RattleGen, to Power Your Bike Lights.





Introduction: RattleGen, to Power Your Bike Lights.

About: Tinkerer from childhood on. After my retirement, together with my wife, fully committed to creative production. I prefer simple solutions for non-existing problems.

The RattleGen is a kinetic electric generator to power your bike lights, for example.

In my search for a dynamo- and batteryless bike light, I found only 2 brands working on the same principle. I had to come up with an other idea using the movement of some bike parts.
Playing with coils and magnets I discovered a new phenomenon. I toke a mechanical relay and put a strong magnet against the iron around the coil. By pressing the contact lever I changed the magnetic flux inside the core of the relay and induced an electric pulse inside the coil. First I used a small 12 volt relay. Later I used a bigger relay and placed the strong ceramic magnet directly agains the coil. The pulse that came out by tipping the contact lever was about 30 volt. A LED was flashing with a serious amount of light. The RattleGen was born. A nice feature is that the linear movement is only 1 mm. I never saw this principle used for vibrational energy harvesting, but I don't know all. The power output of the RattleGen is quit high.
So, how to make this RattleGen useful for my bike lights? The best is as light and generator are placed in the same lamp housing. In this project I show you the prototype and the way I solved some construction problems. The linear movement I get from the spokes of the wheel, near the rim. A lever hits the spoke and that movement presses the contact lever of the relay. I didn't try the profile of the tire as vibrational source. The video instructable show's you how easy the RattleGen can be made. To get the same relay as I used can be hard. The few other accessories you can find in most electronic parts shops.



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    18 Discussions


    1 year ago


    In Montreal we have rental bikes called Bixis (https://montreal.bixi.com/main.php?l=en). They are equipped with lights that flicker when you roll and the bikes makes a peculiar rattle sound. Something tells me some kind of rattle generator is under the hood of this. Very interesting post by the way!

    it could generate power off a windmill or a small waterwheel...would be fun to have a small windmill that lit up different lights depending on windspeed.

    Using the spokes is maybe not the best example for using the RattleGen. I think there are enough vibrational places on the bike to tap energy. For example the profile of the tyre. Rolling a small wheel over the tyre will do. 1 mm movement is enough to induce power. All has to be optimized for that. My aim is to combine generator and light in the same lamphousing to tap contactless energy. So, without rattle...

    2 replies

    You could use an eccentric roller, i.e. with the hub offset from the center, thus it would wobble up and down.

    I would help if you moved your text line up a bit, the youtube pop-up control blocks it.

    I found this a bit disapointing. I thought frame vibrations would cause the rattle. This seems like it would over time damage the spokes or lead to a less true wheel. How is this an improvement over the equivelent dynamo on sidewall approach?

    1 reply

    I love this design, I'm going to have to tinker a little with this concept. Just wondering, if you moved the unit closer to the hub of the wheel would it reduce the rattling? the spokes then wouldn't be hitting the wheel as fast (might make it quieter), but your switch device wouldn't be actuated as quickly. Would changing the time that it takes to flip the switch reduce the flux? Maybe not, since it's a switch rather than a loop continuously changing loop...

    1 reply

    That's exactly what it is; a concept to tinker with. The speed of opening and closing 'the switch' is important. Faster switching generates more flux, more power. An idea is to change the lever for an 'iron fan blade' passing the relay/magnet with a narrow gap. You can mount this to the hub. The rattling is gone because the contactless switching.

    Do you think that you could make one powerful enough that had a large counterweight that would move with vibrations on the road. Basically build the same thing, a coil with a magnet that just strapped to the frame an moved with vibrations. You could use a transformer to boost the voltage from the tiny vibrations. I wonder if you could build one that managed to keep the batteries topped up.

    Hi! Wonderful project. I'm wondering if you have any idea of how this works? Do you think that the vibration of moving the relay contact is moving the magnet slightly with respect to the coil, thus generating a voltage? It looks like the magnet is pretty stationary. Or is a pulse being generated by allowing the magnetic field to collapse when the circuit is shorted? My intuition tends to discount this idea as I always thought you need to have relative motion between the coil and magnet to make generate power.

    1 reply

    Thank you, I am very pleased with this questions because they touch the core of this project. Many people stuck in the application but not in the principle of the electric generation. Yes, the whole is solid state except the relay contact. Opening and closing the magnetic flux gap by this contact lever induces electricity in the coil. To my opinion, and some experiments with a magnetic field card, 'sucks' the iron core nearly the whole magnetic field. The contact is attracted to the core. Opening and closing the flux loop is doing the job. So, no relative motion between magnet and coil, but changing the strenght of the magnetic field through the coil by the use of iron. May be the part of the magnetic field beside trough the iron core has also some influence, I don't know. I am still investigating the RattleGen to find new ways of 'magnetic field modulation'. This different from the common way of moving the magnet compared to the coil or the coil compared to the magnet.
    I hope more people on Instructables pick up this kind of more fundamental stuff as generating electricity in a durable way. Can you imagine, no battery's anymore in small devices?

    WOW! Very interesting!
    Makes me think of the "shake to charge" flashlights. But here the magnet is stationary!
    I've been planning to build those "shake to charge" flashlights with kids in a workshop, but it was either to expensive (available kits) or to hard (for kids aged 6 to 12)
    This could be a simpler alternative.
    How do you avoid the voltage becoming to high for either the capacitor or the LED? Or does it actually stay low when there is a load and do I see a "Joule Thief" on the board?

    1 reply

    Hi masynmachien. I appreciate very much your kidsworkshops. Taking a magnet, coil, diode, capacitor and LED, you can explain them the basics of electricity, the corner stone of our civilization. When using a capacitor the voltage peaks are smoothed. Yes, there is a Joule Thief on board. I was experimenting with this. During the voltage peaks the JT was working and did the LED light up, very bright. As said, during peaks.
    Some research is required to come to a continuously working of the JT.