SparkFun Qwiic Single Relay

Have you ever wanted to control something powerful or have you ever needed to turn on/off a high power device from your Arduino or another low powered microcontroller? The SparkFun Qwiic Single Relay provides you with the easiest to use relay yet. The Single Relay board can handle up to 5.5A at 240VAC for long periods of time and allows you to control large power loads with simple I2C commands. Utilizing our handy Qwiic system, and on-board screw terminals, no soldering is required to connect it to the rest of your system!

The Qwiic Relay comes with a default I2C address of 0x18 but can be changed with a simple command allowing you to control over 100 Qwiic Relays on a single bus (but please be aware that toggling lots of relays on a 3.3V bus can cause voltage spikes so an external power supply will be required)! In addition, there is an address jumper on the back of the board. Closing this jumper with solder will change the address to 0x19.

We've included many safety precautions onto the PCB including, ground isolation between the load and the low voltage control has been increased and an air-gap has been added around the common pin. The traces between the relay and the NC/NO/COM terminals have been doubled to increase the maximum current. But if you aren't comfortable playing with high voltage AC, that's understandable. Please consider using the IoT Power Relay, instead. It's not I2C supported but the IoT Power Relay contains shielding to prevent accidental shock and is great for learning how to use relay power accessories.


The SparkFun Qwiic Connect System is an ecosystem of I2C sensors, actuators, shields and cables that make prototyping faster and less prone to error. All Qwiic-enabled boards use a common 1mm pitch, 4-pin JST connector. This reduces the amount of required PCB space, and polarized connections mean you can’t hook it up wrong.


  • Operating Voltage: 1.7V-3.6V
  • Coil Resistance: 23.5Ω
  • I2C Address: 0x18 (Default), (Jumper changes to 0x19)
  • Max Current (Through Relay): 5.5A (240 VAC)

SparkFun Qwiic Single Relay Product Help and Resources

Qwiic Single Relay Hookup Guide

January 3, 2019

Get started switching those higher power loads around with the Qwiic Single Relay.

Core Skill: DIY

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1 DIY

Skill Level: Noob - Basic assembly is required. You may need to provide your own basic tools like a screwdriver, hammer or scissors. Power tools or custom parts are not required. Instructions will be included and easy to follow. Sewing may be required, but only with included patterns.
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Core Skill: Programming

If a board needs code or communicates somehow, you're going to need to know how to program or interface with it. The programming skill is all about communication and code.

2 Programming

Skill Level: Rookie - You will need a better fundamental understand of what code is, and how it works. You will be using beginner-level software and development tools like Arduino. You will be dealing directly with code, but numerous examples and libraries are available. Sensors or shields will communicate with serial or TTL.
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Core Skill: Electrical Prototyping

If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.

3 Electrical Prototyping

Skill Level: Competent - You will be required to reference a datasheet or schematic to know how to use a component. Your knowledge of a datasheet will only require basic features like power requirements, pinouts, or communications type. Also, you may need a power supply that?s greater than 12V or more than 1A worth of current.
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