Wiznet makers

A Hardware-Focused Look at an Ethernet-Controlled Industrial I/O Board

Wired Ethernet remains a reliable and interference-resistant communication method for industrial control systems.
This article examines a publicly shared hardware project that integrates the ESP32-S3 microcontroller and the WIZnet W5500 Ethernet controller to build a 20-channel actuator controller.

Although the repository does not include software, the complete schematic provides a clear view of how a network-controlled industrial output board can be designed.

1. Overview

The board integrates four major functional blocks into a single PCB:

1. ESP32-S3 – main controller
2. WIZnet W5500 – wired Ethernet interface
3. 24-V power input stage – industrial-grade power handling
4. 20 MOSFET-based SSR outputs – for controlling external loads

Together, these blocks form a network-enabled multi-channel actuator/relay controller suitable for automation and distributed I/O applications.

2. Power Stage – Designed for Industrial 24-V Systems

The schematic (Page 1) shows that the board is powered by a 24-V DC input, a common standard in factory automation.

The power circuitry includes:

• Reverse-polarity protection
• TVS diode protection
• High-current fuse
• 24 V → 5 V buck converter (LMR51430)
• 5 V → 3.3 V LDO regulator (LD39200)

This topology ensures stable operation of the ESP32-S3 and W5500 in demanding environments.

3. Main MCU – ESP32-S3

The board uses the ESP32-S3-MINI-1 module as the primary processor and communication controller.

Key components include:

• USB-C connector for programming
• ESD protection
• Boot and reset circuitry
• Access to SPI/GPIO pins

The ESP32 manages network commands, executes control logic, and drives the output channels.

4. Networking – WIZnet W5500 Ethernet Controller

One of the most notable aspects of this design is the use of the W5500 hardwired TCP/IP controller to implement wired networking.

The Ethernet section (Page 3) includes:

• W5500 chip
• 25-MHz crystal
• SPI connection to ESP32-S3
• LINK/ACT indicator LEDs
• ESD protection
• RJ45 connector with integrated transformer

By using the W5500, the board offloads network traffic processing and ensures deterministic Ethernet behavior—important for industrial and automation environments.

5. Signal Buffering – 20-Channel Level Isolation

Between the ESP32 and the SSR outputs, the design includes five SN74LV4T125 buffer ICs.

These devices:

• Protect ESP32 GPIO pins
• Provide stable logic levels
• Improve noise resistance
• Deliver 20 independent buffered output signals

This stage is essential for reliable multi-channel actuation.

6. Output Stage – 20 MOSFET SSR Channels

The output stage (Page 5) consists of:

• 20 OMRON G3VM-61BR2 MOSFET solid-state relays
• Individual series resistors for each SSR input
• 20 output terminals for external loads

The SSR-based design is suitable for driving common 24-V loads such as:

• Solenoid valves
• Relays
• Pneumatic or hydraulic actuators
• Small DC loads

Each channel provides clean ON/OFF switching without mechanical relay wear.

7. Output Protection and Indicators

Each output channel includes:

• A flyback diode for inductive load protection
• An LED indicator showing channel state

These are standard features in industrial I/O modules for diagnostics and safe operation.

8. What This Board Represents

From the schematic alone, the purpose of the hardware is clear.
The combination of:

• 24-V supply
• 20 SSR channels
• Wired Ethernet
• Dedicated buffers
• Protection circuits

indicates that this is a remote I/O module designed to control 24-V actuators through a network.

Typical use cases include:

• Automation equipment
• Distributed industrial I/O
• Solenoid and valve control systems
• Network-controlled relay banks
• Machinery integration via TCP/UDP

This is effectively an Ethernet-controlled 24-V output controller.

This project showcases a fully integrated ESP32-S3 + W5500 20-channel actuator controller, capable of driving 24-V loads over a wired Ethernet connection.
The schematic highlights industrial-grade power handling, reliable network communication, buffered logic control, and MOSFET-based outputs—making the design a strong reference for embedded and automation engineers.