Mysterious LED

Radio Shack sells a "low intensity" diffused 3 mm red LED that I use as an indicator light on the pc boards I build. I like it because it is more than bright enough when using 0.5 ma.

I haven't been able to find any others that come close to it's efficiency. I've tried various "high efficiency" 3 mm LED's from Digikey but they require at least 5 times the current to be as bright.

The part number is 276-026. I notice three other differences between this and my other red LED's. The epoxy case is tinted a lighter red, the case is a bit longer, and the peak wavelength is 700 nm.

This part number is shown on RS web site but the description of the LED on the web site is different from what's on the package.

Anyone know of another source for a LED like this? Anyone know if such an efficient LED is available in other colors?

What is the forward voltage of the LED you are using ?

I have one handy here in my fan speed controller.

It's drawing a whopping 0.66 ma and the forward voltage is 1.82 volts.

By the way, this isn't just an onboard indicator, it's visible on the front of my computer to indicate the fan/temperature status, and is easily seen day or night.

I love these LEDs.

I'm pretty sure that I know which one you're talking about. I've had it in their assortment so I've never had any specs on it.

I think the reason that it is so visible is that it behaves like it has no viewing angle. It's almost like it's frosted and acts like a bulb, so you can see it from any angle and light has less effect on it. I've seen a similar one in 5mm.

The only Radio Shack red LED like this I've come across came in their 20-LED assortment package. The entry for it I have on my website is:

This is an unusual looking LED, packaged up in a custom case. The case, which is transparent but tinted a deep ruby red, has an inverse conical lens - that is to say it is deeply concave and cut in towards the LED chip in the center, rather than being rounded like a regular LED.

When lit, this LED produces a small spot of a deep red color and has a very wide beam of approximately 100 degrees. It was apparently designed to be visible off to the sides to the same degree that it is visible head-on. The only problem is, it's not very bright at all. Spectrographically, it shows a fairly wide range of colors from deep red all the way into yellow; but most of its energy comes from the red region.

This LED came in a package offered by Radio Shack, which consisted of about 20 mixed, unsorted LEDs of all types and colors. So its origin is unknown, and its intended use is also unknown - I haven't seen an LED of this type in service anywhere in the last twenty years; other than the ones I've ended up with and either lost or installed in hobby equipment. Anybody who's bought Radio Shack's 20 ct. LED grab bag has probably ended up with a few of these.

The one I tested was installed in a toy many years ago; when the toy broke, I cannibalized it for its electronic parts plus the LED I put in it myself. So this LED has just been clunking around in the bottom of a toolbox for who knows how many years before I put this webpage up.

These are current R.S. stock. They come two to a package for 99 cents. They look like all the other 3 mm leds I have. It seems my 3 mm leds are in two different lengths with the longer ones being 1 mm longer than the shorter ones. These are in the longer category. Actually these seem to have a slightly larger diameter too. About one or two hairs width, whatever that is in "SI".

I too suspect the optics is part of it.

The tint of the case is a lighter red than my other reds, almost pink.

The intensity doesn't fall off much from dead center to 30 degrees. Still pretty good at 60 degrees.

Anyway these are all I use now. I'm tired of trying to figure out how much current to pass thru a yellow or green to make it easily visible. I know when I use one of these, it will be okay.

I've come up with a new color coding standard. Red means good, red means bad, and red means indifferent.

The down side is I have to visit my local R.S. every couple of weeks and clean out their entire stock of one package.

Yeah, I know I could order on-line, but I was hoping one of you would have another source.

I guess I'll go to my Radio Shack tomorrow and see if they have these LEDs then. I guess in this case the only way to know for sure is to buy & try yourself. /ubbthreads/images/graemlins/grin.gif

(Edit, a moment later)
According to the website, this LED is not available at the downtown Seattle Rat Shack. /ubbthreads/images/graemlins/frown.gif

I really like your color coding system.

Telephony, I can mail you some but it will probably be a few weeks. I am using up my stock today. As I cleaned out the local Radio Shack a week ago, they are probably out too.

I don't want to order on the web now because I will be out of town when it is delivered.

I would say you'd be better off just looking for a diffuse packaged LED from a more standard source. My experience with these indicates that what you're really liking about them is the fact that they're visible from all angles (which is mainly due to the diffuse packaging). Try sanding the outside of a more standard LED lightly with a fine grit sandpaper to see if it has a similar effect for you.

[ QUOTE ]
eluminator said:
Telephony, I can mail you some but it will probably be a few weeks. I am using up my stock today. As I cleaned out the local Radio Shack a week ago, they are probably out too.

[/ QUOTE ]
Thank you for your offer! I'll check my local Rat Shack in person today, in case that web page is incorrect. It'll probably be in the 1:00pm hour, and I should be back home and post my findings here sometime in the 2:00pm hour. By then I'll know if you need to mail some to me or not.

I just got back home, and sure enough, my Rat Shack is out of these. After I asked about a custom shipment, one of the salesmen said the LEDs (all of them) would be resupplied in a week, so I'll check again then.

Eluminator, I don't think you'll need to mail me any, but we'll see in a week when I go back there and see if they have these LEDs in stock.

Running from (creaky) memory, I remember that there was a series of LEDs awhile back that were optimized for use at 2ma or less, for direct driving from digital circuits. Supposed to be brighter at way less current then standard LEDs of the time. Something that may be less of an issue nowadays.

Enjoy, yours, drs the crazed.

You're quite correct.
Radio Shack used to sell "low current" LEDs, diffused red I think, that were purposefully designed to use 2mA or less.

[ QUOTE ]
TheFire said:
Try sanding the outside of a more standard LED lightly with a fine grit sandpaper to see if it has a similar effect for you.

[/ QUOTE ]
i cheat.
i stick the led into a port of my sparkplug sandblaster.
takes a few seconds and you have to keep turning it to get it even.

[ QUOTE ]
Telephony said:
You're quite correct.
Radio Shack used to sell "low current" LEDs, diffused red I think, that were purposefully designed to use 2mA or less.

[/ QUOTE ]
I remember purchasing one of these at RS for a project. I think it's floating around in my basement somewhere. Do you need one?

Ok, it's been a week and Radio Shack was still out of 276-026 3mm diffused reds, so I special-ordered a pack to be delivered right to me in about 5 more days.

OK, it was not five days...it was seven. But I now have a package of two 276-026 3mm red diffused LEDs.
According to the back of the package, this LED has the following specs:

Power dissipation: 45mW
Forward current: 15mA

Optoelectric characteristics (at 20mA)

Forward voltage: 3.0V
Luminous intensity: 2.5mcd
Peak wavelength: 700nm

Ehhh doodlebugs!!! Now I done forgot what I was supposed to do with these LEDs. Guess I'll do a short writeup of them and put it on my red LEDs page. /ubbthreads/images/graemlins/blush.gif

(Edit)
It's now on my red LED page right here if anyone's interested.