Voice activated low cost motorized hand

Left and right are available:

Please note: I might not be able to keep the files here up to date at all times. It's better to get them from the Git repo.

I've been a maker and board member of the French e-Nable association for a few years, and I've worked on several 3D printed devices intended for people missing part of a hand or an arm.

One of the most recent of these devices is the Kinetic hand, designed by Mat Bowtell, which is easy to print and assemble, with a smoother and more natural look than older devices such as the Phoenix Unlimbited.

These devices are muscle activated and require their user to still have a functional wrist or elbow. So far I've only seen one open source low cost motor activated 3D printed device, the Exii Hackberry. It's a great device, but I found it somehow uneasy to print and assemble, it's still a bit expensive, and I thought more recent electronic components would allow going further.

Which is why in 2023 I started to work on this project to combine both new hand design, and recent electronic microcontroller to drive the servomotors. I've investigated several solutions and here is the most promising one.

You can connect your Android phone to it over bluetooth and voice control it (in english and french for now)

The cost is estimated around $60.

This is still very much a Work In Progress:

• the onboard current monitoring is still being tested and tweaked, which means for now the motors will not stop for obstacles and might hurt you (although they don't have that much strength, better safe than sorry)
• the fingers need a wire tension adjusting mount
• the pulleys might (?) become loose on the servo axle after a while
• Like the Hackberry and unlike the Kinetic, due to tight mechanical constraints, the Kinetix can't be resized to fit smaller limbs. I have another project which might help with this, that is using only one big servo for all fingers, of course with very different capabilities and features.

Github repo for the whole project including electronics, firmware and android app:

https://github.com/reivaxy/kinetix

Assembling instructions: https://github.com/reivaxy/kinetix/wiki (WIP)

If you need help please create an issue here: https://github.com/reivaxy/kinetix/issues

Since I wanted it to be servo-motor activated I needed more space inside.

The TPU articulations were wasting too much force from the servos, so I redesigned the fingers to use printed in-place joints that require no force, but will therefore not pull the finger straight when releasing the wire, which is why I set up another wire on each finger to unfold it, hence requiring more wire canals.

At some point I may also modify the cavity in the finger tops for wire tensioners contraptions, and may replace the tip by some silicon for grip.