May the EMForce Be with You

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

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 fit in the small memory and limited bit space of the Photon's ADC. It 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.

Assembly

The easy way I found to tap into an appliance without dealing with junction boxes and outlets and such: take a 3-foot appliance extension cable (15 amp rated), cut it, pass a transducer over the hot lead, re-crimp it, and you're set.

Bingo!

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

Here's the basic circuit. AC stuff is on its own board. For safety! JK. It's for noise. This circuit is completely safe.

Here's the breadboarded version with the Class C amp and LED indicator.

Close-up of the breadboard.

First 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.

I needed to remove the transducer and refit it to get the cables in the enclosure.

Oh, the hot glue! Looks horrible but it really was the best way to keep those appliance cords from wiggling around.

Perfboard installed.

Speakers on the rear plate.

Automotive store decal of BB-8... check! Officially licensed I assume.

After some careful X-Acto knifing.

Here's little BB, faithfully monitoring my electric kettle.

Glam shots...