Measure the distance to an object within 25 cm to 8 meters using standard 40 kHz transducers. Takes around 20 samples per second.
Very useful for robotics! The first v2 version takes only 5 mA at 9v. The schematics are based on a project from Elektor dating from 1982!!!
Here again, the NOKIA LCD has been chosen for display. The circuit is controlled by a PIC16F877 running at 4 MHz.
At 20ºC/68ºF, sound travels through the air at 343,8 m/s. This is approximately 29µs for 1 cm.
We want to measure the distance to an object. To do so, we will have to measure the time between the transmission & the reflected reception of an ultrasonic pulse.
Because the reflected pulse will travel twice until received back, we divide the speed by two. So, this makes 58µS for 1 cm.
This v2 version counts the amount of periods of 58µS it takes until the ultrasonic pulse is received back.
http://www.techdesign.be/projects/008/008.htm
