Cree XP-E 'Far Red' 730nm wavelength emitters

goshdogit · 2018-07-30T00:45:53.000Z

There’s a recent post on r/flashlight about ‘far red’ light. It includes a (desaturated) video made with a camera without an IR filter. The poster is using a “3 watt 730nm LED from eBay.”

I enjoy looking at objects lit by UV (with protection! :sunglasses: ) but hadn’t heard of playing with light at the other extreme of the visible spectrum!

Searching for 730nm emitters revealed Cree’s XP-E ‘Far Red’ variant. It seems there’s no XP-E2 replacement yet.

Digi-Key sells singles, and they’re in stock. It appears they’re the ‘group 11’ bin.

Here are a few specs lifted from Cree’s datasheet.

LEDsupply sells loaded single and triple MCPCBs.

Does anyone have experience with far red? Is it fun, like UV? :partying_face:

DavidEF · 2018-07-30T00:55:41.000Z

So, what kind of fun is to be had with Far Red light? What cool things can be seen, or seen differently?

AgentWhiteBread · 2018-07-30T01:06:24.000Z

In the video he was able to see black text written in sharpie on black cloth because the cloth showed as white while the sharpie was still black. You could send secret messages? Idk.

Cereal_killer · 2018-07-30T01:22:17.000Z

AgentWhiteBread:

You could send secret messages? Idk.

Dude you gotta edit the title of the post man. Lead with the good stuff, this is gold bro! Say no more

I need a far red light like yesterday, gotta get my spy on.

AgentWhiteBread · 2018-07-30T03:08:24.000Z

Right? On the /flashlight post I said I have the 670nm H502pr Zebralight headlamp unfortunately it’s not “far red” enough for the effect to work so I said if Zebralight is listening I would totally buy an H602fr/H502fr with the far red emitter so I can get my spy on.

staticx57 · 2018-07-30T03:28:04.000Z

I have a few of these. Even put one in a Lumintop Worm, but had no idea what to do with it till now.

eBay

10 pieces OSRAM OSLON SSL 80 COLOR LED Far-Red 730nm GF CS8PM1.24...

Find many great new & used options and get the best deals for 10 pieces OSRAM OSLON SSL 80 COLOR LED Far-Red 730nm GF CS8PM1.24 Horticultural at the best online prices at eBay! Free shipping for many products!

travis · 2018-07-30T03:36:03.000Z

Is this wavelength safe to view with the naked eye; no filtering goggles needed?

Cereal_killer · 2018-07-30T10:33:28.000Z

staticx57:

I have a few of these. Even put one in a Lumintop Worm, but had no idea what to do with it till now.

10 pieces OSRAM OSLON SSL 80 COLOR LED Far-Red 730nm GF CS8PM1.24 Horticultural | eBay

Did you buy them from that link? Just curious.
I have some red osram oslons but I got them from some LED tail lights I disassembled so I have no idea on their specific wavelength / bin

maukka · 2018-07-30T11:56:18.000Z

travis:

Is this wavelength safe to view with the naked eye; no filtering goggles needed?

Incandescent light bulbs have a lot of far red and IR. So unless this is mostly invisible so that the pupil doesn’t contract or the intensity is very high, I don’t think it’s a problem. I would think 720-750nm is very visible still. So probably no need to wear any glasses unless you’re viewing it directly or in a pitch black room.

djozz · 2018-07-30T12:09:09.000Z

At least the ‘green’ cone in the human eye has no sensitivity for light longer than 650-700nm, so anything higher than 700nm will just be recorded by the red cone and will appear the same dark red colour. Also from 700nm on your eyes become highly insensitive so you need enormous power to get a decent visible illumination. I think anything higher than 720nm will appear pretty invisible.

Lux-Perpetua · 2018-07-30T12:12:47.000Z

I assume those XP-E Photo Red are more useful than Far Red, right? There are a lot of controverse discussions whether or not deep red light (> 650nm) is better for maintaining one’s night vision ability compared to normal red light with 625-650nm (= XP-E2 red).

maukka · 2018-07-30T12:23:10.000Z

djozz:

I think anything higher than 720nm will appear pretty invisible.

