Smart Temperature Control System for Refrigerators - Electronic Engineering Guide
1. Introduction
A Smart Temperature Control System for Refrigerators ensures optimal cooling by monitoring internal temperature and dynamically adjusting compressor operation. This system increases energy efficiency, prolongs compressor life, and enhances food preservation.
2. Objectives
• To automatically regulate refrigerator temperature.
• To implement real-time temperature sensing.
• To reduce energy consumption through smart control.
• To provide user feedback on temperature status.
3. Components Required
• Arduino Uno / ESP32 / NodeMCU
• Temperature Sensor (DS18B20 / LM35 / DHT22)
• Relay Module
• LCD Display (16x2) or OLED
• Push Buttons (for setting thresholds)
• Buzzer (optional)
• Power Supply (5V DC)
• Resistors, jumper wires, PCB/breadboard
4. System Overview
The system constantly monitors the internal temperature of the refrigerator. When temperature exceeds or falls below preset limits, it activates or deactivates the compressor via a relay. User-defined settings allow adjustment of temperature thresholds.
5. Temperature Sensing and Control Logic
• The sensor reads real-time temperature inside the fridge.
• The controller compares it to upper and lower thresholds.
• If temperature exceeds upper threshold → compressor ON.
• If it falls below lower threshold → compressor OFF.
6. Microcontroller Integration
• Connect sensor output to analog/digital pin of
microcontroller.
• Relay module controls power to the compressor circuit.
• LCD/OLED provides live temperature feedback and settings display.
• Push buttons adjust threshold temperatures stored in EEPROM.
7. User Interface and Feedback
• LCD displays current temperature and setpoints.
• Buttons allow user to increase/decrease threshold settings.
• Optional buzzer alerts on over-temperature condition.
8. Circuit Diagram and Working
• Connect DS18B20 to digital pin with pull-up resistor
(4.7kΩ).
• Relay module connected to digital pin to switch compressor power.
• LCD/OLED connected via I2C or parallel pins.
• Buttons pulled-down to ground with pull-up logic in code.
9. Software and Code Explanation
Sample Arduino Code Snippet:
#include <OneWire.h>
#include <DallasTemperature.h>
#define ONE_WIRE_BUS 2
#define RELAY 3
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
float upperLimit = 8.0;
float lowerLimit = 3.0;
void setup() {
pinMode(RELAY, OUTPUT);
sensors.begin();
Serial.begin(9600);
}
void loop() {
sensors.requestTemperatures();
float tempC =
sensors.getTempCByIndex(0);
Serial.print("Temp: ");
Serial.println(tempC);
if (tempC > upperLimit)
digitalWrite(RELAY, HIGH);
else if (tempC < lowerLimit)
digitalWrite(RELAY, LOW);
delay(2000);
}
10. Applications
• Smart refrigerators
• Cold storage and transport
• Medical refrigeration systems
• Food preservation monitoring
11. Challenges and Enhancements
• Accurate calibration of sensors is essential.
• Incorporate hysteresis to avoid relay chattering.
• Use NTC thermistors for lower-cost solutions.
• Integrate IoT for remote monitoring and alerts.
12. Conclusion
A Smart Temperature Control System for Refrigerators enhances energy efficiency, food safety, and user experience. This guide provides a foundation for building and expanding intelligent temperature control solutions in embedded systems.