I made a wrist-worn shake-activated stungun


After 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.

A PCB with small components

Teeny tiny parts

The biggest challenge of this project was making the darn thing small enough

A PCB being baked in a reflow toaster oven

Baking an early prototype

I didn't have a reflow oven, so I made one with a toaster oven and a kit

Sensor readings graphed on a computer screen

Measuring and plotting accelerometer response

Plotting the accelerometer readings in Python to dial in the best settings

Equations on a whiteboard

The profile of a double-shake

We want it to trigger during an intentional shake, but not from normal running

A man who is doing embarrassing things in the name of technological progress

Running in the lab like an idiot

Strapping a wired-in early prototype to my arm and jogging in place to get live readings

Dozens of small lithium polymer batteries on a workbench

Soooo maaany batteries..

Tested batteries on the bench across dozens of manufacturers (pro tip: manufacturers lie)

A CAD rendering of a custom electronics enclosure

An enclosure rendering

Things always look so much bigger on your screen than when 3D printed

A 3D rendering of a wrist-worn stungun

You want renderings? I've got plenty

But who cares, no big deal, I want morrrre!

© Copyright 2019– Joel Wigton, All Rights Reserved.