Infrared

[cole7011]

Any chance someone can tell me the theory and method behind infrared transmission and reception, how it works etc...  universal circuit requirements...

basically the principal behind it, etc etc...

many thanks

mcole

 

[Lou1]

Hi

Here is a small primer on the subject to begin with:
http://www.web-ee.com/primers/files/an1016.rev0.pdf

 

[Kevin Weddle]

Infrared is used in digital transmission. Since it is a transducer, it is not accurate enough in theory to transmit analogue signals. You might even choose to use something other than infrared. It all depends on the wavelength expected by the photodetector.

 

[cole7011]

thanks, but how does a Phototransistor work, what is the typical method of converting the output in to a useable signal for activation of say a relay, How is rectified  ?  etc?

 

[audioguru2]

Kevin,
Infrared is used for wireless headphones and speakers. Since the response of a phototransistor is not very linear with amplitude, usually FM modulation and detection is used. I have seen huge arrays of IR LEDs in conference rooms for language translation. They are beamed to IR detectors that drive headphones.