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Projects/Electronics/Building an I2C Temperature Controller.md

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+---
+active: false
+tags: project
+created: 2026-05-28 15:23
+---
+## Summary
+
+Building an I2C temperature controller involves reading temperature from an I2C sensor (like an MCP9808 or DHT12) and using an Arduino to trigger a relay (for heaters/coolers) or adjust a fan.  Use the standard `<Wire.h>` library for communication and control relays based on your temperature thresholds. 
+
+Here is a straightforward guide to get your project running.
+
+🛠️ Hardware Requirements
+
+- **Microcontroller:** Arduino Uno or Nano
+- **I2C Temperature Sensor:** MCP9808 (High precision) or DHT12
+- **I2C Display (Optional):** 16x2 LCD with I2C backpack (PCF8574)
+- **Control Element:** 5V Relay module (to switch a fan or heater)
+- **Misc:** Breadboard, jumper wires, and 4.7kΩ pull-up resistors (if not built into your sensor modules) 
+
+🔌 Wiring the Components
+
+Connect your I2C devices to the Arduino's I2C bus. You will share these lines between the sensor and the display.
+
+- **VCC**  Arduino 
+- **GND**  Arduino 
+- **SDA** Arduino Analog Pin (or the dedicated pin on newer boards)
+- **SCL** Arduino Analog Pin (or the dedicated pin on newer boards)
+- **Relay Signal Pin** Arduino Digital Pin 
+
+Before running this code, ensure you have installed the **Adafruit MCP9808 Library** and the **LiquidCrystal_I2C Library** via the Arduino IDE Library Manager (`Sketch > Include Library > Manage Libraries`).
+
+```
+#include <Wire.h>
+#include <Adafruit_MCP9808.h>
+#include <LiquidCrystal_I2C.h>
+
+// Create sensor and display objects
+Adafruit_MCP9808 tempsensor = Adafruit_MCP9808();
+LiquidCrystal_I2C lcd(0x27, 16, 2); // Set the LCD address to 0x27 for a 16 chars and 2 line display
+
+const int RELAY_PIN = 7;
+const float TARGET_TEMP = 25.0; // Target temperature in Celsius
+const float HYSTERESIS = 0.5;   // Prevents relay rapid switching (chattering)
+
+void setup() {
+  Serial.begin(9600);
+  pinMode(RELAY_PIN, OUTPUT);
+  digitalWrite(RELAY_PIN, HIGH); // Default to OFF (Relays are often active LOW)
+
+  // Initialize I2C LCD
+  lcd.init();                      
+  lcd.backlight();
+  lcd.setCursor(0, 0);
+  lcd.print("I2C Temp Ctrl");
+
+  // Initialize sensor
+  if (!tempsensor.begin(0x18)) { // Default I2C address for MCP9808
+    Serial.println("Couldn't find MCP9808!");
+    while (1);
+  }
+  tempsensor.setResolution(3); // Set resolution to 0.0625°C
+}
+
+void loop() {
+  tempsensor.wake();   // Wake up sensor
+  float tempC = tempsensor.readTempC();
+  tempsensor.shutdown(); // Shutdown to save power/reduce self-heating
+
+  // Update Display
+  lcd.setCursor(0, 1);
+  lcd.print("Temp: ");
+  lcd.print(tempC);
+  lcd.print("C");
+
+  // Temperature Control Logic
+  if (tempC > (TARGET_TEMP + HYSTERESIS)) {
+    digitalWrite(RELAY_PIN, LOW); // Turn ON cooling/heating
+  } 
+  else if (tempC < (TARGET_TEMP - HYSTERESIS)) {
+    digitalWrite(RELAY_PIN, HIGH); // Turn OFF cooling/heating
+  }
+
+  delay(1000); // Read temperature every second
+}
+```
+
+
+## Tasks
+
+
+## References