I’ve started getting into building circuits, and I’m trying to build a bike light powered by dynamic energy (generated by the bike’s movement). In the old days, there were these clunky dynamos that really slowed your bike down, but LEDs now generate a lot of light without needed much energy to power them.
I was wondering if there were any readily available ICs or any kind of cheap technologies that would be able to capture the energy of movement? I don’t know if this is possible, but in my mind, I see a wire hanging down in the wheels and being constantly battered by the spokes, thereby creating energy somehow. Is this possible or is this a pipe dream?
You could just attach strong magnets to the spokes at regular intervals, then position a coil of wire so that the magnets pass it fairly closely as the wheel rotates - this isn’t a lot different from a conventional dynamo, except that it uses mechanical parts that already exist on the bike.
Or you could just use one of those clunky dynamos - they won’t slow down your bike so much if you have a smaller load attached - the braking effect is largely due to the load on the dynamo.
There’s no IC that will do this, although there ICs that are designed to efficiently manage the power generated by the transducer. The problem is that there isn’t enough energy available through “energy harvesting” to run an LED. Even though LEDs are more efficient, you still need a Watt or more of energy, which is far, far greater than current energy harvesting devices can generate.
I’m not sure what you’re looking for. Those old dynamos might look clunky, but they were efficient. And, because LEDs are pretty efficient as well, you ought to be able to store and use the generated energy for a long time.
I could see trying some other method of generating power – like putting magnets on your rim and having them pass through a coil to generate current, but you have to be sure that it won’t interfere with your braking capability. Getting a dynamo is probably a lot quicker and easier.
You could always stick solar cells and a storage battery on your bike.
I’m not sure if there’s a practical way to do this other than the tried and true method of moving a wire through a magnetic field (e.g. generator, dynamo). You could perhaps mount magnets around a wheel rim and coils near the rim.
I’d be surprised to hear there’s any sort of magic IC to do this. What physical principle might it employ?
ETA: Obviously, it took a while for this to post.
Modern hub dynamos (the dynamo is built into the hub of the front wheel) are much more efficient than the bottle dynamos which rub against the tire that I think you are thinking of. Coupled with LED (or Halogen) headlamps, they make a very nice, albeit expensive, bicycle lighting system.
If I ever put together a purely commuting bike, I’ll likely go this route. For now, I have a battery powered HID (High Intensity Discharge) headlamp. A very nice, but hugely expensive, lighting system.
A simpler way might be to use rechargeable batteries and just recharge them at home. And the light will shine or flash even when you are stopped in traffic. Not to mention that these are already sold commercially and would save you a ton of trouble.
The military has spent a boatload of money performing research in the area of “energy scavenging.” The goal is to place sensors around an aircraft that do not need wires or batteries. Much of the research has looked into ways to scavenge energy from random vibration. The obvious problem is that very little power can be extracted from vibration. Not sure what the status is on this research.
IMO, **sailor **has the best answer. A COTS battery operated device will be the most reliable option.
This is a year-old thread. But I’ll just mention that modern dynamo hubs have imperceptible drag, and are more reliable than battery-powered lights because there’s no danger of you forgetting to charge the batteries. And some of the lamps designed for hub dynamos have a “standlight” feature, where a capacitor keeps the light on for a few minutes after you stop.
I have to wonder how reliable that connector is. If it’s not properly sealed it will be very susceptible to fretting wear & fretting corrosion. I would rather have a sealed battery-operated unit.
It’s very reliable, in my experience and from what I’ve heard. Fretting doesn’t seem to be a problem, as the wire is very light and is secured to the fork. The holes on the connector (which the wires go through) are “sealed” with a dab of grease - crude but effective.
There are a few of the generators that rub against the wheel. They usually spin a cylindrical magnet that has four poles around its periphery, N S N S, every 90 degrees another pole. Then there’s a U-shaped steel bar that covers the two N poles (looking at it right now, say), and another that covers the two S poles, and a rod joining the two steel bars, and a coil around that rod. Very simple.
I think the best thing is to get one of these little battery-powered lamps you strap onto your leg just below the knee. It has a white light looking forward and a red one looking back. Nobody in their right mind is going to run over something with a single glowing 1" diameter eye hopping up and down in the road.