BLUE-VIOLET 430nm Gallium Nitride over Silicon Carbide base:
Spectrum of a typical "430nm" blue LED courtesy of Kevin Gilmore and was used with permission.
Radio Shack # 276-0311 Gan on SiC Blue 5mm LED, $3.49
Purchased 02-14-09, tested on 02-17-09
This is a GaN on SiC (gallium nitride on a silicon carbide substrate) violet-blue in a water-clear 5mm epoxy package.
Beam photograph at ~12".
I do not yet have the target at my new Federal Way WA. USA location, so I shot this photograph onto the white wall just to the right of my "BIG SCARY LASER" poster (sent by www.megagreen.co.uk).
Measures 200mcd on a Meterman LM631 (now Amprobe LM631A) light meter.
Vf is 3.858 volts at an If of 19.28mA.
Spectrographic analysis of this LED.
USB2000 Spectrometer graciously donated by P.L.
Radio Shack, blue LED, 276-311
Purchased 06-08-07, tested 06-09-07
No, you aren't seeing things.
Yes, I have already tested this LED. But that was a number of years ago; this LED was purchased in mid-June 2007.
This is a 5mm round LED in a water-clear epoxy case. It produces a (fairly) smooth, mainly circular beam with a brighter hotspot in the center.
Measures 710mcd at a drive current of 19.28mA.
Viewing angle is advertised at 24°.
Spectrographic analysis of this LED.
USB2000 spectrometer graciously donated by P.L.
MYSTERY LED, probable Cree die, 5mm clear case
This is one of several "mystery" LEDs that have crossed my desk in recent months. It is an older style GaN on SiC type, very similar in construction to the
Radio Shack #276-311 blue LED. Its leadframe design and lens parameters are not like the RS part though, and it is not known who made it or who sells (or sold) it.
This LED is approximately 800mcd in intensity, mostly confined to a narrow, 8° central square. This is surrounded by a bright ring artifact, characteristic of many other
narrow-beam LEDs in 5 & 10mm cases.
In this first photo, you see the LED being fired at a predominantly white bookmark from about eight inches away. The second picture shows an effect this and most other
blue LEDs have, and that is to cause fluorescence of certain brightly colored materials. In this case, it is the day-glow blueish green body of a Pelican brand LED flasher.
Day-glow greens, oranges, and greens fluoresce quite strongly in this LED's light; some red materials will also glow in blue light, though usually quite weakly.
The chemical makeup of this LED is the classic Cree design of gallium nitride layers put over a mostly transparent silicon carbide substrate. The silicon carbide is
somewhat conductive of electricity, so this LED has the more
traditional single bond wire attaching to a tiny ball on the top surface of the chip at its center; rather than the two top contacts in the corners
found in LEDs built on artificial sapphire (like Nichia and Toyoda Gosei parts) because sapphire is an insulator.
Until recently, those two-wire chips were the brightest available, but some information I've seen (circa. 11-2001) seems to indicate
that Cree has found a way to make their GaN on SiC LEDs brighter than the competing Nichia parts. Only time (and samples!) will tell though.
Cree 5mm blue, availability currently unknown
This is a blue-violet LED in a clear, 5mm (T1 3/4) style case.
It is very similar to the Radio Shack model shown directly below, except that its beam is about half as wide and I haven't seen these things pop as easily as Radio Shack's have.
They are made with gallium nitride on a silicon carbide substrate; and have a very characteristic color not found in the usual Nichia & similar LED styles.
Use them for indicators, behind switches & buttons, or in musical instruments.
Beam angle is around 15 degrees for this medium-intensity blue-violet LED.
Radio Shack catalog # 276-311, $2.99 apiece.
Radio Shack was one of the first to offer blue LEDs which were easily available to the average Joe.
These are a variation of Gallium Nitride blue LEDs, built on a silicon carbide substrate. Their color is a slightly violetish, slightly whitish
blue, and they are brighter than many other common LEDs, but not nearly as bright as newer GaN types.
I have found these to be much more fragile than most other LEDs, and they seem to fail at the drop of a hat. Any hat.
Static electricity does them in; as does any reverse voltage at any current whatsoever.
These LEDs are useful for hobby applications, as well as for indicators in computers and other electronic equipment.
The deeper blue peak output will cause some dyes and papers to glow as they might under a common blacklight.
These LEDs require 4.4 to 5 volts; which computer power supplies readily give.
The tough silicon carbide substrate doesn't appear to give any
substantial protection against overheating of the chip, so you shouldn't run these at their 30mA maximum rating unless you're
certain you can sink away the extra heat or don't mind replacing them every few months or so when they become too dim.
I've had these go dim after a few months of using them for taillights, they have since been changed out with newer Nichia models.
The one in the dashboard, and a second one in a computer continue to work as well now as they did the day I got them several years (!) ago.
Beam pattern for Radio Shack's blue LED. It has a viewing angle of 30 degrees.
Note these LEDs don't project a really super bright beam like the newer gallium nitride on sapphire types do.
Electronics Goldmine catalog # G9831, 69 cents apiece / 100 for $59.00
This is a small blue LED, size 3mm (T1) with a kind of turquoise tinted, slightly diffused case.
These aren't quite as bright as Radio Shack's 5mm blue, but they seem to work quite well as indicators in household electronics.
The color appears similar to Radio Shack's, but in a very dark room, they appear a little more violetish, or deeper blue.
I installed one in the keychain remote of my Radio Shack remote control switch (cat. # 61-2667A).
It lights up better than the original red LED did, and better yet even than the high efficiency blue LED I replaced the red one with.
Another one ended up in a Supra external modem, and works fine in it.
The price is right too, costing 69 cents apiece. There simply isn't a less expensive blue LED out there.
Out of the 15 I bought, 9 were installed into equipment, 1 mysteriously stopped working during testing, and 5 remain waiting
to be used in something. I will definately buy more of these - as many as I can afford.
They work well at lower currents, and are small and discreet enough to hide anywhere. Surprise!
