Servo - December 2016

Some would argue that adding tilt compensation is going overboard and that small educational bots do not need it. If you want a more accurate heading, use:

dir = compass.avg_heading(mydeclination, 5)
# 5 is the number of samples to average

Unfortunately, as we cannot mount the compass and accelerometer perfectly flat (with respect to the floor), the error can be quite large (easily more than five degrees) without tilt compensation, even after we account for magnetic declination.

Sadly, even with correction for magnetic declination and tilt compensation, we will still be disturbed by the wiring and metal present in a house. However, the results should at least be repeatable within the same house. This can easily be demonstrated by using a compass app on your phone, or an actual old-school compass.

Turning Berry in a circle and occasionally tilting him presented better results when tilt compensation was applied.

Mission Accomplished

In the next column, I will: • Add wheel encoders so I can track distance traveled • Add an HC-SR04 ultrasonic ranger as it has a four meter range compared to the 1.5 meter range of the current infrared sensor (I may remove the short-range IR sensor)