Build a DC Energy Meter using Arduino – 32V/5A

Overview

In this project, we will build a DC Energy Meter using Arduino that can measure voltage, current, power, and energy consumption.

I recently came across a neat custom-made DC energy meter module from Mutex Embedded. This small but powerful board can measure DC parameters such as voltage (0–32 V range), current (up to 5 A), power, and cumulative energy consumption. It communicates easily over the I²C protocol, making it ideal for direct use with Arduino.

For this guide, I’ll show you how to connect the module to an Arduino and display the live energy meter data on a 16×2 I²C LCD display. The LCD cycles through values of voltage, current, power, and energy, so you can view the parameters in real time without needing a computer.

If you want to take it further, the same module also includes an ESP32 chip option for IoT applications, where the readings can be uploaded to a web server for remote monitoring. But in this guide, we’ll focus only on the Arduino + LCD setup. This project is a simple yet very practical way to track DC energy usage for your electronics, battery projects, or renewable energy experiments. You may use the same DC power module to make an IoT DC Energy meter with ESP32 and view the live data on Webserver.

Bill of Materials

We need following components to build this Arduino DC Energy Meter project.

DC Power Monitor Module

The DC Power Monitoring Module is a feature-rich solution for tracking voltage, current, power, and energy consumption across four independent channels. At its core is the ESP32-S2 microcontroller, ensuring high performance and IoT readiness. Current measurement is handled through precision high-wattage shunt resistors, while an onboard SD card slot enables real-time data logging. A CR1220 coin cell holder powers the real-time clock, allowing accurate time-stamping of measurements even when the main supply is off.

On the hardware side, the board includes a tiny rear connector that works with a dedicated power extension board, which provides a USB-to-serial interface, micro-USB port, and reset switch. With support for up to 32 V input voltage and 5 A current per channel, the module is well-suited for monitoring small to medium DC appliances or battery systems.

The module supports both I²C and Modbus RTU (UART/RS485) interfaces, making it compatible with a wide range of microcontrollers, including Arduino and ESP32. Data can also be logged to the SD card for up to a year, with weekly historical summaries available for long-term analysis. To simplify user experience, a free PC application is provided for configuration, live monitoring, and firmware updates.

Features & Specifications

• Voltage range: 0 – 32V
• Current range 0 – 5A
• 4 – Channels with common GND
• Serial Interface: I2C + UART Modbus
• RS-485 Bus extension
• Real-Time Clock
• Micro SD Card Data Logging
• PC Application
• Built for Industrial use

Useful Links

1. DC Power Monitor Module
2. DC Power Monitor Extension
3. Datasheet/User Manual
4. PC Application Software

Interfacing the DC Energy Meter with Arduino

The DC Power Monitor Module supports both I²C and Modbus RTU communication protocols. In this project, we will be using the I²C interface to connect the module with an Arduino and build our own DC Energy Meter.

Hardware & Circuit

The wiring is very straightforward. Connect the VCC pin of the Power Monitor Module to the 3.3V pin on the Arduino, and connect the GND pin to the Arduino GND. Then, link the communication lines by connecting the module’s SDA pin to the Arduino’s A4 pin and the SCL pin to the Arduino’s A5 pin.

With just these four simple connections, the Arduino will be able to read voltage, current, power, and energy data directly from the module over the I²C bus.

Power Supply & Load Connection

To begin, we need to connect a DC supply and a load to the Power Monitor Module. The board provides four input/output channels labeled IN1–IN4 and OUT1–OUT4. In this example, we will be using Channel 1.

• Connect the Supply
  Take any DC supply, such as a battery or a regulated DC adapter. Connect the positive terminal of the supply to the IN1 terminal. The negative (ground) terminal of the supply should be connected to the GND line provided on the module.
• Connect the Load
  For the load connection, wire the positive terminal of your load (e.g., a DC motor, lamp, or electronic circuit) to the OUT1 terminal. The negative terminal of the load should also be connected to the common GND of the module.

That’s all that is needed—the module will now measure the supply voltage, the current flowing through the load, and automatically calculate power and energy consumption for Channel 1.

I2C Library (MbI2C_ArduinoPort.h)

The developer of this product has already created a library for the DC Power Monitor Module. Although it was originally written for another microcontroller, I have adapted the same library and used it in this Arduino project to read data via the I²C interface.

Create a folder anywhere in your computer and name it as “mb_energy_meter“. Inside the folder create a text file and save it as “MbI2C_ArduinoPort.h“. Copy the following library code and paste it in the .h file and save it.

Source Code/Program (DC Energy Meter using Arduino)

This Arduino sketch communicates with the DC Power Monitor Module over the I²C bus and continuously reads voltage, current, power, and total energy from Channel 1. It converts the raw register data into real-world units and prints the measurements to the Serial Monitor every 500 ms. It also performs an optional firmware version check during setup.

Create a new file on the folder that you created earlier and save it with a name “mb_energy_meter.ino“. Paste the following code on the ino file. Then open the Arduino code.

Testing the Arduino DC Energy Meter

In the Arduino IDE, go to the Board Manager and select Arduino Nano (or the board you are using). Choose the correct COM port, then click on the Upload button to flash the code onto the board.

Once the upload is complete, open the Serial Monitor from the Arduino IDE. Set the baud rate to the value used in your code (e.g., 115200).

Make sure the DC Power Monitor Module is supplied with a suitable DC source such as a battery or a variable DC power supply. Also, connect a load (for example, an LED, a DC motor, or any small DC appliance) to the selected channel.

When everything is connected, you should start seeing real-time readings of voltage, current, power, and energy appear in the Serial Monitor.

Displaying the DC Energy Meter on LCD with Arduino

So far, we have displayed the DC Energy Meter readings on the Serial Monitor. Now, let’s show the same measurements on a 16×2 I²C LCD display.

Hardware & Circuit

The LCD is powered from the Arduino’s 5V supply and communicates using the I²C interface. Simply connect the LCD’s SDA and SCL pins to the corresponding I²C pins of the Arduino (A4 for SDA and A5 for SCL on Arduino Uno/Nano).

Once connected, the real-time values of voltage, current, power, and energy can be displayed directly on the LCD screen for easy monitoring without needing a computer.

Source Code/Program

This code reads voltage, current, power, and energy values from the DC Power Monitor Module via I²C and displays them on a 16×2 LCD. It first shows a splash screen for four seconds, then alternates every three seconds between voltage/current and power/energy readings, while also printing the same data to the Serial Monitor.

Copy the following code and paste it on your main ino file. You need to add LiquidCrystal I2C to the Arduino library folder. You also need the above mentioned energy meter I2C library for reading the energy meter data.