Brian Chamberlain
Software Engineer & Electronics Nerd

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Power sensing BB-8

A fun way to monitor appliances in your house. I designed this project as part of a Star Wars contest for BB-8 will make noises at you when the water has finished boiling.

This project is also on

May the EMForce be with you

I designed this project as part of a Star Wars contest for You can see the full details of this project on

This was a really fun project. I especially enjoyed trying to figure out how to use the built in ADC on the Photon to drive a Class C amp and a pair of small speakers. There's a little python script I wrote to take any WAV file and unpack it to get it to fit in the small memory and limited bit space of the Photon's ADC. I basically converts it to a very large header file. See one sample file here Super hacky, but it was a contest on a deadline. Here's the python script that does the conversion

I hope I can hack on something like this again soon.

The easy way I found to tap into an appliance w/o dealing with junction boxes and outlets and such. Take a 3ft appliance extension cable (15 Amp rated) and cut it, pass a transducer over the hot lead, re-crimp it and you are set. bb8 appliance cable Bingo! bb8 transducer inline

Here you can see the 60Hz AC line running between 1.0-2.0V approx. The circuit I built shifts the AC power signal to that range so it can be sampled with DAC on the Photon. The circuit was tuned to get the right range to maximize sampling resolution. bb8 powerline scope

Here is the basic circuit... AC stuffs on it's own board. For safety! JK. It's for noise. This circuit is completely safe. bb8 ac circuit

Here is the breadboarded version with the Class C Amp, LED indicator. bb8 breadboard test Close up of the breadboard bb8 breadboarded

First test! bb8 appliance test

Sure I could have done a cool 3D printed case. I wanted to... but this was for a contest and I was running out of time and budget. bb8 enclosure masking

Needed to remove the transducer and re-fit it to get the cables in the enclosure. bb8 power assembly

bb8 glued power line Oh the hot glue! Looks horrible but it really was the best way to keep those appliance cords from wiggling around and such. bb8 perfboard installed Speakers on the rear plate. bb8 speaker mount Automotive store decal of BB-8... check! Officially licensed I assume. bb8 decal After some careful x-acto knifing bb8 decal enclosure Here is little BB, faithfully monitoring my electric kettle. bb8 kettle monitoring Glam shots... bb8 completed front bb8 completed back

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