrry carefully...
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Good Luck! Rich
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16 years ago
-- What happens when the polarity of the 220Hz mains reverse-biases the LED?
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16 years ago
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
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
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16 years ago
Wall wart, as you value your life.
John
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16 years ago
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.
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16 years ago
-- And goes white when the junction blows? Funny! :-)
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16 years ago
Another gmail loser.
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16 years ago
Use a CT. (current transformer.)
Does it have to be LED? How about incandescent?
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16 years ago
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
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com