Published November 10, 2020

Displacement vs. Time Graph Using an Ultrasonic Sensor

Use an ultrasonic sensor to make a Displacement vs. Time graph on Google Sheets for a pendulum, specifically, a speed bag.

BeginnerFull instructions provided2 hours748

Displacement vs. Time Graph Using an Ultrasonic Sensor

Things used in this project

Hardware components

Particle Argon

Jumper wires (generic)

Ultrasonic Sensor - HC-SR04 (Generic)

USB-A to Micro-USB Cable

Breadboard (generic)

Portable Charger

Software apps and online services

Particle Build Web IDE

Google Sheets

Hand tools and fabrication machines

Tape, Velcro® Stick On Tape/Strip

optional*

Story

Introduction:

I've been boxing for well around 3 years now and quite honestly, I still believe I'm at the same skill level as I was 3 years ago. So, what better way to put this theory to the test than to record my progress and measure how fast* I can punch a speed bag with a Displacement vs. Time graph? :-)

*Disclaimer: I use velocity and frequency interchangeably.

Hardware Setup:

Place the Particle Argon on the breadboard
Using a jumper wire, connect the GND pin of the Particle Argon to the "Gnd" pin of the ultrasonic sensor.
Using another jumper wire, connect the VUSB pin of the Particle Argon to the "Vcc" pin of the ultrasonic sensor.
Using a third jumper wire, connect D3 on the Particle Argon to the "Echo" pin of the ultrasonic sensor.
Using a fourth jumper wire, connect D7 on the Particle Argon to the "Trig" pin of the ultrasonic sensor.

1 / 2 • Wiring the hardware

Code:

Creating a Displacement vs. Time graph requires 4 things:

Assigning a value to "rest:" In other words, at what distance will the speed bag be at equilibrium? This should be your first call to getDistance(), assuming that the speed bag isn't moving.
Collecting time, like a stopwatch: Because we'll be graphing our data, we'll need to know the time of the position of the speed bag at all times. In other words, when the speed bag is at x position, y seconds have passed. We'll be using millis() to find time.
Collecting displacement: Displacement is a measure of how far away an object is from its starting position or equilibrium. We'll need to know how far away the speed bag is from equilibrium at all times.
Continuously publish two variables of data (displacement and time) to the Particle Console. To bypass the limitations of Particle.publish(), we'll be encoding the string as JSON (see lines 48-50).

Flash your Particle Argon will the code attached below.

Setting Up Your Google Sheets:

These next few steps are adapted from Gustavo Gonnet's "Pushing Data to Google Docs" project and the site he links as well. I'll be listing the relevant info here, but if you'd like a more in-depth explanation, take a look at their articles.

Go to Google Sheets and name the first two columns "displacement" and "time" respectively. It is incredibly important that your headers match the variable names you specified in Particle.publish().

This is what your spreadsheet should look like. Title doesn't matter.

Follow the "The Sheet" section on this website and make sure to save your script URL! This will be important for when we create the WebHook integration on the Particle Console.

Setting Up Your WebHook

Go to the Particle Console > Integrations > WebHook
Under the "Custom Template" tab, copy the following code, but change the URL to your own Google Script URL and deviceID to that of your own device.

The Setup:

Now that your code is working, it's time to put it to the test!

Place your ultrasonic sensor in a position where it is directly facing your speed bag.
Connect the Particle Argon to a portable charger or battery pack and wait until it's breathing cyan.
Wait a couple of seconds before punching your speed bag. Remember, the first call to getDistance() will assign a value to "rest" and you need to make sure the object is not moving until "rest" is assigned a value. Also, try to hit the bag as straight as possible.

Here is a picture of my setup:I hot glued a piece of plastic to the wooden beam facing my speed bag and secured the breadboard using velcro:

The Data:

After you've hit the bag for at least 30 seconds, disconnect the Particle Argon and check your Google Sheet. You'll see the data from your session.

