The project electronics have been very straightforward so far. I used two DC-DC converters shown below with the treadmill, and both worked perfectly. However, when I switched the same electronics to the bike generator, both stopped working abruptly. I think this is because the bike is a lot more efficient at converting mechanical power to electricity and overpowered the converters.
This is a good problem to have! I have a few possible solutions for this, the easiest of which is of course, to go with higher power converters, but this can get expensive. Another way might be to introduce a battery stage before the DC-DC conversion, with a battery charge controller. However, I don't want the project to be limited by needing a battery to work, since batteries are expensive and a bad investment as they decay rather quickly. So, I might burn off the excess power with a passive load, like LED strips or a heater block. Anyway, happy biking!
The primary issue with the ineffectiveness of the treadmill as a means of harvesting human power is that you have to PUSH against something to make the belt move. This means that the upper body is engaged as well, rather needlessly, pushing against the hand rails.
I tried to fix this by setting the incline as high as possible, but still, the friction of the belt was too high and I had to push against the rails.
Since I am a road cyclist having done a couple 100K rides, I know all too well that cycling is one of the most efficient forms of extracting power from humans. So, I took the treadmill motor out and made a bike trainer with the same electronics.
I'm still finding that it's too difficult to power the TV, and at this point, I'm fairly certain that the issue is the motor. It's simply not efficient enough. So, the next steps will be to try out different motors, and make the bike generator more efficient.
This project started out with the history and philosophy of all places. I watched this video about the origin of treadmills. They were invented as a form of extracting labor out of prisoners, and the 'treadmills' powered literal mills, which is the origin of the term.
Separately, I saw a kind of poetic beauty in the idea of modern society being enslaved to 'screens', and loving in a prison of our own making. So, I sought to combine the two ideas. Viola! 'The Treadmill Powered TV' simply run on the treadmill to generate the power for your TV. The perfect way of getting into shape.
I liked the concept even more, when I realized that in a battery-less system if you stop running, the TV would power off, and it would take a minute for it to boot back up. So, the device incentivizes keeping a steady pace- something I struggle with while running. Plus, no battery means practically infinite lifetime(the limiting factor would probably be mechanical or the electrolytic caps in the electronics).
After I made 'The Treadmill Powered TV', I realized that it's a little impractical and inefficient. And the project is slowly morphing into a 'Human Powered Off-Grid Power Generator'.