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I advise using 1 i/o per qti, and isolate each sensor.
To check if your sensor is working use a camera to see if the ir light turns on. All digital cameras , as far as I know, are able to see ir light, as a bright white blob. If you want to make sure your camera can see ir you can just point a tv remote at the camera and push any button.
B: goes to groundR: is the signal wire (weird I know)W: is connected to poweryou should also connect a 10k resistor between R and W. The 10k resistor is a pullup which allows for a digital output HIGH for black and 0 fr white. With this same setup you could connect the signal wire to an adc to use it as an analog sensor. Parallax recommends that you should use 2 i/o pin for one sensor. The reason is you can prevent interference from multiple sensors if you only turn on one at a time. I advise using 1 i/o per qti, and isolate each sensor.To check if your sensor is working use a camera to see if the ir light turns on. All digital cameras , as far as I know, are able to see ir light, as a bright white blob. If you want to make sure your camera can see ir you can just point a tv remote at the camera and push any button.***NOTE***make sure the sensor is in pretty close proximity to what ever you are analyzing.
The QTI sensor is activated by placing 5 V (Vdd) on the W pin. This will cause current to flow through the 470 ohm resistor to the LED side of the QRD1114. IR light reflecting of the surface below will cause a change in the ability for the current to flow through the phototransistor side of the QRD1114. The transistor, in effect, behaves like an IR controlled resistance.
How? Would you just always have the IR emitter on and just read the receivers signal?
then take a reading,
'PARALLAX QTI SENSOR SYSTEM TESTQTI VAR WORDLOOPHIGH P1HIGH P0PAUSE 1RCTIME P1,0,QTILOW P0DEBUG [DEC QTI, 13]PAUSE 200GOTO LOOP