How to Use MAX30205 Human Body Temp Sensor: Examples, Pinouts, and Specs

The MAX30205 is a high-accuracy digital temperature sensor specifically designed for measuring human body temperature. It provides precise temperature readings with a resolution of 16 bits and outputs the data digitally via an I²C interface. The sensor operates with low power consumption, making it ideal for battery-powered devices. Its compact design and high precision make it a popular choice for wearable devices, medical monitoring systems, and other health-related applications.

• Wearable health monitoring devices
• Medical thermometers
• Fitness trackers
• Patient monitoring systems
• IoT health applications

The MAX30205 offers the following key technical features:

The MAX30205 comes in an 8-pin TDFN package. Below is the pinout and description:

1. Power Supply: Connect the VDD pin to a 3.3V power source and the GND pin to ground.
2. I²C Communication: Connect the SDA and SCL pins to the corresponding I²C lines of your microcontroller. Use pull-up resistors (typically 4.7kΩ) on both lines.
3. Alert Pin (Optional): The ALERT pin can be used to trigger an interrupt on the microcontroller when the temperature exceeds a user-defined threshold. If unused, leave it unconnected.
4. Bypass Capacitor: Place a 0.1µF ceramic capacitor close to the VDD pin to stabilize the power supply.

• The MAX30205 is optimized for body temperature measurement. Ensure the sensor is in direct contact with the skin for accurate readings.
• Avoid exposing the sensor to temperatures outside its operating range (+10°C to +50°C) to maintain accuracy.
• Use proper I²C pull-up resistors to ensure reliable communication.
• Minimize noise in the circuit by keeping the I²C lines short and using a ground plane.

Below is an example of how to interface the MAX30205 with an Arduino UNO using the Wire library:

#include <Wire.h>

#define MAX30205_ADDRESS 0x48  // I²C address of the MAX30205

void setup() {
  Wire.begin();  // Initialize I²C communication
  Serial.begin(9600);  // Start serial communication for debugging

  // Configure the MAX30205 (optional: default settings are usually sufficient)
  Wire.beginTransmission(MAX30205_ADDRESS);
  Wire.write(0x01);  // Point to configuration register
  Wire.write(0x00);  // Set configuration to default (continuous conversion)
  Wire.endTransmission();
}

void loop() {
  float temperature = readTemperature();
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");
  delay(1000);  // Wait 1 second before the next reading
}

float readTemperature() {
  Wire.beginTransmission(MAX30205_ADDRESS);
  Wire.write(0x00);  // Point to temperature register
  Wire.endTransmission();

  Wire.requestFrom(MAX30205_ADDRESS, 2);  // Request 2 bytes of data
  if (Wire.available() == 2) {
    uint8_t msb = Wire.read();  // Most significant byte
    uint8_t lsb = Wire.read();  // Least significant byte
    int16_t rawTemp = (msb << 8) | lsb;  // Combine bytes into a 16-bit value
    return rawTemp * 0.00390625;  // Convert to Celsius (16-bit resolution)
  }
  return -999.0;  // Return error value if data is unavailable
}

• The I²C address of the MAX30205 is 0x48 by default. Verify this in your setup.
• The temperature is calculated by multiplying the raw 16-bit value by 0.00390625 (1/256), as per the sensor's datasheet.

1. No Temperature Reading:

   • Ensure the sensor is powered correctly (VDD = 3.3V, GND connected).
   • Verify the I²C connections (SDA and SCL) and check for proper pull-up resistors.
   • Confirm the I²C address (0x48) matches the sensor's default address.

2. Inaccurate Temperature Readings:

   • Ensure the sensor is in direct contact with the skin for accurate body temperature measurement.
   • Avoid placing the sensor near heat sources or in areas with high airflow.

3. I²C Communication Errors:

   • Check the pull-up resistor values (4.7kΩ is typical).
   • Ensure the I²C clock speed does not exceed 400kHz.

Q: Can the MAX30205 measure ambient temperature?
A: While the MAX30205 is optimized for body temperature measurement, it can measure ambient temperatures within its operating range (+10°C to +50°C). However, accuracy may be reduced outside the +30°C to +40°C range.

Q: What is the ALERT pin used for?
A: The ALERT pin is an open-drain output that goes low when the temperature exceeds a user-defined threshold. It can be used to trigger interrupts or alarms in your system.

Q: Can I use the MAX30205 with a 5V microcontroller?
A: Yes, but you must use level shifters for the I²C lines (SDA and SCL) since the MAX30205 operates at 3.3V logic levels.

Q: How do I improve measurement accuracy?
A: Ensure the sensor is properly calibrated, minimize noise in the circuit, and maintain good thermal contact with the measurement surface.