**Sensors Secured to AEV**
The reflectance sensors have a small phototransistor and a single infrared LED. These two things are connected to a voltage divider. If the voltage divider records a low output voltage, this means there is greater reflection (the aluminum tape). The Arduino will record each time a non-reflective surface passes over the sensor as a “mark”. From here, the AEV can determine how far it has gone in mark units.