TRIAC BLOC – a solid-state relay with I2C interface

From time to time I get requests to make some high power switching, so I decided to design a solid-state relay that could handle a lot of different situations. The most common use for it I have is refurbishing old ceramic kilns. Since our technical life is close to the stage (both theatre and music), I also wanted it to be usable as a dimmer module. And, just for kicks, as a single phase AC motor speed controller, in case we would want that.

So here it goes. The design and code are on github: I still have some spare boards and parts if anyone is interested – drop me a note (mic at


  • maximum power – 6kW
  • zero crossing detection
  • controllable via I2C protocol
  • linear output power control
  • phase shift dimmer mode
  • switch at zero-crossing mode
  • output filtering for dimmer mode
  • snubber network
  • “low level” zero-crossing signal output
  • triac trigger signal input
  • 4 spare MCU pins available for additional features
  • open source hardware and firmware

TRIAC BLOC - a solid-state relay with I2C interface

Since deep in my heart I’m still a programmer, I wanted digital control that would solve some issues, like being able to set the output power in a linear manner. But nevertheless, the module is still usable without a microcontroller – zero-crossing and turn on signals are available on a separate header on the board. You can add or remove components based on particular needs. No need for dimming or motor control? Skip the filter choke and snubber. Want to integrate it into existing digital solution? Skip the micro and use zc and trigger signals directly.


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About The Author

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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