I have an ultrasonic sensor attached to the Arduino with a sketch that calibrates the distance and after that, it triggers a signal when something crosses the detector.
When the detector is attached to the breadboard everything is fine. I've put the sensor into a case with a cable (aprox 1,2 meters). When the cable is extended, everything is fine, however if I leave some cable still rolled on itself, it detects no motion.
The sad thing is I read about somthing like that but at that point I wasn't interested in US sensors so I didn't pay much attention and now I seem unable to find the article/blog/post about it. I would really much like to know why does it happen and whether or not can I do something to improve the design.
Thanks in advance.