QTI Sensor Range
Humanoido
Posts: 5,770
Is it possible for the QTI sensor to work with a range of several inches for "obstacle avoidance" and not line following? I understand this would exceed the very small recommended range for line following.
Comments
I did some tests today using a quickstart (QS) and Kye's D8C_QTIDemo code.
I had the QTI laying face up on the desk and used a white 3 x 5 inch card as a target.
Using the QS 3.3V supply as power for the QTI the range to start seeing a change in value is around 3/4 inch.
Using the QS Vin (around 4.3V) the range improved to around 1 inch.
Two factors are limiting range.
1) The D8C_QTIEngine samples the QTI output for 1ms, with distant targets the output does not fall low enough to be detected within this time.
2) The dropping resistor on the IR LED on the QTI is 470 ohms, this limits the current to around 6mA. The datasheet for the QRD1114 used in QTI indicated the max continuous forward current for the IR emitter is 50mA.
I altered Kye's code to sample the QTI output for 2mS and was able to detect the card at around 2 inches.
Changing the 470 ohm resistor to 100 ohms would be safe for either 3.3V or 5V supplied and should extend the range, but I have not tried it.
I would say that in general the stock QTI sensor would not be a good sensor for general object detection at the range you are looking for.
C.W.