QTR-8A ink type

I am having wildly dufferent results from this sensor depending on the paper an ink. If I print a line on matt paper using a large fornat paper it sees the black as white( calibration shows min and max the same). I have similar results with coated (shiny) paper which I get but the paper I’m trying is matt. I get great results with our bw printer on ordinary paper but that’s only snall sheets and cannot print the large sizes I need.

Any advice?


The QTR sensors depend on the reflective properties of the materials or surfaces you are measuring, so it is possible that particular combinations of gloss or matte paper with different kinds of ink might work poorly. A combination of materials we have typically had good contrast with and recommend for line following courses is white posterboard and black electrical tape. You might try getting a small test piece of posterboard with electrical tape and see what kind of results you get. If it does not work as expected, there might be something wrong with your setup (such as having the sensor too far from the surface). If it works well and you are interested in making a whole course, you might find the “Building Line Following and Line Maze Courses” guide helpful in doing so.


Yeah the electrical tape works well. We have an hp large format printer at work and hoped to print a large course but it fails whichever paper I try.

Yep, it seems printing on my colour laser printer on any coated paper fails. Using a standard bw photocopier is fine. Hp large format fails on all paper.

However, used our large format plotter, type used for large architectural plans, and it works a treat. Printed A0 (119 x 84cm) and great calibrations. As good as electrical tape.