Sensors used on faucets, trashcans, etc.

http://www.aliexpress.com/wholesale?SearchText=Infrared+Reflectance+Sensor&catId=502&manual=y

Newark.com has these devices also.

These can be had for about $0.18 each but look at the external part$ count!  Just like some projects benefit from multiplexed LED outputs, I think these will need multiplexed input processing (and TDM control of the emitters, else adopt token ring methods ).  I am thinking like when they are placed all around the perimeter of a mobile robot.  But, how does one do that most effectively within the Hardware/Software Continuum of Design Choices?  Thanks for bringing this up - it really stimulated my thinking.  Seriously, I need some expert opinions on the integration of this sort of device. Are there other devices that incorporate emitter/detector pair with indicated external parts available today (E/D and op-amp and digital potentiometer) into one convienent I2C package?  So we need a three wire package, TI & Dallas Semiconductor:"Are you listening?",  with Vdd, Vcc, and i/o Data.  Where are these units and cost effective mass produced weather proof flexistrips? https://www.adafruit.com/products/346

Insight1:  They need to be mounted "linearly" so the plastic shield wall isolates every ir detector from all adjacent emitters.  Therefore, on a conic section device mounting line the E/D packages must be mounted with IR emitters "facing" each other and thus there must always be an even number devices distibuted along the conic section mounting line for monitoring in all directions (360 degrees) if the robot is to be free roaming in the environment.

Insight2: If each emitter pair (180 degrees out of phase for emitter pairs, that is to say interleaved) were uniquely modulated and the modulation could be determined post reception incorporating the relative location of the detector(s) providing the indication of reflected signal, then a relative position vector from robot is directly known if each device's (emitter source & detector) ID is provided to the post processor . Let's not forget there may be a detectable Doppler effect on the the received signal(s) which indicates speed of approach/recession of the detected object(s).  This is quickly becoming very complicated!  But there are smarter people than I who have already sorted this out; of that I am sure.

Downside: Cross talk confusion if multiple reflected signals are received simulatiously by a single detector.  Possible solution: refocused alternate scan method (multiple token types predefine scan pattern/focus) of selected emitter/detector devices that can further define and isolate reflectance source's relative position vector and  it's speed of approach or recession.  Who wants to head up the Robot Advanced Enviroment Detection Standards Committee (RAEDSC)?

Darkside:  What about objects or devices that are nonreflective by their nature or evil design?  What about intellegent objects that monitor a robot's emissions and jam it's detectors with intentionally false feedback signals?

http://www.aliexpress.com/wholesale?SearchText=Infrared+Reflectance+Sensor&catId=502&manual=y

Newark.com has these devices also.

These can be had for about $0.18 each but look at the external part$ count!  Just like some projects benefit from multiplexed LED outputs, I think these will need multiplexed input processing (and TDM control of the emitters, else adopt token ring methods ).  I am thinking like when they are placed all around the perimeter of a mobile robot.  But, how does one do that most effectively within the Hardware/Software Continuum of Design Choices?  Thanks for bringing this up - it really stimulated my thinking.  Seriously, I need some expert opinions on the integration of this sort of device. Are there other devices that incorporate emitter/detector pair with indicated external parts available today (E/D and op-amp and digital potentiometer) into one convienent I2C package?  So we need a three wire package, TI & Dallas Semiconductor:"Are you listening?",  with Vdd, Vcc, and i/o Data.  Where are these units and cost effective mass produced weather proof flexistrips? https://www.adafruit.com/products/346

Insight1:  They need to be mounted "linearly" so the plastic shield wall isolates every ir detector from all adjacent emitters.  Therefore, on a conic section device mounting line the E/D packages must be mounted with IR emitters "facing" each other and thus there must always be an even number devices distibuted along the conic section mounting line for monitoring in all directions (360 degrees) if the robot is to be free roaming in the environment.

Insight2: If each emitter pair (180 degrees out of phase for emitter pairs, that is to say interleaved) were uniquely modulated and the modulation could be determined post reception incorporating the relative location of the detector(s) providing the indication of reflected signal, then a relative position vector from robot is directly known if each device's (emitter source & detector) ID is provided to the post processor . Let's not forget there may be a detectable Doppler effect on the the received signal(s) which indicates speed of approach/recession of the detected object(s).  This is quickly becoming very complicated!  But there are smarter people than I who have already sorted this out; of that I am sure.

Downside: Cross talk confusion if multiple reflected signals are received simulatiously by a single detector.  Possible solution: refocused alternate scan method (multiple token types predefine scan pattern/focus) of selected emitter/detector devices that can further define and isolate reflectance source's relative position vector and  it's speed of approach or recession.  Who wants to head up the Robot Advanced Enviroment Detection Standards Committee (RAEDSC)?

Darkside:  What about objects or devices that are nonreflective by their nature or evil design?  What about intellegent objects that monitor a robot's emissions and jam it's detectors with intentionally false feedback signals?