An example of my data

In regards to some outliers, like displacement being 38.05 in my screenshot above, that is most likely due to the fact that at times, my speed bag traveled at an angle and not directly in line with the ultrasonic sensor. Since most of the data looks right, you can insert a "Smooth Line Chart" on Google Sheets by:

Selecting all data > Insert > Chart
Selecting "Smooth line chart" under "Chart Type"
Changing "X-axis" to "time" and "Series" to "displacement"
Changing the "axis-titles" to "Time (s)" for the x-axis and "Displacement (in)" for the y-axis.
Optional: further customizing your graph with a different color and displaying plot points.

This is what my graph looked like.

Analysis:

Using this image as a reference for what is defined as a "cycle, " count how many concave down slopes you have. My data has 9, but it will differ for everyone depending on how long you recorded data.

1 cycle is shown in red.

Once you have counted your cycles, you can divide that number by the total number of seconds your data recorded to find frequency (or "velocity").

Frequency = number of cycles/seconds

My frequency = 9 cycles/37 seconds = 0.24 hz (hz are the unit for cycles/seconds).

Beyond just frequency, the graph can give you important insight into what happened during that whole interval: the narrower the graph is at a given interval, the faster you were hitting the bag, and the wider it is, the slower you were going.

Code

ultrasonic-code.ino

#define triggerPin D7 // pwm/input
#define echoPin D3 //output

double rest = 0.0;

double startMillis = 0.0;
double currentMillis;
double elapsedMillis;

double duration, distance;

const double marginOfError = 0.3; // in inches
const double speedOfSound = 0.0135; // in inches

void setup() {
    pinMode(triggerPin, OUTPUT); // send pulses out from the Argon
    pinMode(echoPin, INPUT); // receives the pulses from the device
}

double getTime() { 
    currentMillis = millis();
    elapsedMillis = (double)((currentMillis - startMillis) / 1000.000); // in seconds
    return elapsedMillis;
}

double getDistance() { // returns distance from the sensor, NOT from equilibrium
    digitalWrite(triggerPin, LOW); // makes sure the trigger pin is clear
    delayMicroseconds(2); 
    digitalWrite(triggerPin, HIGH); // generates an ultrasonic sound wave 
    delayMicroseconds(10);       
    digitalWrite(triggerPin, LOW);
    duration = pulseIn(echoPin, HIGH); // measures the duration of a pulse in   microseconds
    distance = (duration / 2) * speedOfSound; // duration = time it takes for the pulse to go out + bounce back.
    return distance;
}

void loop() {
    if(startMillis == 0.0) {
        startMillis = millis();
    }
    if(rest == 0.0) { 
       rest = getDistance() - marginOfError;
    } 
    double displacement = (getDistance() - rest) * 1.000;
    double timeElapsed = getTime() * 1.000;
    char data[256];
    snprintf(data, sizeof(data), "{\"displacement\":%f, \"time\":%f}", displacemwnt, timeElapsed);
    Particle.publish("motion-detected", data, PRIVATE);
    delay(200);
}

Credits

Yamilett Estrada-Reyes

3 projects • 2 followers

Displacement vs. Time Graph Using an Ultrasonic Sensor

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction:

Hardware Setup:

Code:

Setting Up Your Google Sheets:

Setting Up Your WebHook

The Setup:

The Data:

Analysis:

Schematics

The Wiring Diagram:

Code

ultrasonic-code.ino

Credits

Yamilett Estrada-Reyes

Comments

Embed the widget on your own site

Displacement vs. Time Graph Using an Ultrasonic Sensor

Displacement vs. Time Graph Using an Ultrasonic Sensor

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction:

Hardware Setup:

Code:

Setting Up Your Google Sheets:

Setting Up Your WebHook

The Setup:

The Data:

Analysis:

Schematics

The Wiring Diagram:

Code

ultrasonic-code.ino

Credits

Yamilett Estrada-Reyes

Comments

Related tags