Mounting multiple 940nm LED bulbs

gth

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in short -
My question is whether anyone has any experience or even just ideas on the best way to mount a lot of fiddly little LEDs. Right now I have a kind of writer's block on how to put this together from a DIY perspective.

As background / explanation -
I've tried the IR lights in my cameras + IR illuminators, but between the reflection from the eaves and cameras pointing at each other, it's just not working for me. Given the larger distances involved (30-50m usually), I want to take a different approach.

I've been able to source a bunch of 940nm LEDs (yay, no visible red lights!) and I don't mind soldering them + resistors & powering them dusk to dawn myself (either POE or using AC power with conversion, relays, etc).

My general idea is to run a whole lot of these LEDs around the edge of the eave trim, pointing back at the wall of the house. The aim being the house should then be visible on any of the cameras and maybe silhouetting would aid movement detection [and maybe later on trigger relays on normal lights, as kind of faux sensor lights]. I totally understand these tiny LEDs aren't going to achieve any kind of outward-facing flood lighting effect.

Because there would no longer be intense clusters of super-bright IR LEDs from the cameras/illuminators, I'm hoping it will be a good way to achieve some general night time lighting of the house. I have some distance all around the house to play with (10-20m), but it's flat ground - no landscaping or other fixtures to hide any lighting in.
 

wittaj

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The problem is at that distance it may not work, and some of the cameras cannot see that light or see it very well.
 

TonyR

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I would think the labor, time and expense of mounting LED's, installing current limiting resistors, packaging to protect from water, etc. would be an expensive, time consuming and a very difficult project. Based on that, but also knowing little about the practical needs of your situation, maybe the LED light strips could factor in. They are available in 940nm wavelength, some are waterproof and some can fit into mounting strips, some as long as 16 feet in length. Most are also conveniently 12VDC so even a POE to 12VDC splitter could be used on the 24W versions. They come in versions all the way up to 72W. I was envisioning a row of these under an eave, projecting down the house walls like a wall washing light. The eave would disguise them and protect them even further from direct UV and rain. I cannot attest to these but maybe a small scale experiment would prove this usable or not.

IR-strip_940.jpg
 
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TonyR

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Another note: You possibly already know this, but most cams are optimized to see 850nm IR; they can see 940 but its effect is reduced so more intensity of 940 is required as compared to the 850. That overall intensity requirement translates to needing more of them in a given area, I would imagine.

I've read estimates that cams are as much as 20% less sensitive to 940 than 850.
 
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I think that number of 20% needs to be in context. That means if 850nm is 100% seen by a camera, the 940nm will only be 20%, 1/5th, as bright meaning you'll need at least five times as much light at 940nm to get the same amount of light to be seen by the camera. Have a look for a thread talking about license plates in Tennessee. There's a long discussion there regarding this exact problem and, if I remember correctly, many cameras won't see 940nm at all because the IR vision is tuned to 850nm.
 
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gth

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Appreciate for all the detailed replies - thank you.

I think that number of 20% needs to be in context.
I noticed while bench testing the 940's that they didn't appear to light up the nearby area very much, but I didn't have some 850s nearby to compare with (also it wasn't night time - just pulled the shades in the shed). I might also think about diffusion of some sort given the torch-like focus of the LED bulb shape.

I agree that strip lights of 940s would be the easiest; I guess I'm essentially trying to reinvent the wheel in that sense. Nothing I come up with will be easier and, factoring in the time and effort, nor will it be cheaper.

Pondering for a while, the closest I came up with is some timber trim with two channels cut along them, and drill out regular holes so the LEDs just poke out. The two channels being the +'ve and -'ve lines, and a small cutout at each LED point for the resistor.

It would take some trial and error testing to find out how many LEDs per metre are required, depending on how much light the cameras can pick up.
 
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All I can say is to be ready for an awful lot of them to even come close to an 850nm IR flood light. Without a lens to aggregate the light it'll be even worse. In that license plate thread one of the guys had an expensive high power IR illuminator made with a spotlight lens trying to get license plates at about 120 or 150 feet. It didn't work.
 

wittaj

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Heck, once you dial in these cameras to eliminate motion blur (with faster shutter speeds of at least 1/60s), your quoted distance of 30-50m is almost impossible with onboard IR that the camera is designed to see, so it will be impossible with 940 at that distance. I think you will go to all this effort and find that it doesn't help at all.
 
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