Is a red LED just a red LED?

I'm on the hunt for a single cell red LED now, and have been eyeing up Gerber Infinitys and even the Recon, until I saw how small the actual output is with the filters in place. That would be the perfect light for this use, if not for that.
I recently decided to try my hand again on 2 simple mods, which I never would have been able to do without discovering this fourm. I swapped the LEDs from a Dorcy AAA and an Arc clone with 2 red LEDs from 2 Spiderman wrist light toys that ran on 2 coincells.
The Arc clone ran for a day but isn't working now, but the Dorcy is going well, was SO much easier than that clone to fuss with.
Is this a good solution for me, or is it really worth dropping the $15-$30 on a Gerber or Peak?
Also, are there different grades of red LEDs? Should I get a specificly bright one for the Dorcy mod?

I'm only interested in a red light, because I don't have one. That's really it. I don't have any specific appilcations or need for one.

I'm not 100% sure what you are asking, but just to throw out there, typically red, orange, yellow and amber LEDs have a much lower Vf or forward voltage than white, blue and green LEDs. In some instances, if the light is sending maybe 50ma at 3.7V to a white LED that is spec'd at 20ma at 3.7V and you replace it with a red LED that is spec'd at 20ma at 2.2V, it may fry instantly or it may work for a day or so then die or it may work indefinately... Either way, you are abusing it.

I've found that you can run a 20ma white, blue or green LED just fine directly off of 2 alkaline cells, but if you try a 20ma red LED directly off the same alkaline cells, it will pretty much die instantly.

For now, the long term red LED mod I've done is a 100ma LED from LSDiodes.com in the Inova X1... but the X1 only sends about 20ma to the LED so while it is being overdriven voltage-wise, it's being under driven current-wise. I've run it through three alkaline cells, the first two were with intermittant use, the last one was continuous and it still seems as bright as when I first built it.

Bottom line is, I'd tend to think that if you have an LED light that doesn't significantly overdrive the white LED much, a red LED swap may work out fine. If you have a light that sends 60 or so ma to the white LED, it will probably kill most red LEDs pretty quickly.

cratz2 said:

Bottom line is, I'd tend to think that if you have an LED light that doesn't significantly overdrive the white LED much, a red LED swap may work out fine. If you have a light that sends 60 or so ma to the white LED, it will probably kill most red LEDs pretty quickly.

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Well then, I very well could have fried the Arc clone's red. I figured a red would be ok in the Drocy since it has a resistor, and either way, in the end these were just LED pulled from toys, and I'm not worried if they fry. I could get a specific voltage red LED for the Dorcy if it's advisable.
Or just get a Peak/Gerber, if they'd be brighter. I'm having no luck with finding output numbers with red LEDS, besides the few that Quickbeam has.

And in all honesty, I'm not sure how comparable the numbers are comparing a red light to a white light. I mean, a red 4 lumen light probably isn't nearly as bright to our eyes as a white 4 lumen light. Seems like most folks use red lights either to preserve night vision or for extended battery runtimes - again, since they have a lower Vf, they will last longer on a single cell.

What exactly are you building the light for? Or is it just for something different to play with?

Just something different, Cratz. I won't be comparing it to anything, and I know a red won't be anything like a white LED. I'm trying to round out my collection, in a way. Currently I don't have any red lights, besides a waterproof light that runs on large coincells, and an old EB Micro Lenser. I just wanted a lower end one because I simply do not have one yet. I've got the Dorcy now, but I wasn't sure how it'd hold up, and if buying a Infinity or Peak would be better than wasting time and solder.
I figure, if I see any come through BST in my price range, $15-$25, I'll give it consideration. Until then I can play with the Dorcy and see if it lasts.

Also, if anyone with a Gerber Recon could chime in, I would seriously love to know if the red filtered light holds up to a red LED light like a Gerber/Peak. The Recon is great because of the different color options, I'm just wary from some reviews saying the red/blue/green filters cut the output down alot. I figure a red Infinity will be much brighter than the Recon's filtered red. But again, I can't find any direct comparisons.

cratz2 said:

And in all honesty, I'm not sure how comparable the numbers are comparing a red light to a white light. I mean, a red 4 lumen light probably isn't nearly as bright to our eyes as a white 4 lumen light.

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Yes it is. Lumen is a measurement which involves the response of our visual system.

cratz2 said:

And in all honesty, I'm not sure how comparable the numbers are comparing a red light to a white light. I mean, a red 4 lumen light probably isn't nearly as bright to our eyes as a white 4 lumen light...

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Well said. If you click on the imagelink below a color sensitivity chart will come up. It's kinda crude but it does reinforce the point that the human eye doesn't utilize the red part of the spectrum well.

The red lights usually recommended for retaining dark adaptation are usually in the ~625-630nm range, which the rods can actually still see. A red light which is truly above rod sensitivity (~640nm) would even be harder yet to work with.

I have a few lights in the ~625-630nm range that I've experimented with a bit -- but thats about all I do with them. I'd like to try out a light at ~640 -- because I'm curious.

