SANJIVANI FAB LAB

Sensors are fascinating devices that help machines interact with the physical world. They collect information like distance, motion, temperature, or light and send it to other devices for processing. In this assignment, I studied four different types of sensors: Ultrasonic sensor, PIR sensor, IR sensor, and DHT sensor. Each of these sensors has unique features and applications, making them important in various fields of technology.Before starting this assignment, I had never worked with sensors. However, as I explored each of them, I learned how they work, how to connect them to microcontrollers like Arduino, and how to use them in practical projects. This journey not only helped me understand their functions but also inspired me think about real-world applications where these Sensor are used.

KICAD 9.0 Design

This week, I embarked on an exciting journey of designing my very own custom PCB for the XIAO RP2040. The goal is to create a simple yet functional board with soldering pads to connect a variety of I/O devices, such as sensors, displays, and buttons. My tool of choice for this project - KiCad 9.0, a powerful and open-source PCB design software that I’ve come to appreciate for its flexibility and capability.

With the schematic complete, I moved to the PCB editor to create the physical layout. I placed the components in a way that minimized trace lengths and maintained good signal integrity. The XIAO RP2040 was positioned centrally to allow easy routing of traces to all I/O devices.

After completion of schematic, i m moved to the PCB Routing the traces was an exciting part of the process. I used routing tools to connect the pads on the rp board

I navigated to the File menu in KiCad and selected Fabrication Output. This option allows you to generate all the necessary files for manufacturing the PCB, such as Gerber files, drill files, and more.

Since I wanted to create high-quality vector files to visually represent the PCB layers, I opted for SVG (Scalable Vector Graphics) as the output format.he first layer I plotted was the FCU layer (Front Copper Layer). This layer includes all the traces and pads on the top side of the PCB. Using the Plot function in the Fabrication Output menu, I selected the F.Cu layer and then clicked Plot. KiCad generated the corresponding SVG file for this layer.

The next layer I plotted was the Edge Cut Layer. This layer defines the physical outline of the PCB. It is the boundary that guides the cutting of the PCB board during fabrication. Again, I selected the Edge.Cuts layer from the Fabrication Output options and plotted it separately.

MODS Project

The MODS Project (Modular Open-Source Design Systems) is focused on providing an open-source platform for hardware design, especially for people working on electronics, embedded systems, and custom hardware. The project is geared toward offering modular and customizable tools that help individuals design, build, and prototype electronic systems and devices.

After generation of svg files and moved to free source website for conversion of designed file to machine cutting file MODS Project

I have used the options step by step, as shown in the image for F-Cu SVG file , with the below-mentioned parameters."

After completing the option, I had selected the calcualte option, it will be downloaded the .nc file.

After that i have renamed the .nc to .gcd file to change the machine parameter. In that I have Changed G54 to G55 as per my PCB milling machine

I have used the options step by step, as shown in the image for Edge cut SVG file , with the below-mentioned parameters."

After completing the option, I had selected the calcualte option, it will be downloaded the .nc file.After that i have renamed the .nc to .gcd file to change the machine parameter. In that I have Changed G54 to G55 as per my PCB milling machine

Quiet bit i felt struggled during soldering / desoldering of pins while made a mistake and finally managed with soldering,

Hero shot of my finally completed PCB

Sensors

In this introduction, I will provide an overview of each sensor and explain why they are important.

Ultrasonic Sensor

This sensor measures distance by emitting sound waves and calculating the time it takes for them to bounce back. It is commonly used in parking systems, obstacle detection, and robotics.

PIR Sensor:

A Passive Infrared (PIR) sensor detects motion by sensing heat emitted by living objects. It is widely used in security systems, automatic lighting, and energy-saving devices.

IR Sensor

An Infrared (IR) sensor detects objects or measures distances by using infrared light. It is often used in remote controls, line-following robots, and proximity detection.

DHT Sensor

The DHT sensor measures temperature and humidity, providing critical environmental data. It is used in weather monitoring, smart home systems, and industrial applications.

This assignment has given me a chance to dive into the world of sensors, understand their potential, and explore how they can make machines smarter. The following sections will describe my experience with each sensor in detail, including how I connected them, wrote the code, and tested their functionality.

I have used XIAO RP2040 for the interfacing of input devices and pin diagram i have used for my reference

1. Ultra Sonic Sensor

The HC-SR04 ultrasonic module stands out for its expansive detection range, spanning from 2cm to 400cm , with a remarkable accuracy of up to 3mm. Consequently, it proves to be particularly well-suited for scenarios that demand precise distance measurements.

Pin Details

• VCC supplies power to the HC-SR04 ultrasonic sensor. You can connect it to the 5V output from your Arduino.
• Trig (Trigger) pin is used to trigger ultrasonic sound pulses. By setting this pin to HIGH for 10µs, the sensor initiates an ultrasonic burst.
• Echo pin goes high when the ultrasonic burst is transmitted and remains high until the sensor receives an echo, after which it goes low. By measuring the time the Echo pin stays high, the distance can be calculated.
• GND is the ground pin. Connect it to the ground of the Arduino.

