What is it?

This is a 16-channel industrial digital input module designed for 24VDC systems, based on the MCP23017 I2C GPIO expander.

Unlike typical low-voltage GPIO boards, this module is built for real-world applications, allowing you to directly interface with 24V sensors, switches, and control signals.

Each input is opto-isolated and conditioned, providing reliable and noise-resistant signal acquisition for embedded systems and industrial control panels.

Why this board is different

Most I2C GPIO expanders:

• Operate at 3.3V / 5V only
• Require external signal conditioning
• Are not suitable for industrial environments

This board solves that by providing:

• Direct 24VDC input compatibility (PNP / sourcing signals)
• Opto-isolation between field and logic
• Integrated protection (TVS, reverse polarity)
• Per-channel filtering for noise reduction

This allows direct connection to real industrial signals without additional interface circuits.

Key Features

• 16 × 24VDC digital inputs (PNP / sourcing)
• Opto-isolated inputs (field side isolated from logic side)
• MCP23017 I2C interface (3.3V logic)
• On-board 24V → 3.3V regulator
• Per-channel input protection and filtering
• TVS surge suppression + reverse polarity protection
• Interrupt outputs (INTA / INTB)
• Reset signal access
• Configurable I2C address (up to 8 modules)
• I2C IN / OUT connectors for daisy-chaining
• Optional onboard I2C pull-ups

Electrical Characteristics

• Input voltage: 24VDC nominal
• Input type: PNP (sourcing)
• Detection levels:
• ON ≥ 12V (recommended)
• OFF ≤ 5V
• Input current: ~6.8 mA per channel @ 24V
• Logic interface: I2C (3.3V)

Typical Applications

• PLC and embedded controller input expansion
• 24V sensor interfacing (proximity sensors, limit switches, etc.)
• Industrial control panels
• Alarm and status monitoring systems
• Remote / distributed I/O systems

Integration

• Connect 24V signals directly to input terminals
• Communicate via I2C
• Daisy-chain multiple modules (up to 8 boards)

Designed to work seamlessly with STM32, ESP32, and other microcontrollers.

Important Notes

• Designed for 24VDC industrial systems only
• Inputs are PNP (sourcing type)
• Field side is opto-isolated from logic side
• Do not exceed intended input voltage levels
• Power down before wiring changes