QTR-L Array

I am putting together small array with 3 QTR-L sensors (the right angle ones) to track the position of plastic filament using the line following function. The documentation mentions spacing the sensors apart at a distance that is appropriate for the size of the line, but doesn’t give any guideline for what that would be. For tracking a line from 1.5mm to 3.55 wide, how close should the sensors be to each other for effective tracking?


In general, you would want to have the sensors positioned in such a way that one of the sensors is always detecting the line (i.e. the line cannot disappear from sensor visibility when between two sensors). However, it seems like you are trying to detect something very thin and would not be able to position the sensors close enough together to achieve that. I also suspect that these sensors might have difficulty detecting something so thin.

  • Grant

If I used a row of photoresistors with an LED or line laser shining on them and created a “line” by casting a shadow on them, could I pretend they are analog QTRs and use the QTR library with them? Either one is sending a voltage between 0 and 5 to the analog pins, so the library doesn’t need to know they aren’t actually QTRs does it? By casting a shadow I can create a line that is big enough to measure.

You could use the QTR library if the sensors you are using have similar outputs to our QTR sensors. You might try implementing your proposed solution, but I am skeptical that it will work.

  • Grant