led's

ns are not

determine

total

Ahh, but it's those electrons on the far end of the exponential 'Boltzmann tail' that have enough extra thermal energy to make it into the depletion r egion. (I'll have to try I-V curves for LED's at low temperatures someday, dunking into LN2 should be pretty easy.)

George H.

--- If, over a specified temperature range and with exactly 3V across it, the current through the LED was lower than or equal to the specified maximum, the no resistor would be needed.

---

--- If the sum of the voltage drops was less than 5V, then 5V might overcurrent the pair.

---

--- Vsupply - Vled Rs = ---------------- Iled

-- JF

There is no "3V LED"

You don't. Practically no current will flow, no visible light will be generated, ant it will last forever!

See above.

ps - it would help if you learned some basic electronics.

You don't make any sense.

Do you have a real name?

Well, now you're talking about physics and science and stuff like that.

Seems to me that you need X volts to make a photon of X electron-volts energy. Can thermal energy bootstrap an electron to make a photon that's more EV than the voltage across the junction?

Modern LEDs are remarkable gadgets. It would be fun to explore the corner cases, "someday" as you say.

We're currently experimenting with cheap (like, $12) semiconductor lasers to find some that accidentally make clean picosecond light pulses when whacked by one of our laser drivers. The manufacturers certainly don't know if they might. Most laser data sheets are pitiful.

Just spent over a grand on Thorlabs hardware to hold a laser in place and get some of its light into a fiber.

OK, show me a data sheet for a "3 volt LED."

Yes.

-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.

Just guessing.... :)

I googled "1mA LED", not

-- @~@ Remain silent. Nothing from soldiers and magicians is real! / v \ Simplicity is Beauty! May the Force and farces be with you! /( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686 ^ ^ 21:00:02 up 1 day 21:25 0 users load average: 0.08 0.05 0.08 ???! ???! ???! ???! ???! ???! ????? (CSSA):

... and found this link:

Avago Technologies Red non-diffuse round LED,1mA 1.6V

Is it the one you were talking about?

He might be right.... Scroll down for the table in the following link:

This link is actually quite useful to people using LEDs. Too bad it's Japanese...

-- @~@ Remain silent. Nothing from soldiers and magicians is real! / v \ Simplicity is Beauty! May the Force and farces be with you! /( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686 ^ ^ 21:00:02 up 1 day 21:25 0 users load average: 0.08 0.05 0.08 ???! ???! ???! ???! ???! ???! ????? (CSSA):

nn tail' that have enough extra thermal energy to make it into the depletio n region. (I'll have to try I-V curves for LED's at low temperatures somed ay, dunking into LN2 should be pretty easy.)

Grin.. well lots of electronics looks like a branch of science to me.

ergy.

than

There was some news 'splash' from (maybe) mit of someone getting more light out of an led than power in.. at some ridiculously low current.

(The good thing about electrons is there are a whole lot of them, so there are a few with many kT's of kinetic energy.)

There's also this 'common' physics demo where they look at the led wavlengt h and forward voltage drop for a bunch of different color leds and plot thi ngs up to get a measure of Planck's constant. (A bit of a bogus experiment when you look at the details.)

cases,

to

ed by

might.

get

Ouch.. the only thing more expensive than optics is high vacuum.

Speaking of modulating diode lasers, Cliff Stoll (who's quite a lovable 'ch aracter'.) Was visiting the other day. He does a bunch of educational out reach and uses a modulated diode laser, beam splitter, and cheap corner cub e reflector to measure the speed of light. But what he needs is a cheap (f ast) photodiode detector. I put him on to Phil's book... but I've been thi nking it might be a nice project.

George H.

If you read a few Ham related articles - most operators who publish articles put their call sign in the intro.

Its well worth googling any call signs, many operators have websites loaded with projects & circuits.

Those are not "3 volt leds." Their typ forward drop is 3.2, but they are still not shown as being voltage operable; they are spec'd at 20 mA.

If red is the same color as green, yes.

Phil is fond of ebay APDs, which are apparently surplus from some expensive projects. How fast do you need? Pulse or sine wave?

Have you ever touched a real one? :)