I spend hours sitting in front of my computer. What if I could ride my computer instead? After noticing a few pedal-powered sockets in train stations in France, and a few videos of DIY versions of the same idea, I wanted to try making one by myself.
I took an old bike and built a stand for it. The stand is simple and non-intrusive so that I can unmount it easily and restore the original functionality of the bike.
I asked for a car alternator in a garage and they gave me one they were disposing of. One connection was broken but after some soldering it works like a charm. One interesting thing about this kind of alternator is that spinning it as such does not generate any current, because there is no permanent magnet inside. The magnetic field is generated by a self, so You need to bootstrap the process by applying 12V to the self first, start spinning the alternator, and then it will maintain the magnetic field by itself, with the current it produces.
I hooked the alternator to the bike using a lawnmower belt. I suspect that this part is quite inefficient. Other pedal-powered systems I have seen online tend to use friction directly on the wheel instead.
The alternator produces 12V DC and my laptop charger expects 230V AC. Fortunately this is a fairly standard conversion and I bought a converter that does that (this is essentially the only piece of equipment I had to buy for the whole system).
And that's basically it, really. The boot process is quite simple: get on the bike, spin the pedals, turn on the 12V tension to bootsrap the alternator, the AC/DC converter lights up, turn off the 12V tension, and then… boot the laptop!
And… it works! Kind of. Because the system is very inefficient so I have to pedal quite hard to power my small Thinkpad X201. The commercial systems I have tried are much more efficient (I don't make any effort to power the ~20W of my laptop with them). So, to actually work with this setup, I would need to buy a properly manufactured system like this. Unfortunately I have not found anything that matches my needs: it must provide a power socket (220V); it must be a single system for personal use (I am not a company); * ideally it should be adaptable to an existing desk.
If you can find anything like this please do get in touch, as I still have this dream in the back on my mind...