UART RS485 interface board

ESP32 PV Power Monitoring System

This project documents a system for monitoring photovoltaic (PV) power production and household power consumption using ESP32 and PZEM-004T / PZEM-016 power sensors, with data published over MQTT.

Included in this repo:

• Firmware for several ESP32 individually configured breakout boards, built with ESP-IDF 5.3
• Python utility for configuring PZEM modules over USB serial
• Hardware project for a custom UART ↔ RS485 interface board (KiCad) for a simple stripboard

Dashboard Demo

The following screenshots show the resulting dashboard created using Node-RED where the sensor data is received via MQTT and stored in a database. The charts visualize all sensor values across multiple inverters and locations.

Live Chart View (Total sum, Active power, Current)

Live Chart View (Power factor, Voltage, Frequency)

Hardware Setup

Below are a few example photos of the current wiring and hardware setup.

3x PZEM-003T measuring total consumption (main distribution board)

Used for measuring total consumption of the entire building. One module for each phase (L1, L2, L3).

Single PZEM-004T (inverter distribution box)

Each module is wired to one phase of a single inverter output.

2× PZEM-016 via RS485 (distribution box Remote inverters)

PZEM-016 modules connected via a shared RS485 bus and assigned separate Modbus addresses.
On the other side of a ~30 m 5×1.5 mm² power cable, an ESP32 with a custom RS485-to-UART PCB receives the data and publishes it via MQTT.

UART ↔ RS485 Interface (Custom PCB)

To interface the ESP32 with RS485-based PZEM-016 sensors, a small PCB based on the MAX3485 transceiver was created.

• KiCad Project: hardware/UART-RS485_interface-board/
• Schematic PDF: schematic.pdf

Photo while testing

Firmware (ESP32)

Firmware for reading multiple PZEM modules and publishing the values via MQTT.
Tested with ESP-IDF 5.3.

Features

• Supports PZEM-004T v3 (TTL UART) and PZEM-016 (RS485)
• Configurable (per module):
  • Sensor address
  • GPIO pins (TX, RX, RTS)
  • MQTT topic prefix
  • Publish interval
  • Sensor type (TTL / RS485)
• Reads and publishes:
  • Voltage
  • Current
  • Power
  • Energy
  • Frequency
  • Power factor

Build and Flash

Make sure ESP-IDF 5.3 is sourced:

. /opt/esp-idf-v5.3/v5.3/esp-idf/export.sh
cd esp32_power-monitor
idf.py build flash monitor

Python Utility (power-meter.py)

Utility script for directly configuring and reading PZEM modules using a USB-to-Serial adapter.

Functions

• Set or change Modbus address
• Reset energy counter
• Read live values

Requirements

pip install pyserial

Usage

1. Connect RX/TX of the FTDI adapter to the TX/RX of the PZEM module.
2. Plug the adapter into your PC.
3. Edit pzem_tool.py:
   • Set the correct serial port and slave ID
   • Uncomment the function you want to run (read, configure, reset)

Then run the script:

python3 pzem_tool.py

Repository Structure

firmware/    # Several ESP-IDF projects for all instances running
hardware/UART-RS485_interface-board/   # KiCad project for interface PCB
doc/images/                            # photos and documentation

Notes

• PZEM modules must be addressed and wired correctly (especially for RS485).
• Each PZEM sensor input should be fused and installed safely. Here i used a 200 mA 5x20 mm fuse for each module in the gray WAGO fuse holders for DIN rail.
• Wi-Fi credentials are configured via main/credentials.h which is not tracked in the repo.