Most stationary bikes have a flywheel. You could 3D print a gearing set to run a small generator (like this one or DC) off if it. There are tutorials out there about how to set up it up.
I actually did that with an actual bicycle and one of those “make any old bike a stationary bike” stand things. Harvested an old motor out of…what was it, a printer or something? Photocopier? It was the upper-left third of something that used to be office equipment, and built the circuit out of a 7805’s datasheet with an extra big capacitor on the generator side. It charged phones. It was jank AF though. All it did was offer 5V at I have no idea how much current on the power pins of a USB Micro-B cable.
Most stationary bikes have a flywheel. You could 3D print a gearing set to run a small generator (like this one or DC) off if it. There are tutorials out there about how to set up it up.
I actually did that with an actual bicycle and one of those “make any old bike a stationary bike” stand things. Harvested an old motor out of…what was it, a printer or something? Photocopier? It was the upper-left third of something that used to be office equipment, and built the circuit out of a 7805’s datasheet with an extra big capacitor on the generator side. It charged phones. It was jank AF though. All it did was offer 5V at I have no idea how much current on the power pins of a USB Micro-B cable.