Regenerative Braking Charges Your Phone

Way back when, if you wanted lights on your bike, you’d head off to the local bicycle store and purchase yourself a bottle dynamo. This would consist of a magneto that was attached to a bracket on the back of the bike and would rotate by rubbing against the rear tire, generating power for the lights. These fell out of favor over the years as batteries got better and cheaper and people grew tired of the increased drag and maintenance required. Despite this, the idea of generating power onboard a bicycle has never really gone away, and [Javier] has decided to have a crack with his imPulse project.

The formerly popular bottle dynamo had one advantage over contemporary models located in bicycle hubs – they were geared down to allow the generating device to make multiple turns for each revolution of the bicycle wheel. This is useful to allow the generating device to operate in its ideal range of rotational speed. Going for a more modern take, however, [Javier] has decided to leverage a stepper motor as his generating device of choice. Further taking advantage of modern technology, the imPulse system is designed to fit on to the caliper mounts of modern bicycles with disc brakes, allowing easy fitment while also leaving room for a geared-down drive.

[Javier] hasn’t just stopped at power generation, however – there are also plans for lighting systems and power distribution to enable the generated power to be used for a variety of purposes. It even has turn signals – though that’s not the first time we’ve seen them on a bike! Video after the break.

17 thoughts on “Regenerative Braking Charges Your Phone

  1. Nice project, although I do not really get the improvement of a stepper motor over any other kind of DC-motor or perhaps a standard dynamo (which is actually geared up, as it must make more turns then the wheel driving). I’m very confused about reading that hub-dynamo’s (the ones embedded in the wheel) produce drag. The amount of drag is only noticeable when drawing current. Something easily solved with a switch… hmmmm. Since these dynamo’s don’t use a gear or rub against your tire, the losses in “gearing” are virtually non existent. I can’t see how a motor with some plastic gears be an improved over “drag” and more importantly an improvement over reliability. Because we will all agree, light on a bike are essential and must be able to function at any time (although during the day you’ll get away with non functional lights).

    HOWEVER: I won’t bet my life on people noticing the indicator light. It is a fun add-on but chances are that it will only confuse the people driving up behind you. So please look left and right over your shoulder, stick you hand out, look back again and then carefully make the turn.

    Regarding light being put directly under the saddle… make sure you are not blocking it with your coat (or bag).
    It happens all the time here, during winter so see mysterious pulsating red glow in the distance… as you approach it becomes clear… the red glow is coming from underneath something… as you approach even more… you notice that the red light belongs to a biker who wiggles his ass left and right (from paddling the bike) and while doing so obscuring/revealing the light from the rear. For those people I would like to say: mount lights where they are supposed to be mounted… on the mudguard in clear sight and away from any possible obstruction. So it is better visible from the sides as well.

    Regarding this project, I wonder about the visibility from the side, perhaps some LED’s on the side could be added but a nice reflector combined diffuser would be better. As it would guarantee visibility even when the electrical system fails (which will eventually happen everyone with a bikes knows that) AND it prevents other people from being blinded. Some sort of covering is required anyway, one day in the rain with that open construction and damage starts happening as the reliability of the digitally controlled LED matrix WILL let down (I wanted to say “LED” as it would be a nice pun, but I didn’t).

    Many bike light related projects have gone by over the years all with the best intentions. Some people even mount freakin’ lasers onto their bike. Just imagine how the road would like like with all those various kind of lighting systems, do you think your safety improves by distracting the attention of approaching drivers? I guess we all know that there are rules/laws for bicycle lights, intended to ensure for better safety on the road. Hacking your own X-mas lights onto your bike is not something that goes hand-in-hand with public safety.

      1. Jesus, what a text! I mean, 44 words, really?. Please understand that this is a hacking website (hack-a-day, remember?) and not Reddit or Twitter or Facebook; what is rule in the roads of your local traffic may not be in mine, and so on.

      2. 521, hmmm that’s almost twice as long as the article… you are right, I should have put in more effort. Perhaps concentrated more on the hub dynamo, as I felt that this article did great injustice to that technology. Or perhaps more about safety? Because shouldn’t hackaday have some sort of obligation to their public regarding to safety or technical correctness?

        Because we all know that lot’s of readers come to this site and learn something from it. Hackaday is aware of that and therefore produces small articles that teaches them/us how to do certain things or how certain things work.

    1. Actually if your coat hangs over the seat much you can be trapped in place when making a normal dismount as well in a panic. Ski jacket length, your legs need the room. I ride in winter too.

      I find the seat post height is better at visibility, most motorcycles and cars have a higher than axle level rear light. Then there is that third brake light, way up at eye level. The lower looks farther away in diffused or poor light.

    2. I’m partially agreed on the indicator aspect. Other road users don’t expect to see a red dot matrix display acting as an indicator. Moped indicators on the other hand should work quite well since they’re the right colour and go in the right places. The problem then is getting 12V on a bike. Dynamos generate about 6V, ebike batteries run in the 40-60v range. Getting a tiny bit of current at 12V should be possible with DC-DC converters but I haven’t found the right chip for say 5A at 12V which I’d want so as well as indicators I can have motorbike head and tail lights.

  2. No back brake? Yikes! Watch out for sand bars. Don’t brake hard in turns. Safety in redundancy.

    Animation on turn signals OK, but use the whole frame not just half. Animation on brake light dumb, maybe a short strobe followed by full light. One big LED in a focused setup would be a lot better on the front than a non directed array, and weigh less. Headlight cannot be used as turn signal, they need to be separate.

    A bottle generator can provide only enough current to light a 400mA or higher rated LED safely without anything but a diode bridge and a cap. Full light at a walking speed! None of that messy regulation and support circuity needed, KISS! A zener diode is an energy sink, not a way to regulate power where the word is efficiency. The generator slips magnetically when it’s maximum current is reached, no waste of further pedaling effort. More LED’s can be run in series, but full light occurs at higher speeds. The voltage is sorta unlimited towards several times above the original light bulbs design, current is not. The higher the voltage the higher watts out which can be more than 3W but that only comes at higher speeds. They maxed out the generator for reasonable cruising speeds. All this satisfied according to a German law that caught on worldwide.

    I never bothered to turn the light off in the day and of course I never had to remember to turn something off or face a drained battery.

    1. I’ve not seen anywhere that says this replaces the back brake – just that it uses the mounts.
      In the photo it appears to be mounted below the disc brake calipers but at the same location so using the lugs as a ‘stop’. The disc brake still appears to be mounted and cabled up (okay, ‘hosed’ up as they’re hydraulic disc brakes).

  3. > These [bottle dynamos] fell out of favor over the years as batteries got better and cheaper and people grew tired of the increased drag and maintenance required.

    You never tried a hub dynamo, did you? IMO infinitely better than bottle dynamos and than batteries too.

    And this is from someone whose primary method of transport is the bike (work and leisure: regularly did vacations on bike, 2000km/four weeks, tent, cooking and all that. And oh, the dynamo charges the power bank for the camera).

    1. They even make hub dynamos for the people like me who prefer to use 15mm thru axles on the front fork (with hydraulic disc brakes), and not those old style quick release axles. I was just a bit surprised when i saw how heavy these things are, 500g just for the hub, seems a bit excessive compared to the 150g hub without dynamo.

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