Pololu Robotics & Electronics
My account Comments or questions? About Pololu Contact Ordering information Distributors

Pololu Forum

Black on black line sensing


I’m currently working on a project where I want to follow a shiny black line on a mat black surface. The surface is glass. I have had previous experience with the QTR-8RC sensors when it comes to following a black line on a white surface. When I tried to use the sensor for my current project it does not see the difference between the shades of black (visually there is a big difference).It sends back full absorption values for both shades. Is there a way to calibrate the sensor so that it is more sensitive in the high absorption range? Or is this sensor not right for this application. I am desperate for any information regarding this topic, since I cant find information on it online, So any feedback is appreciated.





In general, less reflective surfaces require a longer reading time than a more reflective surface. If you are using our qtr-sensors-arduino library, you might try running the QTRRCRawValuesExample.ino sketch to see what specific raw values the sensor is returning. If the sensors are all returning 2500 microseconds, you might try increasing the TIMEOUT constant until you see values returned that are lower than the timeout for all of the sensors over both surfaces.



Hi Nathan,

Thank you for the suggestions. I will give these a go.