Photoelectric Speed Sensor Encoder Coded Disc code wheel for Freescale Smart car

Hello and welcome back to a robotic series. In our last video, we figured out how fast the motor is spinning and what direction it was moving. But we don't know how far it's traveling. To do that you might think that we could set a throttle value and just give it a certain duration, track how far it's gone, and use that as a calibration for the distance traveled. But the problem is that the battery voltage is going to change. If you remember from our last video, that's what dictates how fast our motor is moving. So as our robot is driving around, it's draining the battery and the voltage is decreasing. And if we look at these PWM graphs on the oscilloscope, we can see that a fresh pack of batteries gives us about 6 volts for our peak voltage. And a drained battery is going to drop down to about 5 volts. So we can't use that to measure the distance. But we can use an encoder. And that's