I made a wrist-worn shake-activated stungun
StunlyAfter my sister had a scary encounter in the park, I set out to make a stungun that could be operated hands-free, so there was no excuse to leave it at home.
An onboard accelerometer detects an intentional double-shake of your wrist to set it off. I designed the circuit and PCB, drew the enclosure in CAD, and wrote the firmware.
The final product worked, but I kinda burned out doing all this by myself and still had yet to run a Kickstarter campaign and make custom injection molds for manufacture.
Teeny tiny parts
The biggest challenge of this project was making the darn thing small enough
Baking an early prototype
I didn't have a reflow oven, so I made one with a toaster oven and a kit
Measuring and plotting accelerometer response
Plotting the accelerometer readings in Python to dial in the best settings
The profile of a double-shake
We want it to trigger during an intentional shake, but not from normal running
Running in the lab like an idiot
Strapping a wired-in early prototype to my arm and jogging in place to get live readings
Soooo maaany batteries..
Tested batteries on the bench across dozens of manufacturers (pro tip: manufacturers lie)
An enclosure rendering
Things always look so much bigger on your screen than when 3D printed
You want renderings? I've got plenty