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Finding near IR LEDs is difficult

A project log for Hoodlight

Add personal lighting to any hoodie for style and optional anonymity.

Chris HamiltonChris Hamilton 08/17/2015 at 18:062 Comments

We have tested a few very expensive LEDs, but nothing that comes in a strip so far emits only near IR. Usually they are quite red too.

Discussions

davedarko wrote 08/20/2015 at 19:17 point

I'm wondering how hard it can be to make a strip based on the needs of this project. What do you mean by "near IR" exactly? What wavelength do you need for the CCTV? Following this webpage you need about 840nm? http://www.camsecure.co.uk/InfraRedCameraResponse.html 

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Chris Hamilton wrote 08/21/2015 at 00:24 point

Well that depends on what effect you are going for.  That would be trying to help the camera see you better at night, where we are going for over exposure with the day IR filter on.  Very very bright 850nm will(should) over expose cheap CCTV (cheap is the rule more than the exception).  I can mock up a version like that and even test it with cameras I have.  We were hoping for more anti phone camera too.  Either way, the effect is going to be dependent on camera quality and strip placement.  740nm-780nm seems to be a good spot that passes IR filters and still is not really human visible.  We have been testing this along with the Social Light project  (where the near IR ideas came from), neither of which we are 100% sure about reliability of the effect.  So far we bought a wide range of individual 3528 LEDs from Starsealand.  They did not emit a precise wavelength like the more expensive LEDs I have in the range.  I need to order another batch in other packages to see if it was a fluke as well as identify other manufacturers.  Ideally, we would just run with an off the shelf IR strip, but obviously it is hard to find specific wavelengths and I just haven't had the budget to buy a range of full strips to test.

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