Paul Austen's CT6 Is a Raspberry Pi Pico W-Powered Four-Port Home Energy Monitor

Software engineer Paul Austen has designed a web-accessible power meter, built around a Raspberry Pi Pico W microcontroller board, which aims to provide multi-port energy monitoring for a smart home: the CT6.

"This project initially had the simple requirement [to] monitor AC power usage on several ports," Austen explains. "Given this broad requirement I initially developed a hardware device that had four ports connected to current transformers. This used an [Espressif] ESP32 microcontroller and 16-bit ADCs [Analog to Digital Converters] to measure the current flow using the current transformers. It became apparent that this approach had it's limitations which limited the accuracy of the measurements."

Facing these issues, Austen set about redesigning the project — switching from the Espressif ESP32 to a Raspberry Pi Pico W board and its dual-core RP2040 microcontroller and adding a Microchip ATM90E32AS energy metering chip to provide more accurate results — including the ability to measure each of the four ports' root-mean-square (RMS), apparent, and reactive wattage, RMS and peak current, power factor, and even the direction of power flow.

"The development of this hardware involved schematic design, PCB layout, PCB manufacture and case design of this unit. The PCB was fabricated, assembled, tested and a 3D printed case was produced," Austen explains. "This project also includes a web server that provides a useful user interface to access to the data provided by the above hardware. I also wrote an Android App that is used to connect the CT6 device to a WiFi network."

Schematics and source code for the CT6 have been released on GitHub under the permissive MIT license; Austen has also asked parties interested in buying an assembled unit or a PCB-and-case bundle to get in touch. "I have some available," he notes, "and could add them to Tindie to allow them to be purchased."