What is it?

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

It allows a microcontroller or PLC to control high-power AC or DC loads through integrated relay outputs, making it ideal for real-world automation and control applications.

Each output is driven through opto-isolated circuitry and transistor drivers, ensuring reliable operation and proper separation between logic and field signals.

Why this board is different

Most GPIO output boards:

• Only provide low-voltage logic outputs (3.3V / 5V)
• Cannot directly drive real loads
• Require external relays or driver circuits

This module provides a complete solution:

• Integrated relay outputs (no external drivers needed)
• 24VDC system compatibility
• Optocoupler-driven control for signal integrity
• Designed for industrial environments

👉 You can directly control real devices such as relays, solenoids, lamps, and contactors without additional interface hardware

Key Features

• 16 × relay outputs (SPST normally open)
• MCP23017 I2C GPIO expander
• Optocoupler-driven relay control
• 24VDC power input
• On-board 24V → 3.3V regulator
• Output status LEDs
• Flyback protection for relay coils
• Configurable I2C address (up to 8 modules)
• Interrupt outputs (INTA / INTB)
• Reset signal access
• I2C IN / OUT connectors for daisy-chaining
• Optional onboard I2C pull-ups
• Industrial screw terminal connectors

Electrical Characteristics

• Supply voltage: 24VDC nominal
• Logic interface: I2C (3.3V)
• Number of outputs: 16
• Relay type: SPST Normally Open
• Max load current: 5A per channel
• Max load voltage:
• 30VDC
• 250VAC
• Coil voltage: 24VDC
• Coil current: ~8.3 mA per relay

Typical Applications

• PLC and embedded controller output expansion
• Industrial automation systems
• Relay and contactor control
• Solenoid and actuator driving
• Alarm and signaling systems
• Remote / distributed I/O systems

Integration

• Control outputs via I2C interface
• Daisy-chain multiple modules (up to 8 boards)
• Compatible with STM32, ESP32, and other microcontrollers

Each output can directly switch external loads without additional circuitry.

How it works

When a GPIO output is activated:

Optocoupler turns ON Driver stage energizes relay coil Relay contact closes → load is powered

When deactivated:

Relay opens → load is disconnected

This architecture provides reliable switching and isolation between control logic and field devices

Important Notes

• Designed for 24VDC industrial control systems
• Suitable for switching AC and DC loads
• Use proper wiring and load ratings
• Disconnect power before modifying connections
• Ensure loads do not exceed relay ratings