Design and Performance Evaluation of an ESP-NOW Based Dual-Channel Smart Plug for Real-Time Energy Monitoring and Comparative Load Analysis

Abstract

The paper proposes a smart plug system with dual channel to monitor energy consumption and to conduct comparative analysis of loads in real-time, which is implemented on an ESP8266 microcontroller unit for wireless data communication. The proposed system has two energy measuring modules (PZEM-004T) to measure voltage, current, power, energy consumption, frequency and power factor of two independent electrical loads. The ESP8266 NodeMCU is used to process the data and send it wirelessly to a dedicated receiving unit using ESP-NOW. The measured parameters and system status are displayed on a 16×2 LCD in the receiver unit. A SoftAP (Software Access Point) is used to gain local wireless access for monitoring and control. This is to create a smart plug, which is low cost and reliable enough to work in places where there is no internet connection or non-continuous internet connection; for this reason, this smart plug does not need to have any internet connection, router or cloud server. The system enables comparative analysis of the electrical parameters of two connected loads and near-real-time evaluation of their power and energy consumption. Measurement accuracy was evaluated using five representative loads, including resistive, electronic, SMPS, and universal-motor loads, by comparing the proposed system with a commercial energy meter. The results yielded a mean absolute power error of 2.74% and a mean power-factor error of 1.75%. The DC-side self-consumption of the transmitter board was also evaluated under different relay operating states, with measured power consumption ranging from 0.454 W in the idle state with both relays OFF to 0.873 W with both relays ON. Relay-based load control, timer automation, threshold-based load disconnection are combined to enhance reliability and safety. The Packet Delivery Ratio (PDR) is used to measure the communication performance of the ESP-NOW link at various distances. The experimental data indicates that PDR remains above 97% up to 10 m away, indoors, and demonstrates good wireless communication for real-time monitoring. It has been reported in the literature that ESP-NOW can decrease power consumption and the latency of communication compared to traditional Wi-Fi-based methods, since it does not rely on continuous network association and the overhead of TCP/IP. The implemented prototype offers a compact and low-cost embedded system solution for smart homes, educational laboratories and small-scale industrial energy management systems. The Embedded Systems and Energy Monitoring ESP8266 programmer is a compact, USB-powered microcontroller development board that supports the ESP8266 Wi-Fi module. The Energy Monitoring programmer for Embedded Systems is a small, USB powered microcontroller development board based on ESP8266 Wi-Fi module.