Power generation for car rotating wheel hubcap

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I am looking for a way to get rid of battery for a small AVR board mounted inside of a hubcap or aluminium alloy inside of rotating car wheel.

I am not able to mount anything on the fixed side of the car, only inside of rotating wheel. Also, it would be ideal if it could mechanically fit into hubcap center since it would eliminate balancing problems on high speeds. I need to power AVR only when wheel is rotating.

I have seen some hand lamps that work for a while after you shake them well. Could some variant of this be applied? I was googling around but I guess I was not using good keywords. Are you aware of some helpfull links that you could share?

I have big doubts that this goal can be achieved by the hobbist, but again, if hope didn't exist you wouldn't be reading this.

All ideas are welcome! :lol: :roll: :lol:

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Good suggestions will be dependant on the power required, any clues?

Yes I am getting grumpy!

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In principle, you can put a fixed magnet and then a (moving) coil in your PCB. Rotation will generate an AC current flowing trhoug the coil, thus you would have an alternator (I don't know if this is the right word in english).

All this require some experimentation, protection against high voltages, and a minimum RPM to have something. Also it depends on the power consumption.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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A little stepper motor with a pendulum. Steppers are great generators.

Imagecraft compiler user

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I think Bob's idea is the way to go. There was a thread here not too long ago about getting power to a rotating shaft without using brushes, and it got me thinking about building a generator sufficient to power an AVR. It turned out to be quite easy, and it produced +/- 10v using a small fan motor.

I don't know how fast you would have to be driving to produce sufficient power for your application, but it would be easy enough to experiment and find out.

Yes, my pathetic thing is extremely ugly, and yes, that is a lot of glue. But it was fun. Bob's idea of using a stepper motor didn't occur to me or I certainly would have gone that route. Thanks, Bob - good tip.

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Chuck Baird

"I wish I were dumber so I could be more certain about my opinions. It looks fun." -- Scott Adams

http://www.cbaird.org

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Quote:

I am looking for a way to get rid of battery for a small AVR board mounted inside of a hubcap or aluminium alloy inside of rotating car wheel.

Quote:

A little stepper motor with a pendulum. Steppers are great generators.

So someone figured out with this patent:
http://www.patentstorm.us/patent...

[Try this starting point: http://www.reuk.co.uk/Stepper-Mo... ]

Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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I did some thinking about this a year or so ago. A colleague of mine wanted to install a video camera and recorder inside the blade of a wind farm turbine, and needed a way to power it. But a car wheel is rotating much faster (I think), and an eccentric weight on a stepper might take off and start to spin with the wheel at higher speeds, throwing the wheel out of balance. Would a conventional DC motor be less "sticky"? Could you use some clever power regulation scheme to better cope with the range of speeds?

Four legs good, two legs bad, three legs stable.

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At 60 mph a 16" wheel is rotating about 21 times a second, so I don't think there's any doubt the stepper and weight would spin. You can see it in the spinning hubcaps that are popular - the car doesn't have to be going very fast before the spinner simply follows the wheel (although of course they're not weighted in the same way we're talking about). However, like the hubcaps, the effect may be sufficient if it only happens when accelerating or braking.

Chuck Baird

"I wish I were dumber so I could be more certain about my opinions. It looks fun." -- Scott Adams

http://www.cbaird.org

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I really don't know nothing about physics, but in my car, I have those "ligth" wheel interior (I don't know the name in english), and these wheels are calibrated everytime I change tires. The calibration procedure consists in putting a small weight (a fews tenths of grams I think) in the said part. Someone "explaned" me that if the wheels are not calibrated, the car kind of seems to loose control when at higher speeds.

So... what kind of wheels do you have and where exactly are you going to put that extra, potentially dangerous, weight :)? Maybe someone can enlight me on this...

Embedded Dreams
One day, knowledge will replace money.

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Expanding on Nuno's concern, if the necessary pendulum has significant weight and begins to rotate
to follow the wheel it will appear as a significant unbalance which will affect control of the vehicle.
Consider this effect occurring with four wheels at slightly different rates, a harmonic convergence
could be disastrous.

To maintain wheel balance and generate energy consider a coil/stator assemblies mounted on the
inside of the wheel rim with associated magnets mounted on the wheel spindle plate assembly.
Another method would be to use the interial mass of the balanced hubcap to drive a generator
mounted on the wheel. This would work for stop and go traffic, not at constant speed.
Both of these solutions require significant mechanical engineering.

Stan

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How much power is needed again? Could you beam a couple of mw at a couple mhz over to a tuned circuit and a diode? Isnt this how RFIDs are powered?

Imagecraft compiler user

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First I must apologize to everyone since it was not my intention to make such a late reply. Unfortunatelly I couldn't reply earlier. I must also thank everyone for your ideas. I didn't expect so many answers.

@bitbasher:
MEGA16 and 16 leds, optionaly with RF radio link for central remote control.

@Guilem and others:
I am limited with access only to hubcap or whole rotating part of the wheel, so nothing can be mounted on fixed part of the car. Available area is only the wheel itself. With that limitation, I think that alternator and steppers can not be used.

@theusch:
If eccentric weight is used with stepper, it looks that power could not be generated constantly. This might be a problem if there is only little acceleration/deceleration.

@Nuno:
I am aware of balancing problems. My device would not be heavy, but it would be enough to spoil wheel balance and it would be hard to calibrate it in a usual way of putting small weights where needed. However, all this can be solved if device is attached to wheel in only one spot - the center of the wheel. It's not my idea. I have already seen a working device attached in such a way to a wheel.

@bobgardner:
Interesting idea. I know that 125kHz RFID passive tags work the way you said, but actually that's all I know about it. Do you think that some device located in fixed part of the car could generate enough power to have my devices in 4 wheels working constantly? Could that interfere with car electronics? Could you please give me some URL so I could learn more about this method? Does such power generator already commercially exist so I could buy it and just concentrate on receiver?

Btw. I would need AVR constantly powered at least in 10-60 km/h speed range. That is about 2-12 revolutions per second.

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Mad, off the wall idea #37:

Solar cells and a small rechargeable? ;)

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@clawson:
AVR device will be powered only at night so it would have only one daily charge ready for the night. I could live with that if it could last at least 20-30 minutes. What concerns me more is that car wheel will be a hostile environment for a solar cell. It could easily be damaged, broken, or get too dirty to be functional. Maybe there is a way to mount it and box it safely? Up to now I am not aware of it, but that doesn't mean that someone else can't figure it out :roll: .

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Do solar cells still work even if protected behind something like a sheet of perspex ? (or does it filter the range that is delivering the energy?). But I guess this doesn't solve the "dirty" problem.

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An other possibility could be a peltier element. These parts generate electricity if there is a temperature difference between the two sides of the element. After hitting several times the break, there might be enough power available for your application.

http://en.wikipedia.org/wiki/Thermoelectric_cooling

Regards
Sebastian