MEGR 3171 Fall 2023 Team 33:

•

Reece Walser

Published November 27, 2023

Upgraded RC Car | MEGR 3171 IoT Project

An RC Car equipped with an impact sensor and ultrasonic distance sensor.

IntermediateFull instructions provided1 hour123

Things used in this project

Hardware components

An RC Car

Particle Photon 2

Impact Switch Sensor

Ultrasonic Sensor - HC-SR04 (Generic)

Software apps and online services

Particle Build Web IDE

ThingSpeak API

Story

This is Tyler Hayes' and Reece Walser's submission for the Fall 2023 MEGR 3171 IOT project. This project required us to collect data using two sensors of our choice and two Particle Photon 2s. The publish and subscribe functions are to be used to enable both our Photons to communicate with one another. Finally, ThinkSpeak Webhook integration is to be used to graph data in real time.

Overview

Are you tired of boring old RC cars? Antiquated and boring machines that are incapable of collecting and sending data across the internet. If so, you're in luck, as our team's project allows you to upgrade any bland RC car into an IOT data-collection machine, capable of providing real-time information about how often you drive into things. By using an impact switch, ultrasonic distance sensor, and two Photon 2s such a feat is possible.

Hardware

The car we decided to use for this project is this BEZGAR TB141 RC car. The reason we chose to use this car, in particular, is because it has a couple of flat surfaces which we can use to place breadboards upon.

Image from the Amazon page linked above

Next, the impact switch sensor we used is this cheap switch we found on automationroboticsarduino.com. In hindsight, we believe a different sensor could have been a better fit for our project, as we realized we could only detect head-on collisions without the use of multiple of these sensors. For the purposes of this project, this shortcoming is not that big of a deal, so we used it anyway.

Image from automationroboticsarduino.com page linked above

The final sensor we used is an HC-SR04 ultrasonic distance sensor, which is a neat sensor for its low price. This sensor is capable of emitting ultrasonic waves, which echo back and are detected by the sensor. By measuring the time it takes for waves to return to the sensor and using the equation: Distance = (Speed of Sound * Time Taken) / 2, it is possible to determine the distance from the sensor to the nearest object.

Image from sparkfun.com page linked above

Putting it all Together

As previously stated, we selected a car for this project based on the location of flat surfaces where we could stick a breadboard. Due to the fact that the impact switch sensor we used is effectively more of a button, it is necessary for there to be a location to place a breadboard on the front of the car. Luckily, the hood of the car is a perfect fit for this. Using a breadboard with an adhesive on the back, we constructed our circuit (seen in the circuit diagrams at the bottom of this page) and stuck it on the hood of the car. We then used duct tape to connect the impact switch to the very front of the car, as seen in the image below. Since the impact switch isn't connected directly to the breadboard, it was necessary for us to use some female-to-male jumper wires to connect the sensor to our Photon 2.

Close-up of the impact switch sensor

Next, we set up the HC-SR04 ultrasonic distance sensor. Sticking a breadboard on the roof of the car, behind the headlights, we were easily able to construct the circuit (again, the circuit configuration can be found at the bottom of this page). It is worth noting that we needed to stagger the breadboard to hang off the side of the car, as the sensor would otherwise be blocked by the headlights.

Close-up of the ultrasonic distance sensor

An improvement can be made in our design by incorporating some other way to power the car. Currently, we need to have both Photon 2 boards connected via a wire to an external power source to operate, which means it is greatly limited in where it can travel. Due to time restrictions, we were unable to implement a better power source into our project.

ThingSpeak Integration

An advantage of IOT projects is the ability to integrate Webhooks in order to collect or transfer data. For this project, we were required to set up a Webhook with ThingSpeak in order to graph data. Below you can see the two integrations we created in the Particle Console.

Particle console integrations tab

ThingSpeak channels

Above you can see the two charts created through our ThingSpeak integrations. The data shown in the charts can provide information about the RC car at any time. On the left, you can see the impact status of the car. If the chart reads 1, the car wasn't touching anything, if it reads 0, the car was touching something during that time. On the right, you can see the distance from the sensor to the nearest object in front of the car at various moments in time. All distance data is in inches.

Here is a link to our ThingSpeak channel. Note that it will only update when our Photon 2 boards are active.

Code

// Define the pins for the sensor
const int trigPin = A0;
const int echoPin = D0;

// Variables to store the distance and the publish interval
int distance = 0;
unsigned long lastPublishTime = 0;
const int publishInterval = 1000; // Publish every 1 second

SerialLogHandler logHandler;
int i = 0;

void myHandler(const char *event, const char *data)
{
  i++;
  Log.info("%d: event=%s data=%s", i, event, (data ? data : "NULL"));
}

void setup() {
  // Initialize serial communication
  Serial.begin(9600);

  // Initialize the sensor pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  
  Particle.subscribe("Impact", myHandler);
}

void loop() {
  // Trigger the sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read the echo pin to calculate distance
  long duration = pulseIn(echoPin, HIGH);
  distance = microsecondsToInches(duration);

  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" inches");

  // Publish the distance every publishInterval milliseconds
  if (millis() - lastPublishTime > publishInterval) {
    Particle.publish("distance", String(distance), PRIVATE);
    lastPublishTime = millis();
  }

  // Add a delay to avoid spamming the cloud with too many publishes
  delay(1000);
}

// Function to convert microseconds to inches
long microsecondsToInches(long microseconds) {
  // The speed of sound is 1130 feet per second or 1 foot per 29.1 microseconds
  // The HC-SR04 measures the time it takes for the sound wave to return
  // and converts it to distance using the speed of sound
  return microseconds / 74 / 2;
}

Credits

Tyler Hayes

1 project • 1 follower

Reece Walser

1 project • 1 follower

Upgraded RC Car | MEGR 3171 IoT Project