Verified 2026-10

Grove - 4-Channel SPDT Relay

Four changeover relays behind one Grove I2C socket: an on-board controller fetches I2C commands and drives four SPDT switches, each brought out to its own 3-way screw terminal rated 10 A at 250 VAC / 30 VDC, while the module itself runs on 5 V and takes its address from 0x00-0x7F.

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Logic level5 V

Specs

MCU	MindMotion MM32F031F6P6 — Seeed states the STM32F030F4P6TR was replaced by the MM32 because of the ST shortage, and that the factory firmware differs per chip

Pinout

7 pads, as the vendor numbers them.

#	Name	Function	Signals
1	SCL	I2C clock, Grove socket	I2C SCL
2	SDA	I2C data, Grove socket	I2C SDA
3	VCC	Supply for the module: "you can use 5V for this module"	5 V supply
4	GND	Ground	ground
5	NC1	Switch 1's normally-closed throw — Seeed: "one throw, connected to COM1 by default"	relay 1 NC
6	COM1	Switch 1's common, driven between NC1 and NO1 by SIG1 — "controlled by SIG1, connected to NC1 or NO1"	relay 1 COM
7	NO1	Switch 1's normally-open throw — "the other throw of swicth1" (Seeed's own typo)	relay 1 NO

Buses

Bus	Signals	Pins	Voltage	Note
I2C ×1	SDA, SCL	SDA, SCL	5 V	the Grove socket is the module's only control path; the back of the PCB carries a second I2C header that actually works as the boot UART, which needs BOOT held high

I²C / bus addresses

Address	Bus	Device	Note
0x11 or 0x12	I2C	on-board relay controller (MM32F031F6P6)	written exactly as Seeed's spec table writes the default. Their worked example scans and reports a device found at 0x12, while the code printed on the same page writes 0x11 — which one a given unit answers at is not pinned down by the docs. Changeable over 0x00-0x7F and saved to flash (changeI2CAddress, which needs the current address to write a new one); Seeed warns the address must be set before use if you want it changed.

Power

Input	5 V on Grove pin 3 (VCC)
Input range	5 V

Seeed publishes "Nominal Coil Current 89.3 mA" and "Power Consumption abt. 0.45 W" but no board-level typical draw, so none is recorded and the two published figures are not reconciled here. Load side: TUV 10 A 250 VAC / 10 A 30 VDC, UL 10 A 125 VAC / 28 VDC, max allowable 250 VAC / 110 VDC, contact resistance 100 mOhm max, insulation resistance 100 MOhm min at 500 VDC, contact material AgCdO, 30 operations/min max, -40 to +85 C, 45-85 %RH.

Notes

Pin numbers 1-4 are the 4-pin Grove socket in the vendor's pin-map order (1 SCL, 2 SDA, 3 VCC, 4 GND — the standard Grove I2C order, and the same order as Seeed's direct-connection table of SCL yellow / SDA white / 5V red / GND black). Pins 5-7 are the three screws of Switch 1, numbered as that pin map numbers them; switches 2-4 repeat it exactly (Seeed: "the switch 1-4 have the same pin function"), but only Switch 1 is labelled in the map and the board's own top edge is silkscreened NO n / COM n / NC n per channel. The twelve screws are mains terminals, not 2.0 mm pads. The back of the PCB carries one 2x4 header doing two jobs — SDA / SCL / BOOT / GND over SWIO / SWCLK / RST(active low) / 3V3 — where SWD is what Seeed flashes firmware through, and the I2C pair on that header is really the boot UART and needs BOOT high. Design trap: I2C is the module's only control path, so the bus has to be up before any relay does anything. Unsourced here: the rail the module's own SDA/SCL pull up to — Seeed publishes the working voltage as 5 V and drives it from a 5 V Seeeduino in the example, but never states that rail, so whether a 3.3 V bus works on it is not something these pages answer. Board silkscreen reads "4-Channel SPDT Relay v1.0".

Provenance

Every figure on this page was read from the 4 sources below and last checked on Oct 16, 2026.