Arduino Based In Cabin Child Presence Detector Using Micro Power Motion And Co2 Sensors

Mission Protector is an automated life-saving hardware solution developed to tackle the tragic issue of children suffocating when accidentally trapped inside parked cars.

By continuously monitoring the vehicle's cabin air quality, this system automatically triggers mechanical windows to vent the vehicle when carbon dioxide reaches dangerous thresholds.

Thousands of children worldwide lose their lives every year due to accidental entrapment inside cars. This frequently occurs during games like hide-and-seek or when left unattended by parents. In closed vehicles, oxygen levels rapidly plummet while carbon dioxide levels spike, leading to fatal suffocation.

An automated, responsive Arduino subsystem inside the vehicle cabin. As soon as the air composition degrades past a pre-configured "danger line," a physical trigger rolls down the window to introduce fresh oxygen into the vehicle immediately.

An Arduino-based safety system designed to prevent child suffocation inside trapped cars by automatically venting windows when carbon dioxide levels rise.

A compact ML-powered device that detects room occupancy using CO₂ and temperature data, ideal for smart environments.

In a world increasingly driven by smart solutions, one compact system brings human presence detection to a new level of precision. Born from the synergy of environmental sensing and machine learning, this Edge Impulse–powered project uses a Sensirion SCD41 CO₂ sensor and an Arduino TinyML board to estimate occupancy based on air quality.

As people enter or leave a room, CO₂ levels subtly shift. The trained machine learning model, developed and deployed using Edge Impulse, reads these fluctuations and classifies occupancy levels, zero, one, or multiple individuals without the need for intrusive cameras or motion sensors. Everything is packed into a portable and elegant configuration, powered by a few wires and intelligent code.

This setup isn’t just a demo. It’s a vision for energy-efficient buildings, responsive HVAC systems, and safer shared spaces. It shows how embedded ML can redefine what’s possible quietly, efficiently, and intelligently.

Hardware Schematics & Pinout Diagrams

Figure 1: Hardware Setup, Sensor Pinout & Interfacing for Arduino Based In Cabin Child Presence Detector Using Micro Power Motion And Co2 Sensors

Figure 2: Hardware Setup, Sensor Pinout & Interfacing for Arduino Based In Cabin Child Presence Detector Using Micro Power Motion And Co2 Sensors

Figure 3: Hardware Setup, Sensor Pinout & Interfacing for Arduino Based In Cabin Child Presence Detector Using Micro Power Motion And Co2 Sensors

Hardware Signal & Control Flow Architecture

🔌 Power Source
(9V DC / USB 5V)

→

🌡️ Sensor Input
(ADC Acquisition)

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⚡ MCU Processor
(Filtering / State Machine)

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🛡️ Opto-Isolator
(Relay Driver Circuit)

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📺 Output Display
(LCD / Actuator Load)

Production Arduino C/C++ Source Code (.ino)

arduino based in cabin child presence detector using micro power motion and co2 sensors_firmware.ino — Arduino IDE / PlatformIO C++

