LED

[[email protected]]

Hi.I want use 220 volt AC 50 Hz that turn on 2 or 3 LED.How can I do
that

 

[Brendan Gillatt]

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Hi.I want use 220 volt AC 50 Hz that turn on 2 or 3 LED.How can I do
that

Buy some 220 volt rated LEDs.

Alternatively use V = IR to calculate the required resistor value for the
voltage drop required.

http://ledcalc.com/ is nice.

- --
Brendan Gillatt
brendan {at} brendangillatt {dot} co {dot} uk
http://www.brendangillatt.co.uk
PGP Key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0xBACD7433
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[Rich Grise]

Hi.I want use 220 volt AC 50 Hz that turn on 2 or 3 LED.How can I do
that

Verrrrrrry carefully...

http://www.google.com/search?q=LED+tutorial

Good Luck!
Rich

 

[John Fields]

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Buy some 220 volt rated LEDs.

Alternatively use V = IR to calculate the required resistor value for the
voltage drop required.

 

[Spehro Pefhany]

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

 

[John Larkin]

Hi.I want use 220 volt AC 50 Hz that turn on 2 or 3 LED.How can I do
that

Wall wart, as you value your life.

John

 

[default]

Hi.I want use 220 volt AC 50 Hz that turn on 2 or 3 LED.How can I do
that

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.

 

[John Fields]

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

 

[donald]

How can I do that

Another gmail loser.

 

[mpm]

Hi.I want use 220 volt AC 50 Hz that turn on 2 or 3 LED.How can I do
that

Use a CT. (current transformer.)

Does it have to be LED?
How about incandescent?

 

[Spehro Pefhany]

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