How to Use INA226: Examples, Pinouts, and Specs

The INA226, manufactured by Sensor, is a high-side current shunt monitor with an integrated I2C interface. It is designed to measure both current and voltage with high precision, thanks to its built-in analog-to-digital converter (ADC). The INA226 is widely used in power monitoring applications, offering a versatile solution for tracking energy consumption in electronic devices.

• Power monitoring in servers, computers, and networking equipment
• Battery management systems
• Solar inverters and renewable energy systems
• Industrial automation and motor control
• Consumer electronics requiring precise power measurement

The INA226 is a robust and versatile component with the following key specifications:

The INA226 is available in a small package with the following pinout:

The INA226 is straightforward to use in a circuit, but proper configuration and calibration are essential for accurate measurements.

1. Power Supply: Connect the V_CC pin to a 3.3V or 5V power source, and the GND pin to the ground.
2. Shunt Resistor: Place a precision shunt resistor between the load and the ground. Connect the V_IN+ and V_IN- pins across the shunt resistor.
3. I2C Interface: Connect the SCL and SDA pins to the corresponding I2C lines of your microcontroller. Use pull-up resistors (typically 4.7 kΩ) on these lines.
4. Address Configuration: Set the I2C address by connecting the ADDR pin to GND, V_CC, or leaving it floating (refer to the datasheet for address mapping).
5. Alert Pin (Optional): Use the ALERT pin to monitor threshold events, such as overcurrent or undervoltage conditions.

The INA226 can be easily interfaced with an Arduino UNO using the Wire library. Below is an example code snippet to read voltage and current:

#include <Wire.h>

// INA226 I2C address (default: 0x40)
#define INA226_ADDRESS 0x40

// Register addresses
#define REG_BUS_VOLTAGE 0x02
#define REG_CURRENT     0x04

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

  // Configure INA226 (e.g., calibration, averaging, etc.)
  configureINA226();
}

void loop() {
  float busVoltage = readBusVoltage(); // Read bus voltage in volts
  float current = readCurrent();       // Read current in amps

  // Print the results to the serial monitor
  Serial.print("Bus Voltage: ");
  Serial.print(busVoltage);
  Serial.println(" V");

  Serial.print("Current: ");
  Serial.print(current);
  Serial.println(" A");

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

void configureINA226() {
  // Example: Write calibration value to the INA226
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(0x05); // Calibration register address
  Wire.write(0x10); // High byte of calibration value
  Wire.write(0x00); // Low byte of calibration value
  Wire.endTransmission();
}

float readBusVoltage() {
  uint16_t rawValue = readRegister(REG_BUS_VOLTAGE);
  return rawValue * 0.00125; // Convert to volts (1.25 mV per LSB)
}

float readCurrent() {
  uint16_t rawValue = readRegister(REG_CURRENT);
  return rawValue * 0.001; // Convert to amps (example scaling factor)
}

uint16_t readRegister(uint8_t reg) {
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(reg); // Specify the register to read
  Wire.endTransmission();

  Wire.requestFrom(INA226_ADDRESS, 2); // Request 2 bytes
  uint16_t value = (Wire.read() << 8) | Wire.read(); // Combine MSB and LSB
  return value;
}

• Shunt Resistor Selection: Choose a shunt resistor with a low temperature coefficient and appropriate resistance to ensure accurate current measurements.
• Calibration: Properly calibrate the INA226 for your specific shunt resistor to achieve precise results.
• I2C Pull-Up Resistors: Ensure the I2C lines have appropriate pull-up resistors to maintain reliable communication.
• Voltage Range: Do not exceed the maximum input voltage of 36V to avoid damaging the device.

1. No I2C Communication:

   • Ensure the SCL and SDA lines are connected correctly and have pull-up resistors.
   • Verify the I2C address matches the configuration of the ADDR pin.

2. Incorrect Voltage or Current Readings:

   • Check the shunt resistor value and ensure it matches the calibration settings.
   • Verify the connections to the V_IN+ and V_IN- pins.

3. Alert Pin Not Functioning:

   • Confirm that the alert thresholds are correctly configured in the INA226 registers.
   • Check the connection to the ALERT pin.

• Use an I2C scanner sketch to verify the INA226 is detected on the I2C bus.
• Double-check all wiring and connections for loose or incorrect placements.
• Refer to the INA226 datasheet for detailed register descriptions and configuration options.

By following this documentation, you can effectively integrate the INA226 into your projects for precise power monitoring and management.