http://homediyelectronics.com/projects/arduino/arduinodistancesensor/ Sensing the proximity of objects can be achieved effectively using ultrasonic echo techniques. Transmitting pulses of ultrasonic sound and measuring the time it takes the echo to return does present us with some interesting challenges however.
The sound can bounce off more than one object at different distances or the pulse is scattered. Sometimes the receiver doesn’t even hear the echo. Luckily these problems can be overcome and a useful instrument built using an HC-SR04 ultrasonic transceiver and a little clever software running on an Arduino.
Transcript: Hi I’m Steve Garratt from [...]