commgrp@silver.bacs.indiana.edu (12/22/88)
I've had my share of woes with Radio Shack products but this time they
have a winner!
RS catalog # 276-087 "Super-Bright LED" ($1.69, from Japan) is truly
impressive. It's rated 2000 mcd output at 20mA (red; wavelength 660
nm).
My friend John Halleck says that it's more robust than similar LEDs
made by Panasonic and sold by Digi-Key, and can take 70mA continuous
current (see below).
At 40mA the direct main beam is too bright to look at comfortably, and
leaves an afterimage. It projects a visible spot on a white wall five
feet away in normal room light.
This LED with series resistor, plugged into Mini-Mag (tm) flashlight
(two AA-cells) makes a long-duration emergency light. (Pilots and
sailors take note.) I plan to use one to illuminate an automobile
instrument. Maybe I'll use one with LM3909 to fake a car burglar-
alarm.
It's a far cry from the first LED I ever saw, circa 1966! A Hewlett-
Packard salesman demonstrated one mounted in a velvet-lined jewelry
box made to hold a ring. It was gold-plated and beautiful, though
barely visible, and cost $70.
Excerpts from e-mail from John Halleck (nahaj@cc.utah.edu):
They are a little more robust in the face of overvoltage than the
Panasonic ones. (Yes, I am surprised they are not the ones I thought
they were.) They are as bright.
My backup cave light is nine of them (70ma) at 6 volts (4 AA's).
Really bright! (Grouped as 3 paralleled groups of 3 in series in
series with a 10-ohm resistor. The resistor is only needed to limit
current with new batteries; after an hour or so you can switch it out)
The resistor may be omitted if you don't mind running at or slightly
above the max rating when the batteries are new.
The 3 x 3 array makes one HELL of a bike tail light. It's painful to
look into at 10 feet.
> Do you leave the leads long for heat sink?
No, I mount them on a perf board, and clip the leads short. (Zero
heat sinking.)
The RS LEDs have a number of differences from the Panasonic
equivalents that I've tried.
The voltage drop is higher.
The tolerance to over-current is MUCH higher. 30mA is the published
Absolute Maximum; I have run them up to 175mA for 30 seconds. At this
level, they are very bright but they are permanently damaged. After
the damage they have a higher internal resistance, but still
functioned. This same test totally fried the Panasonic LEDs; the RS
ones survived. RS LEDs were warm but not hot at the end of the test.
After the test, I compared them with non-abused ones. The light
output was down (visually) about 50 %. Current was reduced for any
given voltage.
I cannot get any information as to their lifetime.
They are FANTASTIC hooked to a LM3909 and flashing. In a dark
room they will put a visible spot on a wall 20 feet away.
No idea of the manufacturer or type number. It does not seem to be
any of Panasonics.
Update: The damaged LED's were put back in service. (I am doing
battery and LED lifetime tests. The damaged ones were (visually) 50%
down compaired to the non-abused ones when put back in service. They
were
a LOT less than 50% of the brightness after another 24 hours, and one
of the three has now failed totally. Walt Howard from our local EE
dept theorizes that there was less active area after the abuse,
causing the current density in the remaining area to skyrocket when
the original 20ma was restored.
-Nahaj
--
--
Frank Reid W9MKV
reid@gold.bacs.indiana.edu
Radio Shack's mailing list - Just say no!flaig@Apple.COM (Charles Flaig) (12/23/88)
In article <7200022@silver> commgrp@silver.bacs.indiana.edu writes: >RS catalog # 276-087 "Super-Bright LED" ($1.69, from Japan) is truly >impressive. It's rated 2000 mcd output at 20mA (red; wavelength 660 >nm). Of course, the *REAL* question is: How do they perform when immersed in liquid nitrogen? Original LEDs had a significant increase in efficiency when supercooled. Coupled with the increased power handling capability, it's possible to get a surprising amount of light out of them (at several hundred mA). I had fun playing with this in college. Unfortunately, the high efficiency LEDs (40mcd) I tried didn't have the same effect. It would be interesting to know if these new LEDs do. They would be really impressive with several hundred mA of current at significantly higher efficiency! --Charles flaig@apple.com
cook@stout.ucar.edu (Forrest Cook) (12/23/88)
In article <7200022@silver> commgrp@silver.bacs.indiana.edu writes: >RS catalog # 276-087 "Super-Bright LED" ($1.69, from Japan) is truly >impressive. A local store (J.B. Saunders) has Hewlett Packard high intensity LEDs for $0.20 ea, quantity 1. They are very bright and open up such uses as high speed communications over light beams. This is not really a new application, but one which can be improved upon with the new LEDs. ^ Forrest Cook (The preceding comments were my Opinions) ^ /|\ cook@stout.ucar.edu /|\ /|\ {husc6 | rutgers | ames | gatech}!ncar!stout!cook /|\ /|\ {uunet | ucbvax | allegra | cbosgd}!nbires!ncar!stout!cook /|\
jbn@glacier.STANFORD.EDU (John B. Nagle) (12/23/88)
HP has been selling LEDs like this for about a year, but they aren't a well known part yet. HP was targeting the automotive taillight market, and the lifetime taillight has already been seen on a GM experimental vehicle. With the need for lamp replacement eliminated, the lamp assemblies can be made more compact and integrated better into the body parts. John Nagle
commgrp@silver.bacs.indiana.edu (12/29/88)
Further excerpts from e-mail correspondence about super-bright LEDs:
To: reid@gold.bacs.indiana.edu
From: "John Halleck, Postmaster" <NAHAJ@miriam.utah.edu>
Somebody... claimed that HP had high-brightness LED's for
only 20 cents or so. I called HP and asked.
