Description Unit 4Relay is a Grove-connected 4-channel relay unit controlled over I2C. Built around the STM32F030F4P6 microcontroller, the Unit 4Relay independently controls four mechanical relays for AC 250V or DC 28V switching, with 10A rated current and 16A maximum instantaneous current. Each channel on the Unit 4Relay has its own programmable status indicator, and the relay side is physically isolated from the low-voltage control side. With I2C address 0x26, compact 112.0 x 23.0mm form factor, and LEGO-compatible mounting holes, the Unit 4Relay is practical for smart home, industrial control, and digital power switching projects. Features Unit 4Relay provides four independently controlled relay channels. Supports AC 250V@10A or DC 28V@10A load switching. Each Unit 4Relay channel has a programmable LED status indicator. I2C communication over the HY2.0-4P Grove interface at address 0x26. Physical isolation between the high-voltage relay side and low-voltage control side. Two LEGO-compatible mounting holes for structured installation. Compatible with UiFlow1, UiFlow2, Arduino IDE, and Home Assistant workflows. Specifications Specification Parameter MCU STM32F030F4P6 Max Input Voltage AC 250V / DC 28V Rated Current 10A Max Instantaneous Current 16A Communication Interface I2C @0x26 Product Size 112.0 x 23.0 x 18.0mm Product Weight 40.0g Package Size 163.0 x 100.0 x 20.0mm Gross Weight 84.0g Applications DC signal switching with Unit 4Relay. Power on/off control for digital devices. Smart home relay switching. Industrial control and power management for high-power equipment. Product List 1 x Unit 4Relay 1 x HY2.0-4P Grove connection cable (20cm) 4 x VH3.96-4P terminals Other Content PinMap HY2.0-4P Black Red Yellow White PORT.A GND 5V SDA SCL I2C Control The Unit 4Relay uses I2C protocol at address 0x26. The mode control register supports manual LED control or automatic LED sync with relay status, while the relay control register switches LED1-LED4 and RELAY1-RELAY4. Development The Unit 4Relay can be developed with UiFlow1, UiFlow2, Arduino IDE, and Home Assistant. These options make Unit 4Relay integration straightforward for controller projects that need four separated relay outputs. Resources 4-Relay Unit product document 4-Relay Unit schematics PDF 4-Relay Unit model size image 4-Relay Unit structure files 4-Relay Unit M5Core Arduino example 4-Relay Unit UiFlow2 API documentation 4-Relay Unit Home Assistant integration 4-Relay Unit PDF document FAQ How many relay channels does Unit 4Relay provide? The Unit 4Relay provides four independently controlled relay channels. What load voltage and current does Unit 4Relay support? The Unit 4Relay supports AC 250V@10A or DC 28V@10A load switching, with 16A maximum instantaneous current. What communication interface does Unit 4Relay use? The Unit 4Relay uses I2C over the HY2.0-4P Grove interface, with I2C address 0x26. Can Unit 4Relay indicators be programmed? Yes. Each Unit 4Relay channel has a programmable LED status indicator, and the LEDs can work in manual mode or sync automatically with relay status. What is included with Unit 4Relay? The package includes 1 x Unit 4Relay, 1 x HY2.0-4P Grove connection cable (20cm), and 4 x VH3.96-4P terminals.
