[TriEmbed] TriEmbed Digest, Vol 39, Issue 16

[Pete Soper]

Shane makes an excellent, if not crucial point: by using interruption of 
a modulated carrier you can know when the "beam" is actually present and 
unambiguously detect beam breaks from the light going to/from the 
reflector. You could even borrow from the RF world and adjust the 
emitter brightness until your SNR is good in varying conditions, with 
varying distances, etc.

-Pete


On 08/23/2016 01:49 PM, Shane Trent via TriEmbed wrote:
> Chip,
>
> I have read about LED based long range systems that uses lenses to 
> focus the beam. If you are going to focus the beam to hit a 
> retro-reflector target (I wonder if SOLAS tape works better than 
> bicycle type reflectors?). I would try to test the setup with Red LEDs 
> to get you in the ball park visually. I suggest using a modulated 
> carrier and an IR receiver that detects the carrier.
>
> Pololu has some receiver modules that might be handy (fixed and 
> adjustable gain, not sure which would fit your application better). 
> They also have modules with a modulator and receiver on one board but 
> it looks like their low power version use 8 ma. However they are not 
> using retro-reflective targets. The Pololu IR modules might give you a 
> fast and dirty method to explore the performance envelope of your 
> proposed setup without requiring much engineering time.
>
> https://www.pololu.com/blog/272/new-products-vishay-38-khz-ir-detector-modules
> https://www.pololu.com/product/2461
>
> Shane
>