They deny the rumor... although I was not the first one to ask.
The information below comes from their salesman [name deleted].
The only basis in fact of the rumor is that the HLMP4101 is a 1000mcd
LED and has been around as long as the rumor. They are $1.10 in
quantity of one. Brighter ones are not currently availiable, but they
claim that they will have a new line of them in June. The sizes in
June will be 2000mcd, 3000mcd, 5000mcd, 8000mcd (!), and (!!!)
12000mcd (!!!!). The prices for the 2000 and 3000 look to be about
$2.00 each in quantity one.
I talked to six people at HP, and unless the part number is SO obscure
that the sales staff (here and in Colorado) has never heard of them,
and can't get the number, or ... The fellow did not know what he was
talking about.
-John Halleck
--
Frank W9MKV
reid@gold.bacs.indiana.educook@stout.ucar.edu (Forrest Cook) (12/31/88)
In article <7200025@silver> commgrp@silver.bacs.indiana.edu writes: >Somebody... claimed that HP had high-brightness LED's for >only 20 cents or so. I called HP and asked. They deny the rumor. >The fellow did not know what he was talking about. J.B. Saunders Co. (303) 442-1212 sells what they claim to be high intensity LEDs for $0.20 ea. They may not be the same as the HP 1000 mcd units but they are bright. These devices come in a clear package and have a tiny red dot on the side but there is no indication of the manufacturer. I have no affiliation with J.B. Saunders other than being a satisfied customer. ^ Forrest Cook (The preceding comments were my Opinions) ^ /|\ cook@stout.ucar.edu /|\ /|\ {husc6 | rutgers | ames | gatech}!ncar!stout!cook /|\ /|\ {uunet | ucbvax | allegra | cbosgd}!nbires!ncar!stout!cook /|\
jpexg@hermes.ai.mit.edu (John Purbrick) (01/03/89)
The original article was about powerful visible LEDs, rated in candelas, which is normal for visible light. How does this compare to infrared LEDs, which are usually rated in terms of total watts and watts/sterradian (watts radiated into a unit angle at the brightest point)? Are the visible lamps catching up to the IR ones? Note: Visible light, measured in candelas, is nonlinearly related to actual power, because the candela takes into account the varying response of the eye to different colors. An infrared lamp rates 0 candelas, although most Hewlett- Packard IR LEDs seem to be near-infrared and emit a small amount of visible light too. "Aids alignment", as the catalog says.
A-N-Onymouse@cup.portal.com (John - DeBert) (01/23/89)
Radio Shack has another hi-brightness LED, the SLA-591LT3 (276-066A)
rated @ 500mcd, 20ma, Pd 100mW, 660nm. Price is $1.19 ea.
Also, they have super-bright yellow LED's, #276-054, t1 sized, 2.2v, 10ma.
These seem much brighter than the others. Price is 2@$0.69.
I've used the former for nightlights, darkroom lighting and indicators on
my bike. They are much more noticable at night that are the stock lights.
A bank of ten (soon to be twenty) of the latter LED's light up my
workstation and radio listening position. They also fit the mini-Mag-Light
when the ridge is shaved off, making a nice, virtually unbreakable flash-
light.
A.N. Onymouse
A-N-Onymouse@cup.portal.com
Telex:6502636614 | CIS:75530,347 | GEnie:A.N.Onymouse
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