Make: Sensors

Chapter 3. Distance

How far is it? An ultrasonic distance sensor is one of the most popular sensors in the embedded courses we teach. A robot must know when an obstacle is near if it is to navigate around it. And isn’t it more convenient to just wave your hand in the air instead of clicking a physical button? A burglar alarm can detect an intruder by noticing change in distance or heat pattern. Your home, office, or school probably has an alarm like that.

The two most common ways to measure distance are sound echoes and light reflection. To avoid annoying people with constant beeping and blinking, the sound frequency is usually so high that humans can’t hear it, and the light frequency is so low humans can’t see it. The high-frequency sound is ...