How to Use Adafruit MCP9808: Examples, Pinouts, and Specs

The Adafruit MCP9808 (Manufacturer Part ID: 5027) is a high-accuracy digital temperature sensor designed for precision temperature monitoring. It communicates via the I2C interface and provides temperature readings with a resolution of 0.0625°C. The sensor also features an adjustable alert function, allowing users to set temperature thresholds for automated monitoring and control.

• Environmental monitoring systems
• Industrial temperature control
• HVAC systems
• Data logging and weather stations
• IoT devices and smart home applications

The following table outlines the key technical details of the Adafruit MCP9808:

The Adafruit MCP9808 breakout board has the following pin layout:

1. Power the Sensor: Connect the VIN pin to a 3.3V or 5V power source and the GND pin to ground.
2. I2C Communication: Connect the SCL pin to the I2C clock line and the SDA pin to the I2C data line of your microcontroller.
3. Optional Alert Pin: If using the alert function, connect the ALERT pin to a GPIO pin on your microcontroller.

Below is an example of how to connect the MCP9808 to an Arduino UNO:

• VIN → 5V
• GND → GND
• SCL → A5 (Arduino I2C clock line)
• SDA → A4 (Arduino I2C data line)
• ALERT → Optional (connect to a digital pin if needed)

The following Arduino sketch demonstrates how to read temperature data from the MCP9808:

#include <Wire.h>
#include "Adafruit_MCP9808.h"

// Create an MCP9808 object
Adafruit_MCP9808 tempsensor = Adafruit_MCP9808();

void setup() {
  Serial.begin(9600);
  Serial.println("MCP9808 Temperature Sensor Test");

  // Initialize the sensor
  if (!tempsensor.begin(0x18)) { // Default I2C address is 0x18
    Serial.println("Couldn't find MCP9808! Check wiring.");
    while (1);
  }

  // Set resolution to 0.0625°C (highest resolution)
  tempsensor.setResolution(3);
}

void loop() {
  // Read temperature in Celsius
  float tempC = tempsensor.readTempC();

  // Print temperature to the Serial Monitor
  Serial.print("Temperature: ");
  Serial.print(tempC);
  Serial.println(" °C");

  delay(1000); // Wait 1 second before the next reading
}

• Pull-Up Resistors: Ensure that the I2C lines (SCL and SDA) have pull-up resistors (typically 4.7kΩ). Many breakout boards, including the Adafruit MCP9808, include these resistors by default.
• I2C Address: The default I2C address is 0x18, but it can be changed by configuring the address pins (A0, A1, A2) on the breakout board.
• Power Supply: Ensure the power supply voltage matches the sensor's operating range (2.7V to 5.5V).

1. Sensor Not Detected

   • Cause: Incorrect wiring or I2C address mismatch.
   • Solution: Double-check the wiring and ensure the I2C address in the code matches the sensor's configuration.

2. Inaccurate Temperature Readings

   • Cause: External heat sources or poor ventilation around the sensor.
   • Solution: Place the sensor in an environment with stable airflow and away from heat sources.

3. Alert Pin Not Functioning

   • Cause: Alert thresholds not configured correctly.
   • Solution: Use the setAlertTemp() function in the Adafruit MCP9808 library to configure the alert thresholds.

Q: Can the MCP9808 operate at 3.3V?
A: Yes, the MCP9808 operates within a voltage range of 2.7V to 5.5V, making it compatible with both 3.3V and 5V systems.

Q: How do I change the I2C address?
A: The I2C address can be changed by connecting the A0, A1, and A2 pins on the breakout board to VIN or GND. Refer to the Adafruit MCP9808 datasheet for the address configuration table.

Q: What is the maximum I2C clock speed supported?
A: The MCP9808 supports I2C clock speeds up to 400 kHz.

Q: Can I use the MCP9808 for outdoor applications?
A: While the MCP9808 is accurate, it is not weatherproof. For outdoor use, ensure the sensor is housed in a protective enclosure.