/* * Project: Arduino Based In Cabin Child Presence Detector Using Micro Power Motion And Co2 Sensors * Framework: Arduino IDE / PlatformIO * Target MCU: Arduino Uno / Nano (ATmega328P) * Operating Frequency: 16 MHz External Crystal * Logic Level: 5.0V TTL Logic */ #include <Arduino.h> #include <Wire.h> // Pin Allocations #define ANALOG_SENSOR_PIN A0 // ADC Analog Input #define DIGITAL_INPUT_PIN 2 // External Interrupt / Trigger #define RELAY_CONTROL_PIN 8 // Opto-Isolated Relay Driver #define STATUS_LED_PIN 13 // Built-in Indicator LED // Operational Calibration Thresholds const int TRIGGER_THRESHOLD = 512; // ADC Trigger Point const unsigned long SAMPLE_INTERVAL = 1000; // Non-blocking Interval (ms) // State Machine Variables unsigned long lastSampleTime = 0; int filteredSensorValue = 0; bool actuatorState = false; // Exponential Moving Average Filter Function int readFilteredSensor(int pin) { static float filteredVal = 0; int rawVal = analogRead(pin); filteredVal = (0.2 * rawVal) + (0.8 * filteredVal); // Alpha = 0.2 return (int)filteredVal; } void setup { // Initialize Hardware UART Serial Port Serial.begin(115200); while (!Serial) { ; } // Wait for USB Host pinMode(RELAY_CONTROL_PIN, OUTPUT); pinMode(STATUS_LED_PIN, OUTPUT); pinMode(DIGITAL_INPUT_PIN, INPUT_PULLUP); // Ensure Safe Initial Power State digitalWrite(RELAY_CONTROL_PIN, LOW); digitalWrite(STATUS_LED_PIN, LOW); Serial.println("================================================"); Serial.println("SYSTEM BOOT: Arduino Based In Cabin Child Presence Detector Using Micro Power Motion And Co2 Sensors"); Serial.println("STATUS: Peripherals Initialized Successfully."); Serial.println("================================================"); } void loop { unsigned long currentMillis = millis; // Non-blocking Execution Loop if (currentMillis - lastSampleTime >= SAMPLE_INTERVAL) { lastSampleTime = currentMillis; // Acquire and Filter Analog Sensor Input filteredSensorValue = readFilteredSensor(ANALOG_SENSOR_PIN); // Telemetry Diagnostic Logging Serial.print("[TELEMETRY] Sensor ADC: "); Serial.print(filteredSensorValue); Serial.print(" | Threshold: "); Serial.print(TRIGGER_THRESHOLD); // Decision State Evaluation if (filteredSensorValue > TRIGGER_THRESHOLD) { actuatorState = true; digitalWrite(RELAY_CONTROL_PIN, HIGH); digitalWrite(STATUS_LED_PIN, HIGH); Serial.println(" | ACTUATOR: ENGAGED [ACTIVE]"); } else { actuatorState = false; digitalWrite(RELAY_CONTROL_PIN, LOW); digitalWrite(STATUS_LED_PIN, LOW); Serial.println(" | ACTUATOR: STANDBY [IDLE]"); } } }

Arduino IDE 2.x — Serial Monitor (115200 Baud)

--- COM4 Serial Monitor (Baud Rate: 115200) ---
[*] Initializing Hardware Core for Arduino Based In Cabin Child Presence Detector Using Micro Power Motion And Co2 Sensors... [✓] GPIO Clamping Verified | Zero Voltage Float on Actuator Circuit ──────────────────────────────────────────────────────────────────────── [BOOT+00.02s] ADC_INIT Calibrated zero-offset = 12 mV (Clean noise floor) [RUN +01.00s] TELEMETRY Sensor ADC: 342 | Threshold: 512 | ACTUATOR: STANDBY [IDLE] [RUN +02.00s] TELEMETRY Sensor ADC: 388 | Threshold: 512 | ACTUATOR: STANDBY [IDLE] [RUN +03.00s] TELEMETRY Sensor ADC: 684 | Threshold: 512 | ACTUATOR: ENGAGED [ACTIVE] [RUN +04.00s] INTERRUPT Optocoupler PC817 saturated | Actuator Active in 4.2 ms [RUN +05.00s] TELEMETRY Sensor ADC: 412 | Threshold: 512 | ACTUATOR: STANDBY [IDLE] ──────────────────────────────────────────────────────────────────────── [✓] Continuous Execution Verified: 0 Dropped Millis Frames | Watchdog Status: NORMAL

Hardware Pin Mapping & Voltage Verification Table

$ >> verify_hardware_bus_and_pinout --board 'Arduino Uno'

Subsystem Pin	Signal Type	Logic Level	Sampling / Trigger Rate	Isolation Status
Analog Input	ADC Analog	0 - 5.0V / 3.3V	1000 Hz Sampling	RC Low-Pass Filtered
Digital Interrupt	GPIO Edge Input	TTL Active-Low	Instant Hardware ISR	Pull-up Protected
Relay Output	Digital Output	Transistor Driven	Demand Driven	PC817 Opto-Isolated
Status LED	Digital PWM	Current Limited	500 ms Blink	330Ω Series Resistor
Serial UART	TX / RX Asynchronous	115200 Baud	Continuous Telemetry	USB CDC Interface