Saturday, December 17, 2011

aBot – Wheel Encoder Mystery Solved (or So I Thought)

This morning I solved the mystery of the second wave.  It turns out the wheel is not exactly true and therefore as it rotates the distance between the sensor and the encoder disk varies slightly. 
How this affects the values is that as the distance varies the reflectance for the white and black lines increases when the sensor is closer to the disk and decreases when the sensor is further away.  This in turn consistently increases or decreases the discharge times for the capacitor which causes the peaks and valleys to form a wave as the wheel rotates.

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