Project #3A - Odometry

In this project, we are going to play with the hardware that will eventually be used to implement wheel encoders on the Trinity Robot projects. Each team will build the schematic above with the P5587 photoreflective sensors we have in the lab. Breadboard the schematic above and verify that it works by putting reflective (white paper) and nonreflective material (black paper) about 5 mm in front of the sensor and measuring the digitial output of the circuit with a volt meter.

Once you have verified the photoreflector circuit, make a sensor cable and connect it to a digital input on the Handy Board. The Handy Board has a 47 KOhm pullup resistors on analog and digital inputs. A small ceramic disc capacitor of 0.01 uF or higher should be placed across 5 V and GND.

Write a simple program to count the number of transitions from reflective to nonreflective material and write that number to the LCD screen.

Materials:

• a P5587 or P5588 photoreflective sensor
• resistors R1 and R2
• reflective and nonreflective material
• a solderless breadboard
• connectors for interfacing with Handy Board
• 0.01 uF or higher capacitor
• a test pattern with white and black regions printed on a test strip---you will move this through the sensor manually to test your pulse detector/counter.

• Report the voltage on the photoreflector output with reflective and nonreflective material.
  • What voltage does the Handy Board require to see logic low? What voltage does it need to see logic high?
• Look at the datasheet for this photo reflector. Discuss any delay introduced by the sensor. How many pulses per second can this photoreflector detect? How well will it work for your robot?