[robinekf]

Hi. My Maqueen is incapable of following a line, because the sensor seems to be too sensitive: I put it on a suface (black, white, doesn't matter), the blue leds on top turn on, showing the sensors see an obstacle. The only time it does not react (leds switched off), is when it is held in the air. So I put it on a white surface with a dark line: the robot just crosses the lines even without blinking (noticing something).

Must be really about the sensors' calibration, as I've already gone through all the tutorials.

[nana.wang]

Hi, please confirm the version, is McQueen 4.0 or 4.1?
Please note that 4.0 line-tracking probes cannot be calibrated, and 4.1 can.

[robinekf]

Yes, I confirm that it is a 4.0. Nothing to do then, it seems.

On the other hand, the ultrasound sensor is a bit weird too. Randomly, it identifies the flat floor as an obstacle, and changes direction. I oriented the "eyes" a bit upward, but the problem remains.

Thank you for the reply, I helped me to see the problem is in the gadget itself. I should maybe look for another product that works properly.