LED'S USED AS RECTIFIER DIODES.....

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Chris Smith
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Post by Chris Smith » Thu Oct 19, 2006 8:26 pm

The learning curve is on hi, and still nothing has been inputted... What’s new?

NADA


Oil on a slick on a worn tire seems to be the theme here...lots of noise, zero corrections or accuracy...ZZZZZZZZZZZZ
No balls, just mouth.

Children at play!

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Bob Scott
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Post by Bob Scott » Thu Oct 19, 2006 8:32 pm

Hi Ron! I've missed your wisdom.

We must all agree that we're uneducated young fools compared to Chris's mighty intellect, even if we each have over 30 years of experience and documented education.

Chris has this need to get in the last word. Watch.
Chris Smith wrote:Such silence and errors, over and over and over. Duhhhaa

Must be time for a snooze, the amateurs speaking.

Grow up little child of naieve,....Getting it wrong must be soo right, said the resident in the WH, just like you?

Feel good, getting it all wrong? duhhh

Huddle, its your only savior,...little sheep
Dear Cleburne,

I think I hear your Mommy calling. BTW, she told me that you really think George W. is the best leader since Dick Nixon.

Bob :cool:

rshayes
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Post by rshayes » Thu Oct 19, 2006 8:37 pm

Those who can't learn to write a clear sentence in their native language after 50 years should avoid mentioning learning curves.

Ron H
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Post by Ron H » Thu Oct 19, 2006 8:42 pm

Bob Scott wrote:Hi Ron! I've missed your wisdom.

Chris has this need to get in the last word. Watch.
Chris Smith wrote:Such silence and errors, over and over and over. Duhhhaa

Must be time for a snooze, the amateurs speaking.

Grow up little child of naieve,....Getting it wrong must be soo right, said the resident in the WH, just like you?

Feel good, getting it all wrong? duhhh

Huddle, its your only savior,...little sheep
Dear Cleburne,

I think I hear your Mommy calling. BTW, she told me that you really think George W. is the best leader since Dick Nixon.

Bob :cool:
Chumming is illegal in some places. I hope we don't get caught. :grin:

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Chris Smith
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Post by Chris Smith » Thu Oct 19, 2006 8:51 pm

Uneducated young fools, grow up piss ant.

Call me in 30 years when you just start to learn, moron child.

Im sure your full knowledge would fit into a teaspoon, with room for the liquids.

Was that degree one speaking, or two?

WHAT? duhhh


Why don’t you describe to us what a Plasmon is, how it is affected in the LED, and how to release more of them with out adding any amps to the circuit,...Ohh Im sorry, was that rocket science for your brain?

Robert Reed
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Post by Robert Reed » Thu Oct 19, 2006 8:53 pm

MrAl,Bodgy
I think its time.

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Chris Smith
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Post by Chris Smith » Thu Oct 19, 2006 8:58 pm

It way past their educated time limit, time for their bed...

Squeek, squeek, squeek, the sound of the unemployed, uneducated, and ignorant here at the forum.

Duhhh Your sound is hallow and with out meaning, unless you’re a sheep?

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MrAl
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Post by MrAl » Thu Oct 19, 2006 11:18 pm

Hi again,

Robert...sorry i missed your previous post earlier...

I dont mean to push the compressor/expander idea but it is a possibility.
I thought we could rule out using the LEDs as a rectifier because of
its reverse voltage spec, which is usually less than 5v. Since the typical
red LED drops 1.7v, this would mean we could only use it for a
rectifier when we want less than 3.3 volts output, and with some margin
of safety even that isnt possible (maybe 2.5 volts output max).
It would be totally rediculous to use an LED in place of a diode
for this kind of thing unless it's for a novelty so you can say you
used an LED for a rectifier :smile:

BTW having a compressor is either a good thing or a bad thing,
depending of course on whether or not you want to use it.
Having a switch to switch it in or out would be nice...this way you
could turn it on when you want it, off when you dont.

Also BTW an LED could be used for the expander section too as you
probably realize already. This would be very good for an amp to have
built it.
LEDs vs Bulbs, LEDs are winning.