The OP in the reddit thread said

I have some 730nm LEDs, and I built a flashlight from a 3 watt one. When I take this light into a room and shine it on my black fabrics, the fabrics shine back red. Even more interesting is the fact that if the black fabric had been written on with black permanent marker, the writing becomes readable. Far-red LEDs make any other red LED look a bit orange by comparision

At least he sees them as red. Of course we don’t know if the ebay LEDs are actually 730nm. I wonder who would have equipment to verify those…

djozz · 2018-07-30T12:35:16.000Z

As long as the intensity is high enough you will see it (there is some sensitivity up to 800nm, probably a bit different for each individual) , it is a very inefficient way of illumination though, you need hundreds of times more radiation power to see the same intensity as green light.

goshdogit · 2018-07-30T14:07:51.000Z

Thanks for all the input. Perhaps I’m overestimating the novelty of far red to the naked eye. I was hoping to be wowed. :laughing:

Does it create any interesting visual effects aside from making some black materials appear red? Is it only impressive in conjunction with a camera?

My friend has a modified DSLR with the IR/UV filters removed, so far red would be fun with that.

emarkd · 2018-07-30T14:13:53.000Z

FlashTom:

I assume those XP-E Photo Red are more useful than Far Red, right? There are a lot of controverse discussions whether or not deep red light (> 650nm) is better for maintaining one’s night vision ability compared to normal red light with 625-650nm (= XP-E2 red).

I’ve built lights using XP-E 660nm “photo red” emitters, and XQ-E 670nm emitters. Both are more pleasing to my eye than normal 630nm red. In fact I don’t care for the 630s much at all since trying the higher wavelength stuff. They do indeed look quite orange in comparison. Whether they’re actually more useful or not, I can’t say. But I do like them quite a bit better.

I’ll have to order up some “far red” stuff to play with.

goshdogit · 2018-07-30T15:51:02.000Z

emarkd:

I’ll have to order up some “far red” stuff to play with.

I saw you in the reddit post and was hoping you’d chime in here. :+1:

I’d like to try a far red triple. I have a spare copper spacer, some Carclos, and an empty S2+. It’s even red.

I thought I’d either reflow some bare emitters onto a Noctigon triple, or use this triple from LEDsupply rewired for parallel:

The loaded board from LEDsupply is $12 with free shipping. Three bare emitters from Digi-Key would be about $9 with shipping.

I don’t have any experience with limiting a driver’s output. Maybe I could tweak Bistro’s code to limit the power of an MTN FET + 7135 driver? I already have a couple and would rather not fiddle with ordering components to build or modify a driver.

What are your build plans?

djozz · 2018-07-30T15:58:24.000Z

You want different hardware, not soffware. A 7135 current controlled driver would work for these (such as a 3A biscotti driver from Simon, so for 1A per led). And hope for the best because a lot of overvoltage needs burning off by the driver A lower voltage battery like a LiFePo battery could help with that.

DavidEF · 2018-07-30T19:17:52.000Z

djozz:

You want different hardware, not soffware. A 7135 current controlled driver would work for these (such as a 3A biscotti driver from Simon, so for 1A per led). And hope for the best because a lot of overvoltage needs burning off by the driver A lower voltage battery like a LiFePo battery could help with that.

Or maybe a buck driver because the Vf is low enough to make use of the conversion?

djozz · 2018-07-30T19:27:23.000Z

DavidEF:

djozz:

You want different hardware, not soffware. A 7135 current controlled driver would work for these (such as a 3A biscotti driver from Simon, so for 1A per led). And hope for the best because a lot of overvoltage needs burning off by the driver A lower voltage battery like a LiFePo battery could help with that.

Or maybe a buck driver because the Vf is low enough to make use of the conversion?

I assume that would be better even, you need more than half a Volt overhead and this is almost 2V so it should be fine , but you want a 3A or more 17mm buckdriver, with half-decent firmware, does that exist?

staticx57 · 2018-07-30T20:05:36.000Z

maukka:

djozz:

I think anything higher than 720nm will appear pretty invisible.

The OP in the reddit thread said

I have some 730nm LEDs, and I built a flashlight from a 3 watt one. When I take this light into a room and shine it on my black fabrics, the fabrics shine back red. Even more interesting is the fact that if the black fabric had been written on with black permanent marker, the writing becomes readable. Far-red LEDs make any other red LED look a bit orange by comparision

At least he sees them as red. Of course we don’t know if the ebay LEDs are actually 730nm. I wonder who would have equipment to verify those…

The Osram’s I posted? The i1 Pro I have clips at 730nm but I can assume this is a safe conclusion.

XPE Photo Red

Osram