Dr. Wattson

Energy Monitoring Breakout Board for Arduino, Raspberry Pi and other Maker-Friendly Microcontrollers. Easily integrate quality AC energy measurements into your next project!

What is it?

Dr. Wattson is a new energy monitoring breakout board from Upbeat Labs.

Based on the MCP39F521, a single-phase power monitoring chip from Microchip, it is coupled with a rich Arduino library to facilitate energy monitoring without much ado. The board is designed to be tolerant of a wide range of voltages, which means that it can also be used with the Raspberry Pi or any other 3.3v MCUs just as easily.

As of September 6th, 2018, a Python library for Dr. Wattson, for use with Raspberry Pi (or BeagleBone Black) is now available! :-)

Dr. Wattson makes Professional-Quality energy monitoring and measurement available to the Maker, catering to both the novice and advanced user! The unit comes pre-calibrated (enabling measurements from 1mA up to 4A) to enable you to start taking quality measurements on the get-go with just a couple of simple commands.

If you are a more advanced user, you have a wide range of functionality available from the rich library, as well as the ability to tweak the hardware to suit your needs and recalibrate using the library.

Measure Big. Or Small

Whether you want to measure small standby power consumption or larger loads, Dr. Wattson has you covered. Boasting a 4000:1 Dynamic Range, and capable of 0.1% accuracy, the MCP39F521 is a versatile chip, allowing you great flexibility with measurements. Dr. Wattson takes that flexibility and makes it easy to use! Dr. Wattson comes calibrated to measure currents from 1mA up to 4A.

Arduino Library

A comprehensive, yet easy-to-use Arduino library means you can integrate this into your application and jump right away into making measurements and other functionality.

Python Library

A comprehensive, yet easy-to-use Python library using smbus2 means you can now easily use Dr. Wattson with Raspberry Pi (or BeagleBone Black) and integrate it into your next project.

Quality Construction

Environmentally friendly and high-quality ENIG finish with 2 oz copper and wide high-voltage-traces and quality components lets you use it to measure power in systems up to 12A or more!

(traces 10A @ 10˚C rise, 15A @ 25˚C rise, with the terminal connectors rated for 300V, 12A)

Since it is an isolated design, you can bypass the board completely for high current, bypassing the high current neutral line through the CT core and bypassing the board altogether. (You will still need to connect AC line and neutral IN for enabling voltage measurements via the voltage transformer)

It includes 4 mounting holes (2-56) to enable you to put it into a safe enclosure.

Use up to 4 boards with a single MCU

Solder jumpers on the board enable you to pick from 4 possible I2C addressing schemes, allowing you to control 4 of these boards from a single MCU using the same I2C bus.

ZCD and Event pins

Use the Zero Cross Detector (ZCD) output to orchestrate any synchronization like firing a Triac for dimming, or making a clock based on your AC line frequency!

The event pin gives you output indication on the presence of configured events of interest, like voltage surge/sag, over-current, over-power.

Configure the events of interest via the Arduino/Python library, and get notifications by connecting these pins to any externally interruptible pin in your MCU. Using the library, you can then query the board to find out which event occurred.

MCU friendly

While the board is powered by 3.3v, it includes a Vin pin (set it to your MCU voltage) and bi-directional level shifting on all IO pins, so you can use a 5v system or a 3.3v system without any modifications or need for level shifting.

What you will need

You are purchasing the Dr. Wattson Energy Monitoring Board. In addition, you will need the following:

• enclosure to put the Dr. Wattson Energy Monitoring Board in, so the rest of your project is shielded from high voltage connections. We have an enclosure kit for sale, or you can make your own.
• Micro-controller. Dr. Wattson comes with an Arduino library and Python library for Raspberry Pi and BeagleBone Black.

Why did you make it?

I worked on a Smart Outlet project called BuffI the Ampere Slayer (see my presentation from Maker Faire 2017 in San Mateo, CA - https://youtu.be/LzQakUzzlg4), and part of the work that was done there was to enable quality energy monitoring, including the ability to measure small standby power consumption. I thought that a well-calibrated breakout board to make quality energy monitoring as a subcomponent available to the Maker community would be very useful, and so I decided to create Dr. Wattson and put in all the features that I wanted to see, as a Maker myself.

What makes it special?

• Calibrated to get quality measurements right off the bat
• Isolated design
• Works with 5v and 3.3v MCUs without any modifications
• Connect up to 4 energy monitors with I2C addressing configuration
• Arduino library for easy use
• Raspberry Pi library under development (Update: September 6th, 2018 - Python RPi library now available!)
• Available enclosure kit

Other resources

• How to build an Arduino Energy Logger & plot the data

• Easy Energy Monitoring with Arduino and Dr. Wattson - presentation at MakerFaire Bay Area 2018

• Internet-connected Energy Monitoring with Raspberry Pi, Dr. Wattson & AWS