Scott Olson
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Post by Scott Olson » Mon Oct 30, 2006 8:25 am

haklesup wrote:
If any diodes did emit a visible glow (way back when) they were not silicon. Only in the last few years with great effort have researchers been able to make visible light Si structures.
Bob Pease had an interesting teaser in his Pease Porridge column years ago (Mar 18.1996). Take an ordinary NPN transistor, reverse bias the base emitter with about 9 volts (1k current limit resistor) and measure the voltage at the open collector; what do you read? The answer, a small negative voltage! I, like most, didn't like the answer. I even made sure it wasn't my digital meter fooling me (I tried an analog meter and saw the negative deflection).

The explanation was that the reverse biased Si junction zeners and emits light, photons go through the crystal latice and cause enough photocurrent in the cb junction to force the collector negative. I didn't like the explanation, so I marched to my stockroom, grabbed a transistor I could easily open (metal can), cut the top off, and looked at it under a microscope. Sure enough, there was light! (You need a microscope to see it).

This is a great teaser question for engineers.

+9v
|
1k
|
E
B - Ground
C
|
V?

Bob said 12 volts, I think I found about 9 to work best.

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philba
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Post by philba » Mon Oct 30, 2006 9:34 am

now that's cool! I had to pull one out and try it. very cool.

keep that kind of post coming. maybe there's hope for this forum yet.

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MrAl
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Post by MrAl » Mon Oct 30, 2006 12:27 pm

Hi there,

That is very interesting yes, but not something i would have done
because a lot of transistors have a max reverse BE spec of 5 volts.
What transistor did you try this with?

Also, what voltage level do you get and how much current can
you draw from it as a voltage source?
LEDs vs Bulbs, LEDs are winning.

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haklesup
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Post by haklesup » Mon Oct 30, 2006 3:49 pm

Well, that's because its not something you're supposed to do but it is a nice demonstration of the photoelectric effect both as an emitter and a receiver of photons in the same device.

Driving a typical junction into Zener breakdown also known as Avalanche breakdown (when not specifically designed to do so as in a Zener diode) is generally a prelude to failure. How long it lasts depends on the amount of current that's flowing which depends on the device characteristics. Failure may be instantaneous or it may handle a modest current non destructively as it appears to do in this demonstration. In any case, I would expect a small MTBF. The transistor may very well be permanently damaged (or degraded) by the experiment.

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Chris Smith
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Post by Chris Smith » Mon Oct 30, 2006 3:57 pm

If you wait long enough, some one intelligent will repeat your words.

[“If any diodes did emit a visible glow (way back when) they were not silicon??â€

rshayes
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Post by rshayes » Tue Oct 31, 2006 2:40 am

I would disagree with Bob Pease's explanation in one respect. I would expect that the electrons would travel through the base before emitting light as they recombined in the collector region. The base is usually extremely thin, and the electrons are being accellerated by a substantial field.

Fairchild made several devices using this type of emission for a couple of years in the late sixties (FLA610, FLA611, FLA630, FLB100, and FLC100). It apparently was a dead end, since they weren't listed in a 1975 catalog.

The spectrum in the visible range is a close approximation to a 2500K black body. The efficiency was terrible. A 10 amp current produced about 1 microwatt of optical output. The zener voltage was about 7 volts, so the efficiency was less than .0000014 percent. This limited it to low duty cycle operation. One suggested application was contact printing on photographic film.

This was not a forerunner for the LED. It used a different, and much less efficient, mechanism to excite the electrons, and the emission wavelength is not related to the band gap of the material.

The point about low reliability is well taken. Operating a base-emitter junction in the reverse breakdown region is know to degrade the matching in closely matched transistor pairs used in differential amplifiers.

Under normal operation, silicon devices do not emit visible light. They do emit an insignificant amount of recombination radiation in the near infrared region. There are papers published in the early sixties describing the measures needed to detect this radiation.

Both Dean Huster and haklesup were correct. The purpose of the black paint or black glass was to reduce the sensitivity of the silicon diodes to light and not to prevent the emission of light.

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Chris Smith
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Post by Chris Smith » Tue Oct 31, 2006 8:16 am

All leds that produced light were the front runners of todays long science of the led.

Its funny how some can claim the wheel made out of stone, isnt the fore runner of todays tire?

I guess if you wish hard enough, anything is possible?

Semantics is best left for others.

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