Code for a simple radar setup using an Arduino UNO, HC-SR04 ultrasonic sensor, SG90 servo motor, and DHT11 temperature and humidity sensor.
First, the necessary Arduino libraries should be installed:
Both of these libraries can be found in the Arduino IDE's Library Manager under
Sketch > Include Library > Manage Libraries....
Next, the necessary Python libraries should be installed:
The Anaconda distribution of Python was used to install these libraries.
conda install -c conda-forge numpy pandas matplotlib pyserial
Before using the radar, calibration should be done to find the speed of sound in the environment you are in. The code is setup to do this in two ways:
-
Distance-Time Method
Setup the ultrasonic sensor a set distance away from a flat surface and measure the time it takes for a ultrasonic wave to return. Dividing the distance by the time returns the sound speed. -
Atmospheric Method
Calculate the speed of sound based off of ambient conditions including temperature, relative humidity, pressure, and CO2 concentration.
The data for these methods is recorded at the same time. Set your ultrasonic sensor a
known distance away from a flat surface. Change the distance parameter in the
calibration.ino file to reflect your setup. Upload the calibration.ino file to your
Arduino and run calibration.py on your computer. This will record the temperature,
relative humidity, and speed of sound every two seconds while running. Press CTRL+C
to stop the program and print the mean values of the session. You can use the speed of
sound displayed at this point, or a more accurate speed of sound can be calculated
following the instructions in the calibration folder.
Once the speed of sound is obtained, update the value in the radar.ino file, then
upload it to your Arduino. Run the radar.py file on your computer to start requesting
data from the Arduino. It will be plotted in real-time in the popup graphical interface.
On Linux, one possible issue may be that you do not have permission to read the
/dev/tty* ports. I found that following this
answer and adding myself to the dialout group allowed me to read the files.