The MagPi - February 2020

I

t’s well-documented that Raspberry Pi was

created to help get people into computing,

interesting them in a way that many

people were during the 1980s. Dewan Pieterse,

formerly of the University of Cape Town, worked

on a system to help school and other university

students get interested in radar.

“The radar introduces the user in an easy

and accessible way to electronics, [as well as]

embedded systems and how radar detects return

signals and performs filtering to measure radial

velocity and distance to objects,” he explains.

Making radar technology accessible to students with help from Raspberry Pi

Audio radar

Dewan

Pieterse

An electronics

engineer whose

mechatronic

engineering project

for university made

excellent use

of radar.

magpi.cc/

audioradar

MAKER

The radar is based on a Raspberry Pi 3B which

hosts a web server to enter the parameters needed

by the radar to operate. “The web server can be

accessed by connecting to the ‘RadarPi’ WiFi and

starts to broadcast upon power-up,” says Dewan.

“It is also used to display the results obtained after

the radar was operated.”

What’s in a wavelength

Normal radar uses radio waves (it was originally

an acronym for RAdio Detection And Ranging);

however, this version employs 8 to 12kHz of noise

to measure distance – using the reflection time

of the sound – and velocity, by making use of the

Doppler effect. Parameters can be modified on

a webpage generated by Raspberry Pi, allowing

students to see how different settings change

the results.

“The radar proved to be a minor success in

measurement of velocity, [although] with not the

desired resolution and clarity due to the automatic

gain of the microphone,” reveals Dewan. The

automatic gain of the microphone automatically

adjusts the received signals so that the signal

never clips on the voltage range. When the velocity

of a car is being measured, the microphone is

overwhelmed by the road noise and the resulting

plot is a quite faint line representing the velocity of

the vehicle.

Dewan’s RadarPi software enables the user to enter radar

parameters via an easy-to-use web interface

The radar system

can sense distance

and speed to varying

degrees of accuracy

The innards of the

device include a

Raspberry Pi, USB

sound card, amplifier,

and loudspeaker

16 magpi.cc Audio radar

PROJECT SHOWCASE