IoT Cold Storage Humidity And Ethylene Scrubber Controller For Post Harvest Fruit Preservation

This project presents an IoT-enabled smart fruit storage system that automates the control of temperature, humidity, and air quality using embedded sensors and actuators. The system is built using an Arduino Mega for local control and an ESP8266 module for cloud integration via the Arduino IoT Cloud platform.

It is designed to reduce spoilage and maintain optimal storage conditions through environmental sensing, actuator control, and remote monitoring.

Sensor data and actuator states are transmitted from Arduino Mega to the ESP8266 via Serial1. The ESP8266 publishes this data to the Arduino IoT Cloud, where it is visualized and monitored in real time. Manual override switches are also integrated, allowing remote control of actuators such as the Peltier module and ventilation fan.

Explanation: https://youtu.be/SsQY30of0jE Final Presentation: https://youtu.be/XsfrfsZgzEw

IoT-based Smart Fruit Storage System developed for EEE 416 at BUET. Monitors temperature, humidity, and air quality using DHT22 and MQ135 sensors. Controls mist, Peltier cooling, and ventilation via relays. Arduino Mega handles local automation; ESP8266 enables real-time monitoring and control through Arduino IOT Cloud

This is an IOT project, help to control temperature & humidity in a Cold Storage via the internet. Depend on the kind of storage (i.e. fruits, vaccine, food... ), the device can auto maintain temperature & humidity base on the pre-configuration.

Sensor's metrics will be collected by 8051 and saved on EEPROM, 8051 also control the Cooling Fan & Humidifier Machine on or off.

ESP8266 will help to connect to internet (Thingsboard), transmit data between 8051 & Thingsboard

The metrics of Temperature & humidity will keeping sync-up from DHT11 sensor to Thingsboard.

Mode Auto: User can config the proper thresholds and the 8051 will auto maintain temperature/humdity by control Cooling Fan/Humidifier Machine.

Comunicate with ESP8266 using protocol Message Queueing Telemetry Transport (MQTT) - Remote Procedure Calls (RPC) API. Service provider: Thingsboard's message broker

There is a schedule from Thingsboard that send an RCP request to update telemetry, this will keep the metrics up-to-date every 20 seconds.

Hardware Schematics & Pinout Diagrams

Figure 1: Hardware Setup, Sensor Pinout & Interfacing for IoT Cold Storage Humidity And Ethylene Scrubber Controller For Post Harvest Fruit Preservation

Figure 2: Hardware Setup, Sensor Pinout & Interfacing for IoT Cold Storage Humidity And Ethylene Scrubber Controller For Post Harvest Fruit Preservation

Figure 3: Hardware Setup, Sensor Pinout & Interfacing for IoT Cold Storage Humidity And Ethylene Scrubber Controller For Post Harvest Fruit Preservation

Hardware Signal & Control Flow Architecture

🔌 Power Source
(9V DC / USB 5V)

→

🌡️ Sensor Input
(ADC Acquisition)

→

⚡ MCU Processor
(Filtering / State Machine)

→

🛡️ Opto-Isolator
(Relay Driver Circuit)

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📺 Output Display
(LCD / Actuator Load)

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

iot cold storage humidity and ethylene scrubber controller for post harvest fruit preservation_firmware.ino — Arduino IDE / PlatformIO C++

/* * Project: IoT Cold Storage Humidity And Ethylene Scrubber Controller For Post Harvest Fruit Preservation * 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: IoT Cold Storage Humidity And Ethylene Scrubber Controller For Post Harvest Fruit Preservation"); 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 IoT Cold Storage Humidity And Ethylene Scrubber Controller For Post Harvest Fruit Preservation... [✓] 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