lamaPLC: INA226 - current/voltage/power monitor with I²C communication

36V, 16-bit, ultra-precise i²c output current/voltage/power monitor w/alert

The INA226 is a current shunt and power monitor with an I²C or SMBUS-compatible interface. It monitors both a shunt voltage drop and bus supply voltage. Programmable calibration values, conversion times, and averaging, combined with an internal multiplier, enable direct readouts of current in amperes and power in watts.

The INA226 is a current shunt and power monitor with an I²C or SMBUS-compatible interface. The device monitors both a shunt voltage drop and bus supply voltage. Programmable calibration value, conversion times, and averaging, combined with an internal multiplier, enable direct readouts of current in amperes and power in watts. The INA226 senses current on common-mode bus voltages that can vary from 0V to 36V, independent of the supply voltage. The device operates from a 2.7V to 5.5V supply, drawing a typical supply current of 330 μA. The device is specified for an operating temperature range of –40°C to 125°C and features up to 16 programmable addresses via an I2C-compatible interface.

The INA226 supports the fast mode (1 kHz to 400 kHz) and high-speed mode (1 kHz to 2.94 MHz) transmission protocols. All data bytes are transmitted most significant byte first.

• Senses Bus Voltages: 0 V .. 36 V
• Shunt Voltage Maximum: 81.9 V
• Current Maximum: 20 A
• High-Side or Low-Side Sensing
• Reports Current, Voltage, and Power
• High Accuracy:
  • 0.1% Gain Error (Max)
  • 10 μV Offset (Max)
• Configurable Averaging Options
• 16 Programmable Addresses
• Operates from 2.7V to 5.5V Power Supply
• 10-Pin, DGS (VSSOP) Package

The main differences between the INA219 and INA226 lie in their measurement resolution, voltage-handling capabilities, and advanced features. The INA226 is considered the “pro” version for more demanding applications.

Typical Wiring (High-Side Sensing)

• V+ and GND: Connect to your microcontroller's 3.3V or 5V power and ground.
• SDA and SCL: Connect to your microcontroller's I²C pins.
• IN+ and IN-: Place the shunt resistor in series with your load's positive line. Connect IN+ before the resistor and IN- after it.
• VBUS: Connect this pin to IN- (load side) for standard high-side power monitoring.

The Texas Instruments INA226 supports up to 16 unique I²C addresses. The address is set by connecting the two address pins (A0 and A1) to one of four possible points: GND, VS (power supply), SDA, or SCL.

The default address is 0x40 (when both pins are connected to GND).

• VCC/VSS → Arduino 5V (or 3.3V)
• GND → Arduino GND
• SDA → Arduino SDA (A4 on Uno)
• SCL → Arduino SCL (A5 on Uno)

In the Arduino IDE, go to Tools > Manage Libraries, search for “INA226_WE”, and install the version by Wollewald.

This sketch initializes the sensor at the default address (0x40) and prints current, voltage, and power to the Serial Monitor.

#include <Wire.h>
#include <INA226_WE.h>
 
#define I2C_ADDRESS 0x40
 
INA226_WE ina226 = INA226_WE(I2C_ADDRESS);
 
void setup() {
  Serial.begin(9600);
  Wire.begin();
 
  // Initialize INA226
  if (!ina226.init()) {
    Serial.println("Failed to find INA226 chip. Check wiring!");
    while (1);
  }
 
  /* 
     Optional: Calibrate for your shunt. 
     Default is usually 0.1 Ohm. 
     Parameters: (Shunt value in Ohms, Max expected current in Amps)
  */
  ina226.waitUntilConversionCompleted(); 
  Serial.println("INA226 Ready!");
}
 
void loop() {
  float shuntVoltage_mV = 0.0;
  float loadVoltage_V = 0.0;
  float busVoltage_V = 0.0;
  float current_mA = 0.0;
  float power_mW = 0.0;
 
  // Read values
  ina226.readAndClearFlags();
  shuntVoltage_mV = ina226.getShuntVoltage_mV();
  busVoltage_V = ina226.getBusVoltage_V();
  current_mA = ina226.getCurrent_mA();
  power_mW = ina226.getBusPower_mW();
  loadVoltage_V  = busVoltage_V + (shuntVoltage_mV / 1000);
 
  // Print results
  Serial.print("Bus Voltage:   "); Serial.print(busVoltage_V); Serial.println(" V");
  Serial.print("Current:       "); Serial.print(current_mA); Serial.println(" mA");
  Serial.print("Power:         "); Serial.print(power_mW); Serial.println(" mW");
  Serial.println("---------------------------");
 
  delay(2000);
}

https://www.ti.com/product/INA226#tech-docs (Texas Instruments datasheet)

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