On Feb 11, 2009, at 8:49 PM, alan smith wrote:

> Do the standard crop of IR recievers (30,33,36KHz etc) have the  
> ability to distiquish between the frequencies?  I want to have two  
> channels of IR going at the same time, and essentialy right next to  
> each other or will they get confused?

They have a sort of "average" exponential sensitivity roll-off from  
their center frequency, usually as show in some nice graph in the data  
sheet  (for instance, if I read it right, the TSOP11.. series  
sensitivity drops off 3bB at fzero/7 from the target frequency.)   
So... as much separation as possible is a good idea.  (I know that the  
IRRC plane contingent manages to get by with more than one setup at  
opposite ends of the usual spectrum (30 and 40kHz?)

OTOH, I know someone tried to use 38kHz Sharp GP1UE261xk detectors as  
a drop-in replacement for 36kHz detectors that were discontinued by a  
supplier, and had it not work (You can buy the 38kHz sensors cheap!   
here: http://www.2dkits.com/zencart/index.php?products_id=8 )

BillW

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