Week 9 — Input Devices

Group Assignment

Click to access the group assignment

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Motion Detection with PIR Sensor

Assignment Goal

This week's objective was to measure and interpret input signals from a sensor. I chose to use a PIR (Passive Infrared) sensor to detect motion using the XIAO ESP32-C3 board. The sensor outputs a digital HIGH signal when motion is detected and LOW otherwise.

Components Used

• Seeed Studio XIAO ESP32-C3
• PIR Motion Sensor
• Breadboard
• Jumper Wires
• Custom PCB I designed during the previous week

Wiring

PIR Sensor Pin	Connected To
VCC	3.3V (or 5V if sensor requires it)
GND	GND
OUT	D9 (GPIO 9 on XIAO ESP32-C3)

Code

The code reads the digital output of the PIR sensor and prints a message to the serial monitor depending on whether motion is detected.

    #include <Arduino.h>
    
    const int pirPin = 9;  // PIR sensor output connected to GPIO 9
    
    void setup() {
      pinMode(pirPin, INPUT);    // Set PIR pin as input
      Serial.begin(9600);        // Initialize serial communication
    }
    
    void loop() {
      int motionDetected = digitalRead(pirPin); // Read the PIR output
    
      if (motionDetected == HIGH) {
        Serial.println("Motion detected");
      } else {
        Serial.println("No motion");
      }
    
      delay(1000);  // Wait 1 second before the next read
    }
        

Result

When the PIR sensor detects motion, "Motion detected" is printed to the serial monitor. When no motion is present, it prints "No motion". The 1-second delay prevents spamming the serial output and gives the sensor time to stabilize.

Conclusion / What I Learned

This assignment helped me understand how digital input devices like the PIR sensor communicate with microcontrollers. I learned how to configure a digital input pin and interpret its state changes through serial communication. I also gained practical experience in testing and debugging sensor behavior using the serial monitor, which is essential for verifying input device functionality. Furthermore, I explored how PIR sensors detect motion based on infrared radiation and how signal stability can be influenced by timing and sensor characteristics.

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Download Design Files

Here is the Edge_Cuts

Here is the F_Cu

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