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TechniSol · 03-28-2013, 07:09 PM

Peakcrew,

Gads, it's been years since I initially researched, but the hard and fast rule of thumb was don't assume just because it won't pass visible or appears opaque that it won't pass IR... test it. You have an IR sensitive camera, a TV remote makes an OK, if a bit dim, IR source for testing. A piece of exposed/developed 35mm negative appears black, but passes IR and blocks visible pretty well.

My tag blaster designs pumped nearly 10amps through the IR LED at a very low duty cycle for a very short period of time(just long enough to transmit 8-10 characters @2400bps and employed a pseudo manchester encoding so for every high bit there was a coresponding low bit or break) and employed a simple lens to concentrate the beam -I think my max "rate of fire" was no more than 5 shots per second, but I may have gone as high as ten. Got me about 360' range in full sunlight aiming with a red dot scope and transmitting who shot you.(Blaster # which was matched to a name or handle in a teensy database maintained on each microcontroller)

It's been 4+ years since I played with the code. The other thing was absorption(important to arena play), flat black spray paint works like a charm to absorb IR as it's apparently mostly carbon particulates in nature.

I eventually tracked down a visible light blocking deep reddish black plastic that looks completely opaque, but transmit's around 93-98% IR @ 880-940nm frequency. I found a company near Las Vegas that would sell me less than full 4'x8' sheets of it.

They absolutely would not discuss what products they molded with it, but if I had to guess the casinos can see every card that's dealt as well as laid on a dark plastic looking playing surface, just to keep card "mechanics" honest...

Bear in mind said surface might easily be disguised with a fabric covering that also appears opaque, maybe even greenish in visible light. Probably makes nice table surfaces for Poker, Chemmy, Blackjack, and those euro rooted games for people that apparently can only be bothered to count to 7 or 9...

I'm sure any black looking expanse of plastic in the decor probably hides an IR camera as well.

03-28-2013, 07:09 PM	#357
TechniSol GranPohbah-Fezzes r cool! Posts: 1,056 Karma: 3151024 Join Date: Jul 2010 Device: Nook STRs, Kobo Touch, Kobo Glo	Peakcrew, Gads, it's been years since I initially researched, but the hard and fast rule of thumb was don't assume just because it won't pass visible or appears opaque that it won't pass IR... test it. You have an IR sensitive camera, a TV remote makes an OK, if a bit dim, IR source for testing. A piece of exposed/developed 35mm negative appears black, but passes IR and blocks visible pretty well. My tag blaster designs pumped nearly 10amps through the IR LED at a very low duty cycle for a very short period of time(just long enough to transmit 8-10 characters @2400bps and employed a pseudo manchester encoding so for every high bit there was a coresponding low bit or break) and employed a simple lens to concentrate the beam -I think my max "rate of fire" was no more than 5 shots per second, but I may have gone as high as ten. Got me about 360' range in full sunlight aiming with a red dot scope and transmitting who shot you.(Blaster # which was matched to a name or handle in a teensy database maintained on each microcontroller) It's been 4+ years since I played with the code. The other thing was absorption(important to arena play), flat black spray paint works like a charm to absorb IR as it's apparently mostly carbon particulates in nature. I eventually tracked down a visible light blocking deep reddish black plastic that looks completely opaque, but transmit's around 93-98% IR @ 880-940nm frequency. I found a company near Las Vegas that would sell me less than full 4'x8' sheets of it. They absolutely would not discuss what products they molded with it, but if I had to guess the casinos can see every card that's dealt as well as laid on a dark plastic looking playing surface, just to keep card "mechanics" honest... Bear in mind said surface might easily be disguised with a fabric covering that also appears opaque, maybe even greenish in visible light. Probably makes nice table surfaces for Poker, Chemmy, Blackjack, and those euro rooted games for people that apparently can only be bothered to count to 7 or 9... I'm sure any black looking expanse of plastic in the decor probably hides an IR camera as well. Last edited by TechniSol; 03-28-2013 at 07:12 PM.