Reflectance Sensors – As seen in the image one the sensors are mounted behind the wheel. The wheel has two discontinued reflective surfaces. As the wheel rotates, the infrared light is reflected by the reflective surface and absorbed by the black surface so one rotation of the wheel will result in (1 0 1 0) where 1 is when the infrared light is reflected and 0 means that light is absorbed. The arrangement on the other side can be seen in image two, there are two sensors, and the wheel is removed from the mount to show the reflective surface. Image three shows the complete arrangement.
The diameter of the wheel can be measured using a vernier calliper, and then the circumference of the wheel can be used to calculate the number of rotations required by the wheel to cover the whole track. The AEV needs to stop when it approaches the gate. Arduino has to be coded in such a way that it stops just before the gate and then wait for the gate to open and then move and then again move and stop at the end of the of the gate. This property of the refractive sensors makes the AEV track dependent. Hence, it needs to be re-coded if the track is changed.
(Image one) (Image two) (Image three)
