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Bike Lighting - Pedal-Powered 60W Incandescent Bulb? Answered

I know, I switch projects a lot. I just can't stay focused on one thing for too long.

Anyway, here's my idea:

There's a local museum called Fort Discovery, which, by the way, is quite cool. But, there is this exercise bike they have there, and connected some how (I haven't been there in a while) is a few different home tools, like an incandescent light bulb, a drill, a hair dryer, and something else. There are switches, so you can turn whichever ones you want on, to see what you can power. The "exhibit", if you will, is to show how work = power. Now, I'd like to try to hook something like this up, except a few things will be changed:

  • It would be a regular, moving bike.
  • There would only be a light bulb.
  • I want the power to be stored in a capacitor, because what would be the purpose of having a light while riding in the daytime?

Now, besides from the point of me not knowing at all how to hook this up, I wonder if there would be a capacitor that would store enough power to light the bulb for a reasonable amount of time, if say, I used a 60 watt bulb. Then of course, I have a few questions, some of which I may of already said:

  • How big would the capacitor have to be hold enough power to light the bulb up?
  • How many hours (or minutes, if applicable) of moderate riding would it take to store enough power to light the bulb enough to see for about 15 minutes?
  • Would the power stay in the capacitor so that I could charge the bulb a bit over the course of a few days?
  • How would I hook such a circuit up?
  • Could I hook the circuit up so that the power is stored from the wheel going around, rather than my pedaling?

Thanks for any and all help, and if this turns out all right, then I may just put an Instructable up. I guess I'll have to see. Thanks again!


. I'd try starting with something like the systems that have a generator (not an alternator) that is driven by one of the wheels and add a capacitor in parallel with the generator. You'll need a switch to isolate the capacitor when you're idle. Basically, all you're doing is replacing the battery of a simple battery/lamp circuit with a generator and capacitor. . A low-leakage capacitor will hold a charge for long time - weeks or longer. . I think a 60W bulb will be way too much. I'd use LEDs - much more efficient.

Thanks, that helps a bunch. So, I'm basically building a self-powered generator, storing the power, and using it. Let's think maybe of a more realistic goal - remember those speakers? Instead of batteries, I'll try pedal power. Do I need to buy a generator, or is it possible to build one? *Edit while Posting* Wow, there's a lot of people on the Internet who have built these, but they are like the one at the museum. No capacitors, no movement. They seem to be using a bought generator. The generator hooks up to the stand, and the bike spins it. Makes me wonder why no one has done this on a mobile bike. Thanks again.

Makes me wonder why no one has done this on a mobile bike.

Stop in a bike shop and ask for a friction generator light ;) They have been around for awhile - the only drawback of not having a way to store energy is that when you stop (at say a traffic light) - you don't have any lights, so other vehicles may have a hard time seeing you....

. It's possible to build a small generator, but it would probably be much easier to buy one. Might be able to find one at a flea market. One of the small ones specifically designed for bicycles should be cheap and may have the light included.
. A capacitor that will drive a small amp or large lamp for more than a few seconds is probably going to be large and expensive. You may be able to find a "super cap" that will work for longer.

There's a 'supercap' LED light project or two on ibles, they'd be a good start...

Regarding the generator, as NachoMaham says, there are lots of 'premade' bike generators available.

1) Most small perm magnet DC motors also work as generators.

2) Check out the Wind Turbine ible--could you fashion something similar on the bike sprocket?

Years ago, my physics professor did a demo on capacitors and how much power an incan. bulb requires. He charged something like a half a farad capacitor bank -- and lit a 60W bulb with it.... The bulb went out in about a second. Careful with supercaps --- they're easy to destroy with voltage.

. PS: Not sure how to size the capacitor, but I'll bet you'll need a huge one to drive a 60W bulb for 15 minutes.