The Gerber Recon I have measures 9,600mcd with no filters in place (emitting white light) and 700mcd with the red filter in place.
I would expect to see no less than 5,000mcd from a red-emitting LED (~625nm-640nm) that was made to be a red LED.

Wim Hertog said:

Yes it is. Lumen is a measurement which involves the response of our visual system.

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Really? That goes against everything I've ever known about physics. I mean, I've only been into modding flashlights for a couple years and I have no integrating sphere... heck, I don't even have a light meter. But to paraphrase Forest Gump, 'I know what bright is' and anytime I've ever compared two lights of the same design (such as a white Infinity Ultra and a red Infinity Ultra) the red seems MUCH dimmer to my eyes.

I know this is a very crude method of comparison, but my general point is, I think that if someone has a 5 lumen white light and they want a 5 lumen red light, that running an LED of similar design on similar current but less voltage (as intended) might leave the modder a bit disappointed.

Honestly though, I have no idea...

The_LED_Museum said:

The Gerber Recon I have measures 9,600mcd with no filters in place (emitting white light) and 700mcd with the red filter in place.
I would expect to see no less than 5,000mcd from a red-emitting LED (~625nm-640nm) that was made to be a red LED.

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Craig, I forgot to check your site for comparisons!
Thanks for the post, I am figuring a red LED light would be alot more brighter than the Recon's red.

Omega Man said:

Craig, I forgot to check your site for comparisons!
Thanks for the post, I am figuring a red LED light would be alot more brighter than the Recon's red.

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Hey don't worry about it.
Red LEDs that were born as red LEDs will always appear significantly brighter than a white LED filtered to be red - assuming input power (in watts) is similar.

Hi Omega -

I've had a practical interest in red LED's lately. From what I've seen, filtering out all but red light from white LED's is a poor way to go because they mostly lean toward the bluer end of the spectrum and just don't contain a great deal of red wavelength light in the first place - and of course a filter is only a way to eliminate part of the spectrum, waste it as it were.

It's a little bit out of your stated budget range, but two red LED assemblies I really like are:
(1) Inova 24/7. This was a bit of a surprise to me, but the two red LED's put out a wide cone of light, supposedly good for 80 hours, very very uniform illumination, plenty bright for indoor navigation and close to medium tasks. Plus all the other neat things it does....
(2) TLE-5 drop-in for MiniMag. This puts out (to my eyes at least) an abundant amount of light for outdoor navigation, uses cheap batteries. I like it best with a glass diffusing lens and tailcap clickie.

Good luck!

- Bill

woodfluter said:

(1) Inova 24/7. This was a bit of a surprise to me, but the two red LED's put out a wide cone of light, supposedly good for 80 hours, very very uniform illumination, plenty bright for indoor navigation and close to medium tasks. Plus all the other neat things it does....
(2) TLE-5 drop-in for MiniMag. This puts out (to my eyes at least) an abundant amount of light for outdoor navigation, uses cheap batteries. I like it best with a glass diffusing lens and tailcap clickie.

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Thanks for adding, Wood. I've seen the 24/7 also and think it's neat, but I was looking for single AA or even AAA light.
As for a TLE5, are you using a red filter overtop of it?
Or do you have a red mag dropin?

Well now that I've got a red CMG sailing my way, I'll be able to answer this on my own. Thanks for the replies.

Shine it at something red and then see what it really can do!!

there is tle-5 availible in all the luxeons colours . go to: http://www.flashlightreviews.com/index1.html

it shows the full set and how it rates

There we go, thanks for the link Chester. Now I know what Wood was talking about. They look sweet, it'd be good to have such bright colors from those. May need one if the CMG gets me fired up about colored leds.

For what it's worth, here's an easy way to determine if a particular red light is within the color spectrum for preserving night vision.

Several years ago I was in an electronics surplus store and came across some cheap 2-AA red LED flashlights that I presume had been a promotional product put out by Hewlett-Packard. On one side of the case it said "AlGaAs LED Technology", the other had the HP logo. I bought a handful and gave one to my brother-in-law, who happens to be into Astronomy.

He wondered if the red LED could be used to preserve night vision. He said he had an easy way to tell. Shine the red light in question at the red and white "Sky and Telescope" logo/title on the cover of that magazine (you need to do this in the dark of course). If you don't see the letters (the title area appears white), then the light is producing the correct spectrum of red to preserve night vision. It turns out that these HP LEDs did just that.

I don't know where he learned about this technique or whether it is actually accurate, but it seems plausible.

Thartley :I noticed that when I was reading a far side gallery book. I was reading with a red LED light and came across a strip that I could have sworn had writing on it. Sure enough when I switched to white, the writing stood out instantely.

Omega Man said:

As for a TLE5, are you using a red filter overtop of it?
Or do you have a red mag dropin?

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It is a red TLE-5. A red filter on the white TLE-5 (I have one) is pitiful - the red LED is quite a decent amount of light.