How to Use INA219: Examples, Pinouts, and Specs

The INA219 is a high-side current shunt and power monitor with an I2C-compatible interface. The device monitors both shunt voltage drop and bus supply voltage, with programmable conversion times and filtering. A precision current-sensing amplifier, an analog-to-digital converter (ADC), and a data acquisition system are integrated into the INA219. It is commonly used in applications such as power management, system protection, battery chargers, and automotive systems.

• Battery monitoring
• Energy management
• Power supply monitoring
• Overcurrent protection systems
• Solar power monitoring

• Voltage Range (Bus): 0 to 26V
• Current Range: -3.2A to +3.2A (with a 0.1 ohm shunt)
• Resolution: 0.8mA with a 0.1 ohm shunt
• I2C Interface: Supports standard (100kHz), fast (400kHz), and high-speed (3.4MHz) modes
• Operating Voltage: 3.0V to 5.5V

1. Connect the Power Supply: Connect Vcc to a 3.0V to 5.5V power supply and GND to the system ground.
2. Shunt Resistor: Connect a shunt resistor between the source of the power and V_IN+ pin, and connect the load to the V_IN- pin.
3. I2C Interface: Connect SDA and SCL to the I2C data and clock lines on your microcontroller.
4. Address Pins: Set the A0 and A1 pins to either GND or Vcc to configure the I2C address of the INA219.

• Ensure that the power supply voltage does not exceed the maximum rating of 5.5V.
• The shunt resistor value determines the maximum current measurement range.
• Use pull-up resistors on the SDA and SCL lines if they are not already present on the microcontroller board.
• Avoid placing the INA219 near high-heat sources to prevent thermal drift in measurements.

#include <Wire.h>
#include <Adafruit_INA219.h>

Adafruit_INA219 ina219;

void setup(void) 
{
  Serial.begin(9600);
  while (!Serial) {
      // Wait for Serial to be ready
  }
  
  uint32_t currentFrequency;
  
  // Initialize the INA219.
  // By default the initialization will use the largest range (32V, 2A).
  if (!ina219.begin()) {
    Serial.println("Failed to find INA219 chip");
    while (1) { delay(10); }
  }
  // To use a slightly lower 32V, 1A range (higher precision on amps):
  // ina219.setCalibration_32V_1A();
  // Or to use a lower 16V, 400mA range (higher precision on volts and amps):
  // ina219.setCalibration_16V_400mA();

  Serial.println("Measuring voltage and current with INA219 ...");
}

void loop(void) 
{
  float shuntvoltage = 0;
  float busvoltage = 0;
  float current_mA = 0;
  float loadvoltage = 0;

  shuntvoltage = ina219.getShuntVoltage_mV();
  busvoltage = ina219.getBusVoltage_V();
  current_mA = ina219.getCurrent_mA();
  loadvoltage = busvoltage + (shuntvoltage / 1000);
  
  Serial.print("Bus Voltage:   "); Serial.print(busvoltage); Serial.println(" V");
  Serial.print("Shunt Voltage: "); Serial.print(shuntvoltage); Serial.println(" mV");
  Serial.print("Load Voltage:  "); Serial.print(loadvoltage); Serial.println(" V");
  Serial.print("Current:       "); Serial.print(current_mA); Serial.println(" mA");
  Serial.println("");

  delay(2000);
}

• Inaccurate Readings: Ensure that the shunt resistor is properly rated for the current you are measuring.
• No Data on I2C: Check the connections and ensure that the correct I2C address is being used.
• Overcurrent Situation: If the current exceeds the maximum rating, the INA219 may not provide accurate readings.

• Double-check wiring, especially the connections to the shunt resistor.
• Verify that the INA219 is properly powered and that the voltage does not exceed 5.5V.
• Use the Wire library's beginTransmission() and endTransmission() functions to check for I2C communication issues.

Q: Can the INA219 measure both AC and DC currents? A: The INA219 is designed to measure DC currents only.

Q: What is the maximum voltage that can be measured? A: The INA219 can measure bus voltages up to 26V.

Q: How do I change the I2C address of the INA219? A: The I2C address can be changed by connecting the A0 and A1 pins to either GND or Vcc. The datasheet provides a table of the address configurations.

Q: Is it necessary to calibrate the INA219? A: The INA219 comes pre-calibrated, but you can adjust the calibration settings to match the shunt resistor and expected current range for higher accuracy.

Q: Can the INA219 be used with a microcontroller other than an Arduino? A: Yes, the INA219 can be interfaced with any microcontroller that supports I2C communication. Adjustments to the code may be necessary to accommodate different platforms.