LED specs for panel indicators?

[stoneattic]

As some of the folks here who have helped me know, I'm in the process of replacing a few burned out LEDs in a couple of rack mounted power amps.

There are a TON of options for Luminous Intensity, Viewing Angle, etc. I've changed plenty of stompbox LEDs or changed the current limiting resistor to get them brighter. I never use batteries so I'm not worried about the additional draw. Of course at first I tried the ridiculous ultra-brights with really tight viewing angles that burn your retina out, but later changed them to more reasonable brightness LEDs.

So in this case I'm looking for something similar to what was in there, but of course I don't know what they were. Neither manufacture stocks them or were able to give me any info on them.

A couple of twists are that one of the amps uses lenses like these:

8671 Keystone Electronics | Mouser



and the other uses 5mmx2mm rectangular LEDs that are more of less flush with the front of the panel.



Also, there are green, red and yellow LEDs, which makes we wonder if the different colors appear to have the same brightness at different intensities and angles. It seem like the LED manufacturers don't have matched color sets, or at least not that I've been able to find.

I'd be interested in hearing what folks are using for similar applications.

Thanks!

[Enzo]

We are looking at generic commodity LEDs here. If you want specially color coordinated sets of LEDs, I imagine you could pay someone for them. To be honest, I suspect you are putting more time and energy into LED selection than the circuit designers.

If it were in front of me, I'd use generic LEDs from Digikey or Jameco or someplace. If they were special, Samson or whoever would stock them. Heck, even Radio Shack probably had a selection pack of LEDs that would work.

LEDs will always have a current limit resistor unless you buy "indicator" assemblies, which is a mountable package with LED and resistor inside. If you are concerned with one LED seeming to be brighter than another, you could mount little trimmer pots to adjust the current limiting resistance.

[stoneattic]

No doubt I'm over thinking it, like I do with everything else. In the pre-internet days I would have just grabbed whatever Radio Shack had, which if I remember correctly, were 2 red and 2 green, in "standard" and "low current" models.

But now with the all the choices it's very confusing. If you search Mouser for stocked red, T-1s you get 185 choices! So even generic, LEDs give tons of options. Even if I narrow it down to diffused, etc, there are still a bunch of choices regarding intensity and viewing angle.

I don't know if matched sets was what I really meant, but I was assuming that they would have "series" of LEDs with similar intensities and viewing angles that kind of went together, like the 2 types that Radio Shack stocked in the old days.

I've read that 50mcd is a "common" choice for indicators, so I guess I'll just grab something in that range with a wide viewing angle. Athough I'm not sure if the viewing angle means much with the lenses or flush mounting.

My wah has super brights with a small angle coming out of the sides so I can see them easily with my big foot in the way, but they looks like blue light sabers. Kind of cool, but if you accidentally look at it directly you're blind for the next 30 seconds! I had a super bright in my modded DS-1 but I couldn't look down at to tweak the knobs without covering the LED with my hand. I was able to tame it with an appropriate limiting resistor, but the point is I want to easily see when these are lit without being blinded.

I was even trying to find part lists for various power amp or other devices with similar set ups to see what manufacturers where using but haven't had any luck with cross reference-able part numbers or specs.

[Enzo]

So there are 185 choices. Stocked T1 red, diffuse, OK so far. Round/flat/other? Mounting should weed out a few, I assume you want radial leads, not axial or surface mount. Some LEDs come with molded on right angle blocks, others have pre-bent leads, each will have a different part number. (Ever see small transistors with all three legs in a row, I am sure you have, now ever seen the same type in something but the legs are in a triangle arrangement, and the wire legs are prebent to shape? That is an available option. LEDs have similar options) Now for any particular choice, there will be bulk, or on tape, or "ammo box." That refers to how the parts are stored. So it may be three options,. but all the same part. I like them loose, but taped is fine too, I just snip them off the strip as I need them. If Mouser sells LEDs from 10 different brands, well then there will be 10 sets of size shape packaging etc for each one.

years ago I got my first digital meter. It was a time when most guys had analog meters. They'd look at my meter touched to a battery and it said something like 1.516v, with the last digit wandering a little. "All those NUMBERs" they wail. I said, you want less numbers? Put tape over the last couple, then it will look like a nice steady 1.5v. Ignore the excess. I offer the same advice, so you have a ton of choices, just find one that works, it doesn;t matter in the slightest if there are 15 more that would work just as well. If the prices are a couple cents off, who cares, you aren;t ordering 10,000 are you? And when you see a 9 cent LED and one next to it that is $3.95, then ignore the $4 LED. ANything special about it has nothing to do with your needs. SOme parts are milspec, some have some really esoteric aspect like the flat side is every so slightly narrow or the diffusion dome is flattened a little or god knows what that some OEM specified or some govermental requirement covers it because it is the power on light in an air traffic control console.

[stoneattic]

I like the analogy.

The 185 is taking into account radial leads, no right angle blocks, or pre-bent leads:

Standard LEDs - Through Hole | Mouser

The package like you described doesn't matter, especially since I would only order a few of each. Like you said, I'm not ordering 10,000. I don't care who the manufacturer is, or Wavelength/Color Temp. So let's go with a "typical" forward current (20mA) and "typical" Forward Voltage (1.7-2.1). I'm still at 64. Searching for "diffused" leaves me with 34.

My big questions are what is a good Luminous Intensity and Viewing Angle.

Of the 34 still left the Luminous Intensity ranges from 1.5 to 1,300 mcd and the Viewing Angle ranges from 16 to 90 deg. Both pretty wide ranges.

Like you said, I'm over thinking it, assuming there is a "perfect" choice for the application.

[Mick Bailey]

I bet these are the cheapest the manufacturer could get hold of. Cheapest is the best replacement with consumer equipment LEDs. If necessary, adjust the limiting resistor to match brightness.

[Enzo]

Unless I have some particular special use, I just look for cheap and generic, as I am sure Samson did.

I just Mousered LED, through hole, red, 2x5mm and have 9 choices.

Viewing angle is 110 to 140 degrees, so not an issue.
They are all 2v forward, but if they were 2.2 or 1.8 it wouldn't matter, so they'd be a tiny bit brighter or dimmer.
All are 600 and some nm wavelength, so they are all red of some sort.


Mouser has a million things, maybe you'd prefer the selection at Jameco, they are set up more for the hobbyist.

[bob p]

When it comes to luminous intensity I think that lower is better. I really don't like having bright LED lights on audio equipment. It's not like you're going to put your gear in direct sunlight, where you'd need a lot of luminous intensity for the LED to be seen. House lighting typically isn't all that bright, so luminous intensity needs are minimal. If you stick with lower levels of light, you have a useful indicator. With too high a light level you get a beacon that becomes distracting in a dimmed room, and a bright LED makes it difficult to read an instrument's front panel.

IMO lower luminous intensity is good, wide diffusion angle is good, but in reality, with stereo gear wide angle isn't all that important because it's uncommon for someone to try to read a stereo panel from the side.

On a personal note, I hate blue LEDs and white LEDs. My retinas find them quite annoying to look at.

[Mick Bailey]

In the 1980s I was the first customer to buy a particular model of high-speed printer from Fujitsu, but there were teething troubles with it. So, Fujitsu sent an engineer from Japan to take a look as it was such an expensive piece of equipment. The thing I remember about this was he couldn't wait to tell me about something he'd seen in the lab - a blue LED. He kept coming back to it - "a blue LED - you know what that means?"

Have to say it was a good few years afterwards before I saw them for sale.

Now they're in every piece of crap. I don't like them either. Kids drive around with them all over their cars in England.