Mr. HandKey

Hey. This page is more than 9 years old! The content here is probably outdated, so bear that in mind. If this post is part of a series, there may be a more recent post that supersedes this one.

I could be a hand model! Right?! You can see the cuff of the dreaded sling on the bottom right. The bane of my life for 3 months.

I had an operation on my right shoulder which put my shoulder in a sling for 3 months. The sling restrained by whole arm to my torso rendering that arm moreorless unusable. It is amazing how much you use two arms for everyday task – opening jars, cutting breading dressing etc. Using a computer your effectiveness if lessened loads too. A lot of task kind of require two hands, even pretty simple operations (ctrl+c etc.) Sure you can stretch your hand to do there things but try using your computer with one hand for 5 minutes and you’ll quickly catch my drift.

Anyway, coupled up at home floating on painkillers during my recovery I decided to try and do something about it and built this device. Its real simple. You hold it in your restrained and the four buttons let you hold the modifier buttons (e.g. ctrl, alt etc) or assign full shortcuts to a button (e.g ctrl+s). One of the buttons is a function button that cycles through sets (and changes the colour of the LED so you know what you are on).

Plastic Case

The case was designed (very slowly with one hand!) in Inventor and printed on my Reprap.

Render from Inventor. No, its not red white and no, its not shiny. (And no, you have guessed it, I am not a product designer)

I printed upright like in the video because the buttons rely on the flex in the (PLA) plastic – they are monolithic to the top half of the case. Prints (particularly from my ill-tuned machine) are really anisotropic with strength when stress along the lines of the filament. Also since two halves of the case of wanted to make sure they went together snuggly so I printed at the same time so features, lips and screws flutes matches regardless of print settings.


The electronic uses an Arduino Micro (which has function to mimic a USB keyboard) a couple of buttons and resistors and the LED. Nothing complicated (complicated does not really go with opoids. Soldering one handed and does not either.

The electronics without the case. Kind of cool in a Terminator sort of way eh?


Weirdly I saw something similar on Kickstarter (after I made mine ;)) called the Trickey. Like the name – so much that I ripped it off for naming mine! Well, you have to have a name right! Not sure how Trickey did, can’t imagine it’ll make it’s designed millions. Kind of think mine better to be honest (though mine does look like something out of the soviet era…but I kind of like that look!). I would find all the separate keys for the Trickey kind of annoying and unnecessary.

I do think though (and I know this is hardly an original idea – just google ‘printed arms for disabled’) there is real scope for stuff like this to help people with disabilities/ the elderly. And I am not sure they need to be hi-tech lo-fi stuff like robotics hands.