It all starts when the trigger pin is set HIGH for 10µs. In response, the sensor transmits an ultrasonic burst of eight pulses at 40 kHz. This 8-pulse pattern is specially designed so that the receiver can distinguish the transmitted pulses from ambient ultrasonic noise.

These eight ultrasonic pulses travel through the air away from the transmitter. Meanwhile the echo pin goes HIGH to initiate the echo-back signal.

If those pulses are not reflected back, the echo signal times out and goes low after 38ms (38 milliseconds). Thus a pulse of 38ms indicates no obstruction within the range of the sensor.

Calculating the Distance

The width of the received pulse is used to calculate the distance from the reflected object. This can be worked out using the simple distance-speed-time equation we learned in high school. An easy way to remember the equation is to put the letters in a triangle.

Let us take an example to make it more clear. Suppose we have an object in front of the sensor at an unknown distance and we receive a pulse of 500µs width on the echo pin. Now let’s calculate how far the object is from the sensor. For this we will use the below equation.

Distance = Speed x Time

Here we have the value of time i.e. 500 µs and we know the speed. Of course it’s the speed of sound! It is 340 m/s. To calculate the distance we need to convert the speed of sound into cm/µs. It is 0.034 cm/μs. With that information we can now calculate the distance!

Distance = 0.034 cm/µs x 500 µs

Remember that the echo pulse indicates the time it takes for the signal to be sent and reflected back. So to get the distance, you have to divide your result by two.

Distance = (0.034 cm/µs x 500 µs) / 2

Distance = 8.5 cm

Now we know that the object is 8.5 cm away from the sensor.

Connection Diagram

Program Code uploaded using Arduino IDE

#define TRIG_PIN 1  // Trigger pin connected to D2
#define ECHO_PIN 3  // Echo pin connected to D4

void setup() {
  Serial.begin(9600);       // Initialize Serial Monitor
  pinMode(TRIG_PIN, OUTPUT); // Set TRIG_PIN as OUTPUT
  pinMode(ECHO_PIN, INPUT);  // Set ECHO_PIN as INPUT
}

void loop() {
  long duration;
  float distance;

  // Send a 10µs pulse to trigger the sensor
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Measure the duration of the echo
  duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate the distance in centimeters
  distance = (duration * 0.034) / 2;

  // Print the distance
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  delay(500); // Wait 500ms before the next measurement
}

// Pin definition
const int IR_SENSOR_PIN = 2;  // Digital pin connected to the IR sensor

void setup() {
  // Initialize the IR sensor pin as an input
  pinMode(IR_SENSOR_PIN, INPUT);
  
  // Begin serial communication for debugging
  Serial.begin(9600);
  Serial.println("IR Sensor Test Started");
}

void loop() {
  // Read the IR sensor's output
  int sensorValue = digitalRead(IR_SENSOR_PIN);

  // Check if an obstacle is detected
  if (sensorValue == HIGH) {
    Serial.println("Obstacle detected!");
  } else {
    Serial.println("No obstacle.");
  }

  delay(100);  // Small delay for stability
}

 #include "DHT.h"

// Define the DHT11 pin and type
#define DHTPIN 2  // Pin connected to DHT11's DATA pin
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE); // Create a DHT object

void setup() {
  Serial.begin(9600); // Initialize Serial Monitor
  dht.begin();        // Initialize the DHT sensor
  Serial.println("DHT11 Sensor Initialized");
}

void loop() {
  // Wait a bit between sensor readings
  delay(2000);

  // Read temperature and humidity
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  // Check if any readings failed
  if (isnan(humidity) || isnan(temperature)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Print readings to Serial Monitor
  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.print("%  Temperature: ");
  Serial.print(temperature);
  Serial.println("°C");
}

 

const int PIR_SENSOR_PIN = 12;  // PIR sensor output pin
const int LED_PIN = 7;        // LED pin

void setup() {
  pinMode(PIR_SENSOR_PIN, INPUT);  // Set PIR sensor pin as input
  pinMode(LED_PIN, OUTPUT);        // Set LED pin as output
  Serial.begin(9600);             // Initialize serial communication
  Serial.println("PIR Sensor Test Initialized");
}

void loop() {
  int motionDetected = digitalRead(PIR_SENSOR_PIN);  // Read PIR sensor state

  if (motionDetected == HIGH) {
    Serial.println("Motion detected!");
    digitalWrite(LED_PIN, HIGH);  // Turn on LED
  } else {
    digitalWrite(LED_PIN, LOW);   // Turn off LED
  }

  delay(100);  // Small delay for stability
}