Tiny Power Meter V2 is a compact and practical power measurement device designed to work with XT60 connectors. It allows users to easily measure voltage, current, and power consumption by simply connecting a power source to the input and a load to the output. All values are displayed in real time on a small OLED screen, making it ideal for electronics testing, battery analysis, and FPV drone applications. The project focuses on simplicity, accuracy, and portability while maintaining a clean and professional hardware design.

How It Works

The power meter is built around the Seeed Studio XIAO ESP32-C3, paired with the INA226 high-precision current and power monitoring IC. The INA226 measures the voltage drop across a low-value shunt resistor to calculate current and simultaneously measures the bus voltage. Using these parameters, it computes real-time power consumption. Communication between the INA226, OLED display, and XIAO ESP32-C3 is handled through the I²C bus, keeping the circuit efficient and minimal. The entire system is powered directly from the input voltage, with XT60 connectors used for both input and output.

Key Features

1. Current measurement up to ±10 A
2. Bus voltage sensing from 5 V to 36 V
3. Compact and portable inline power meter
4. XT60 connectors for reliable high-current connections
5. Real-time display of voltage, current, and wattage

INA226 Current Sensor Explained

The INA226 is a high-accuracy current, voltage, and power monitoring IC that communicates over I²C. It measures the differential voltage across a shunt resistor to calculate current and also monitors the bus voltage to compute power in real time.

The current is calculated using the formula:

Current (I) = Shunt Voltage (Vshunt) / Shunt Resistance (Rshunt)

With a 0.005 Ω shunt resistor and the INA226’s ±81.92 mV full-scale shunt voltage range:

Maximum Current (Imax) = 81.92 mV / 0.005 Ω

Maximum Current (Imax) ≈ 16.38 A

This means the maximum measurable current using this shunt resistor is approximately 16.38 A.

PCB Design

The PCB design is kept compact due to the minimal external components required by the INA226. The schematic and PCB were designed using EasyEDA, and all necessary build files are attached for reference. XT60 connectors are used for both input and output, allowing the power meter to be connected inline without modifying existing setups.

Enclosure Design

The enclosure was designed in Autodesk Fusion 360. The PCB STEP file was imported for accurate fitting and alignment. The enclosure uses a two-part design with a minimum wall thickness of 0.8 mm and is secured using four M3 × 10 mm screws.

Firmware & Calibration

The firmware is written using the Arduino framework and utilizes:

1. Adafruit_INA226 library
2. Adafruit_SSD1306 library

Calibration is performed using:

ina226.setCalibration(0.005, 10.0);

First parameter: Shunt resistor value (5 mΩ)

Second parameter: Maximum expected current (Amps)

This value can be adjusted based on the application requirements.

Assembly & Testing

Assembly begins by soldering components according to the schematic. It is recommended to program the XIAO ESP32-C3 before soldering it to the PCB. The OLED display should be mounted carefully to align with the enclosure window. For testing, connect the power source to the XT60 input and the load to the XT60 output. The OLED will immediately display voltage, current, and power readings. XT60 connectors also make it easy to create custom adapters, such as DC jack to XT60 cables, which is especially useful for FPV drone and battery testing applications.

Credit & Acknowledgement

This project is shared for educational and community reference purposes only.

Complete Design & Engineering Credit: Gokul

Community Shared By: Bholu

All technical design, planning, and implementation belong to the original creator. This article is shared to respectfully acknowledge and highlight the work within the PCBWay community, encouraging learning and collaboration.