On the market, you can find many bluetooth audio kits to install on your helmet, but their prices sometimes exceed 300€. I wondered if it was possible to build one myself using parts I already owned. So I took the components of a Bluetooth speaker that no longer worked, 3d-modeled/printed a box to mount it on the helmet, made the connections with speakers from an old set of broken headphones. 

And after more than a year of use, I have no problems with it, which cost me no more than €1.50 worth of plastic filament.

I was missing a small desk lamp. I found it to be a good opportunity to learn a different type of CAD by design a base with surface functions. I then made it with my 3d printer, added an LED strip and a metal tube I already had for the neck and finally a connector hidden in the base. 

I ran into a problem with the base being to light so it would not feel solid and would slide off with a bit too much tension on the power cable. To fight this I tried different solutions like higher infill pourcentage or even adding ciment into the base.

After multiple store-bought motion detectors stopped working after a few months, I thought I'd try to solve the problem by making one myself using an Arduino board. This would also allow me to tune the sensitivity and timing to my liking.

So that's what I did, using an Arduino nano, an infrared module, a light sensor (to disable the system during the day) and my 3D printer, I made the final product which has been serving it's purpouse for serval years now.