I've tried looking around for as much information as I could gather to build really small wearable electronics that could power themselves by generating energy with movement.
I know that the technology already exists in watches. There are watches that produce their own energy using a small generator that spins when the wearer moves its arm around. The energy is stored in a capacitor to make the watch work quasi-infinitely as long as the wearer moves enough throughout the day so that enough energy is generated. (some info here : http://en.wikipedia.org/wiki/Automatic_quartz )
I have trouble finding information about just how much current can this technique output for practical uses and if this technique can be adapted to work with other electronics.
In spirit of actually having real questions and not just vague stuff, here's a couple of questions I hope can get answered
- How much energy can these devices produce / store?
- Is there any other devices aside from watches that are powered using only kinetic energy?
- Is there any schematics on how to create a kinetic generator for low-power devices?
Edit : Some people have said that it is hard to determine if it's possible since I didn't mention exactly what I would be doing. I don't have any project right now but I want to play around with wearable electronics that are motion-powered instead of battery-powered that you need to replace or recharge.
I'm thinking of using the lowest-power MCU I can find (something like the IT MSP430 microcontrollers) and reduce the current usage to the maximum by using standy mode as much as possible and doing very little active work, maybe just for logging multiple sensor data every couple seconds.
Best Answer
I saw this answer and glanced at my watch, it just so happens to function in the way you describe. There's a large half-disc pendulum inside which presumably is used to collect the kinetic energy. It can run for about let's say one day If I walk about 2-4 miles a day. If I move throughout, indefinitely, but then, watches require very little power to begin with.
Energy Storage How much energy you can store only depends on your capacitors and batteries, etc, it's not inherent to the the energy generation method you want to use.
Other Devices I don't see why you would look at it this way as mentioned before. Decide on what you want to use kinetic energy to power and then do a few basic calculations based solely on first principles, assuming 100% efficiency of kinetic energy -> chemical / electrical energy and you'll quickly see what's doable and what's not. As a general guide, microWatts, up to a maximum of say a few milliWatt is probably all you can do (this very much depends on the type of physical activity you're using, more strenuous activites could very much reach into Watts)
Schematics I can't give you one, but I can tell you the design is very simple. Take the pendulum in my watch mentioned earlier(here's a picture of one from your article):
While I can't specify exactly how thing's work internally, what I do know is this:
"Electromagnetic induction is the production of an electric current across a conductor moving through a magnetic field"
After reading the provided article, the pendulum is used to spin a pinion(visible in the picture) - just a small gear, which in turn drives an electric generator(which has been documented plenty). Anyway, you're likely to get an AC voltage from the electric generator. You can use perhaps a bridge rectifier, maybe a voltage regulator as well and store this in the energy storage device of your choice.
Finally Like I said before, decide on what you want to power first, that's the only way you're going to be able to do this properly. Make an upper maximum required power for the circuit you want to power and proceed from there. Feel free to ask for any more help but based on the information so far, this is all I can do.