Chapter 7 Summary

This chapter focused on using a pair of infrared LED emitters and receivers to broadcast and detect reflections of 38.5 kHz modulated infrared light. Using this sensor system for robot navigation used these concepts and skills:


  • What an infrared LED is, and how to identify its anode and cathode.
  • What a modulated infrared receiver is, and how to use it in a microcontroller circuit
  • What effect resistor values have on LEDs when connected in series


  • How to use the familiar Arduino tone function for a new purpose: to modulate an infrared light signal, instead of control the pitch of a sound
  • How to repurpose an existing sketch from one sensor system for use with a different sensor system, so long as both sensors have a similar output signal
  • How to repurpose an existing sketch designed for a specific behavior (avoiding obstacles) to a new behavior (detecting a drop-off)

Robotics Skills

  • Using a pair of infrared emitters and receivers to detect objects  for non-contact autonomous sensor navigation

Engineering Skills

  • Using human-visible indicators (red LEDs) to broadcast the state of sensors detecting human-invisible conditions (reflected modulated infrared light)
  • More practice with subsystem testing and troubleshooting