What is it?

This is an 8-channel industrial relay output module designed for 24VDC control systems, based on the MCP23008 I2C GPIO expander.

It enables a microcontroller or PLC to control real-world loads (AC or DC) through integrated relay outputs, making it ideal for automation, control panels, and embedded systems.

Each output is driven through opto-isolated circuitry and transistor drivers, ensuring reliable switching and improved signal integrity.

Why this board is different

Most GPIO output boards:

• Only provide low-voltage 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 hardware required)
• 24VDC industrial system compatibility
• Optocoupler-driven control for improved reliability
• Designed for real control applications, not just prototyping

👉 You can directly switch relays, solenoids, lamps, and other loads without additional interface circuits

Key Features

• 8 × relay outputs (SPST normally open)
• MCP23008 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 output (INT)
• 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: 8
• 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 ensures reliable switching and separation between 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