SparkFun Qwiic Dual Solid State Relay

The SparkFun Qwiic Dual Solid State Relay is a power delivery board that allows users to switch two AC loads from a low-power microcontroller using the SparkFun Qwiic Connect System. The board features two 25A/250VAC solid-state relays that utilise the Zero Cross Trigger method, so you can toggle two loads on a 60Hz AC carrier signal on and off up to 120 times per second!

Scalable I²C Control

An ATTiny84 acts as the "brain" of the SparkFun Qwiic Dual Solid Relay, accepting I²C commands to toggle the two relays, as well as a few other special commands. By default, the board uses the I²C address 0x0A, but an alternate address (0x0B) is easily accessible via a jumper selection. Because the I²C address of the ATtiny84A is software configurable, or if you have a seriously big power project in mind, you could daisy chain over 100 Qwiic Dual Solid State Relays on a single bus without running out of control lines!

Built-In Safety Upgrades

Needless to say, switching high-voltage AC loads requires serious precautions, so we integrated specific hardware features to keep your low-voltage circuitry safe during operation:

• Ground Isolation: Complete physical separation between the high-voltage relay side and your sensitive control circuitry.
• Milled PCB Clearances: Air-gaps milled directly into the board isolate each side of the AC line to prevent electrical arcing.
• Zero Cross Trigger: Ensures the AC load is only switched when the voltage crosses zero, minimising electrical noise and wear on the relay components.

Even with these built-in safety features, this board is designed strictly for users who are experienced and knowledgeable about handling high AC voltage safely. If you are not completely comfortable working with exposed mains power, we strongly recommend checking out the fully enclosed IoT Power Relay as a safer alternative for your power projects. While it's not I²C supported, it contains complete shielding to prevent accidental shock and serves as an excellent starting point for learning about relay power accessories before moving up to this bare-board solution.

• Schematic
• Eagle Files
• Hookup Guide
• Datasheet (SSRF-240D25 Relay)
• Board Dimensions
• Qwiic Resource Page
• Libraries:
  • Arduino
  • Python / MicroPython / CircuitPython
• GitHub Hardware Repo