The MagPi - February 2020

For distance measurement,

the radar proved to be a

major success, with the

only downside being the

resolution of the plot

Distance is

calculated by

measuring the time

between the sound

being emitted and

then received

after reflection

“For distance measurement, the radar proved
to be a major success,” he adds, “with the only
downside being the resolution of the plot. When an
object was measured at a set distance, the results
would display the range ±10%. However, the known
distance was always in the middle of the range and
therefore a successful measurement. The reasons
for the variation in distance was not investigated
due to a time constraint, but initial tests proved
that the automatic gain might be to blame.”

Accessible radar
Dewan’s system continues a long-running theme
of projects involving radar, with this iteration
trying to make it as open, affordable, and
accessible as possible – which is why a Raspberry
Pi was involved: “Raspberry Pi offered built-in
wireless LAN and sufficient RAM capacity to host
a web server,” says Dewan. “Other embedded
systems, such as the STM32F04, were also
considered, as a lot of previous work was done on
this and the on-board analogue-to-digital (ADC)
was also attractive. The STM and other Arduino-
based systems had insufficient storage and RAM
capacity, and therefore Raspberry Pi offered a
superior solution.”

> QR codes are

used to access

Raspberry Pi

> Dewan has

since graduated

from UCT

> Ultrasonic sensors

in robots use a

similar system to

detect distance

> Sonar uses

sound, but is

usually employed

underwater

> Sound radars can

also be known

as SODAR (SOnic

Detection And

Ranging)

Quick FA C T S

Audio is played through

the speaker, either in a

continuous tone or in pulses

A microphone listens for

the reflected audio so

calculations can be made

A web server is

powered by Raspberry

Pi and allows users to

tweak the experiment

Audio radar magpi.cc 17

PROJECT SHOWCASE