Cascadable and Intelligent Power Switches for Manufacturing and Home-Automation

By Nulltek

There are multiple situations where automated switching of low-voltage power supplies to equipment is required. Such as cycling power to UUTs in production test, or programatically enabling power to home automation systems to name a few.

There are several limitations of existing systems. These systems are often tailored to a set number of outputs, which is awkward since everyone has different application requirements. Alternatively they can be unrealistically expensive, or have insufficient features for many niche applications. This was the origin of the NullTek Cascadable and Intelligent Power Switches (CIPS), an open-source project which aims to solve the above issues.

Key Goals for this Project:

  • Cascadable such that the number of outputs can be infinitely scaled.
  • No configuration required, each switch is address by its location in the serial chain. Ability for blind system mapping.
  • Implements half-duplex 1-wire error-resistant NPC serial protocol.
  • Feedback provided from each switch, voltage and current measurements can be obtained.
  • Support for 5-30V switching. Support for lower voltages through LDO isolation.
  • ~$10 BOM cost per switch.

This project let me exercise my electronics chops, while learning a few new CAD tools. I am a huge advocate for open-source, and so to reduce my own hypocrisy of primarily using Altium and Solidworks, this project is entirely developed using opensource tools. Because I am starting from almost scratch with these tools, I decided to build every part of the project from scratch and not cheat using built in libraries, this means all the Symbols, Footprints, 3D Models are custom developed for this project. The result of this decision was a much steeper but more rewarding learning curve for KiCad & FreeCad.

The prototype layout of the switch.

Now that the design and CAD are out of the way it’s just a case of organizing the parts, and writing the software. With the encouragement of 4RF management and because this project was completed outside of company hours, it will be released as open source under the GPL license, allowing unrestricted use for all.