1.10 Motion Detection
=========================
A PIR (Passive Infrared) sensor is like an electronic "heat vision" detector! It doesn't emit anything - instead, it "watches" for changes in infrared heat patterns. When a warm object (like a person or pet) moves through its field of view, it detects the heat signature change and triggers an alert.

You'll find PIR sensors in automatic lights, security systems, and smart home devices. They're perfect for detecting "something moved" rather than "something is there."

Component List
^^^^^^^^^^^^^^^
- Raspberry Pi Pico W x1
- MicroUSB cable x1
- 830 Tie-Points Breadboard x1
- Jumper Wire Several
- PIR Motion Sensor Module x1

Component knowledge
^^^^^^^^^^^^^^^^^^^^
:ref:`PIR Motion Sensor Module <cpn_pir_module>`
"""""""""""""""""""""""""""""""""""""""""""""""""

How motion detection works:
- **No movement**: PIR sees steady heat pattern → GP14 reads **LOW** (0V)
- **Motion detected**: PIR detects heat change → GP14 reads **HIGH** (3.3V)

The PIR module has **built-in processing** - it only triggers when it detects a change in heat patterns, not just the presence of warm objects.

.. note:: 
    The PIR module has two potentiometers: one adjusts sensitivity, the other 
    adjusts detection distance. To make the PIR module work better, you need to 
    turn both of them counterclockwise to the end.

.. image:: img/6.other/PIR2.png

Connect
^^^^^^^^^
.. image:: img/3.connect/1.10.png

Code
^^^^^^^
.. note::

    * Open the ``1.10_motion_detection.ino`` file under the path of ``Ultimate-Starter-Kit-for-Pico-W\Arduino\1.Project`` or copy this code into Thonny, then click "Run Current Script" or simply press F5 to run it.

    * Or copy this code into Arduino IDE.

    * Don’t forget to select the board(Raspberry Pi Pico) and the correct port before clicking the Upload button. 

.. 1.10.png

After running the code, wave your hand or walk in front of the PIR sensor. You'll see "MOTION DETECTED!" alerts with detection counters, timestamps, and status updates. The system will also tell you when motion stops and the area is clear again.

The following is the program code:

.. code-block:: c++

    /*
      Motion Detection Alert System

      Uses a PIR sensor to detect motion and provides 
      alert messages with detection counting.
    */

    // Pin definition and constants
    const int PIR_SENSOR_PIN = 14;      // PIR sensor connected to pin 14
    const int DETECTION_DELAY = 200;    // delay between readings in milliseconds

    // Variables for motion tracking
    bool motionDetected = false;        // current motion state
    bool lastMotionState = false;       // previous state for change detection
    int detectionCount = 0;             // total number of detections
    unsigned long lastDetectionTime = 0; // timestamp of last detection

    void setup() {
      // Configure PIR sensor pin as input
      pinMode(PIR_SENSOR_PIN, INPUT);
      
      // Initialize serial communication
      Serial.begin(115200);
      
      // Display system startup message
      showStartupMessage();
    }

    void loop() {
      // Check for motion detection
      checkMotionSensor();
      
      // Wait before next reading
      delay(DETECTION_DELAY);
    }

    // Function to display startup information
    void showStartupMessage() {
      Serial.println("=== Motion Detection System ===");
      Serial.println("PIR sensor monitoring active");
      Serial.println("Waiting for motion...");
      Serial.println("==============================");
      Serial.println();
    }

    // Function to monitor PIR sensor and detect motion changes
    void checkMotionSensor() {
      // Read current PIR sensor state
      motionDetected = digitalRead(PIR_SENSOR_PIN);
      
      // Check if motion was just detected (state change from no motion to motion)
      if (motionDetected && !lastMotionState) {
        // Record detection time and increment counter
        lastDetectionTime = millis();
        detectionCount++;
        
        // Trigger motion alert
        triggerMotionAlert();
      }
      
      // Check if motion stopped (state change from motion to no motion)
      if (!motionDetected && lastMotionState) {
        Serial.println("Motion stopped - area clear");
        Serial.println();
      }
      
      // Update last state for next comparison
      lastMotionState = motionDetected;
    }

    // Function to handle motion detection alert
    void triggerMotionAlert() {
      Serial.println(">>> MOTION DETECTED! <<<");
      Serial.println("Alert: Movement in monitored area");
      
      // Show detection statistics
      Serial.print("Detection #");
      Serial.println(detectionCount);
      
      Serial.print("Time: ");
      Serial.print(lastDetectionTime);
      Serial.println(" ms");
      
      Serial.println("Status: ACTIVE");
      Serial.println();
    }

Phenomenon
^^^^^^^^^^^
.. image:: img/5.phenomenon/1.10.png
    :width: 100%