Industrial I/O Controller (24 V)
24 V industrial controller: four isolated inputs, four relays, Ethernet and USB.
The brief
The same networked controller as the 5 V version, but running from a 24 V industrial supply. That changes the front end completely: the supply chain has to survive 24 V, and the field inputs have to work at 24 V logic levels rather than 5 V ones.
Reverse-polarity protection, a fused input and a two-stage conversion down to the logic rail are what make it safe to hand to a panel installer.
What we did
A networked industrial-style controller built around the ESP32-S3-WROOM-1. It reads four isolated inputs, switches four relay outputs and connects over Ethernet or USB. It runs from a 24 V supply.
- Main controller: The ESP32-S3-WROOM-1 module handles logic and connectivity, with a status RGB LED.
- Wired Ethernet: A W5500 controller with an RJ45 magjack and a 25 MHz crystal connects to the ESP32 over SPI, giving stable network communication.
- Isolated inputs: Four optocoupler-isolated inputs (PC817) with input filtering protect the microcontroller from field wiring.
- Relay outputs: Four 24 V relays (G5Q-14) are each driven by a transistor stage with a flyback diode and indicator LED. Each relay has a screw-terminal output with COM, NO and NC contacts.
- Power supply: A fused 24 V input has reverse-polarity protection (LM74610 smart diode controller with a MOSFET). An LM2596S-5 buck converter produces 5 V, and a TPS62133 buck converter produces 3.3 V for the logic.
- USB and programming: USB-C (OTG) with auto boot and reset transistors, plus manual BOOT and RESET buttons for firmware upload.
Design details
Design summary
| CAD tool | KiCad |
|---|---|
| Overview | A networked industrial-style controller built around the ESP32-S3-WROOM-1. |
| Main controller | The ESP32-S3-WROOM-1 module handles logic and connectivity, with a status RGB LED. |
| Wired Ethernet | A W5500 controller with an RJ45 magjack and a 25 MHz crystal connects to the ESP32 over SPI,… |
| Isolated inputs | Four optocoupler-isolated inputs (PC817) with input filtering protect the microcontroller from… |
| Relay outputs | Four 24 V relays (G5Q-14) are each driven by a transistor stage with a flyback diode and… |
| Power supply | A fused 24 V input has reverse-polarity protection (LM74610 smart diode controller with a… |
| USB and programming | USB-C (OTG) with auto boot and reset transistors, plus manual BOOT and RESET buttons for… |
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