Rims

**DJiK** · 03-27-2006, 02:43 PM

I found another video.

Here's how you'd get power or anything else to the wheels...
I'll try to describe it:
Circular rails... They'd be positioned on a plate, and brush contracts will be touching them as the plates spin.

Picture a rotating circular target. Each circle in the target is a copper contact rail. Now, you're putting a brush-like (or old style key-like) pin with stationary contacts that are touching the rings in the target. Just like a turntable player with multiple needles.

If you only need only two wires (+ & -) then there's really not much to it.
The key is choosing the right components to minimize heat and corrosion so that the contacts stay fresh longer.

**RPI Geek** · 03-27-2006, 03:17 PM

Yes, that would work, but it's not really an option for something that should just be a bolt-on thing. Plus there are issues (like you said) with sparking, corrosion, dirt, interference with the other (more important) things on the wheels like the brakes...

I suppose I could use a transformer of some sort, but I'd really rather modify the suspension as little as possible.

Also, my first iteration will probably go on hubcaps: cheap ones from Wallyworld. Preferably hubcaps that can snap on to steelies. I don't want to go mounting LED's to my nice alloy 5-spokes.

**Fusion-One** · 03-27-2006, 03:38 PM

why not use the power of the wheel rotating to generate electricity? A small DC motor on its side with a weight hanging off the shaft always trying to keep it pointed towards the ground would have the effect of spinning the shaft. I'm sure you could generate enough power to run LED's and a microprocessor.

I have a Powerball which lights up LED's just from your hand movements.. and they light up BRIGHT.

Seems like the easiest way to power the device.. you could have a Li-ION battery for when the car is stationary.

**RPI Geek** · 03-28-2006, 12:18 AM

Originally Posted by Fusion-One

why not use the power of the wheel rotating to generate electricity? A small DC motor on its side with a weight hanging off the shaft always trying to keep it pointed towards the ground would have the effect of spinning the shaft. I'm sure you could generate enough power to run LED's and a microprocessor.

... ...

Seems like the easiest way to power the device.. you could have a Li-ION battery for when the car is stationary.

You're forgetting centrifugal force, unless you mean to align the motor with the hub. That's worth thinking about more...

I'll probably use a Li-Ion battery for the first attempt, and work on the power system later.

**Fusion-One** · 03-28-2006, 12:24 PM

Another suggestion would be to use an LED bar which goes straight across the center.. No hole that way.

**DJiK** · 03-29-2006, 03:24 PM

Originally Posted by Fusion-One

Another suggestion would be to use an LED bar which goes straight across the center.. No hole that way.

Yes but, the resolution/sharpness will be awful near the center because of the low rotational speed.
Plus, on a real rim (not a hubcap), you wouldn't be able to unscrew it without taking the entire LED bar out.

RPI, have you composed a product list (of the thinkg you need to buy) yet?

**gnomad** · 03-29-2006, 05:24 PM

I'd bet they use slip rings for power and a magnetic sensor coupled with a fixed magnet in the frame to determine the position of the wheel. The magnetic sensor generates a pulse train that is used to determine wheel speed and a fixed calibration point.

Similarly, take a look at the Hyp-know-tron: http://www.igi.org/hkt/ I saw this for the first time out at BurningMan 2000. fscking amazing...

-g.

**RPI Geek** · 03-29-2006, 06:23 PM

I haven't done anything for this other than in my head. The way I see it, a lot depends on the LEDs used... physical size (resolution), wavelengths and luminosity of the LEDs (true color or weird colors), temperature tolerances, power consumption, etc.

I just haven't really gone out and looked at these things yet because I have 2 other projects here that I need to finish up before I can start on a new one :/

My first idea was to get a bunch of cheap red LEDs and work out the bugs in the sensor, software, and controller using them. Then I could move up to the more expensive, cooler-looking LEDs.

I'm not looking forward to the Radio Shack bill for this project... Any good online places to buy from? I've never really done a project like this before.

**konnichiwa** · 03-31-2006, 04:37 AM

I'm interested in this project. I would use a Cross + arangement of LED (single color at first of course!), bezel out a bit of my alloy wheel / cover with acrylic for the LEDs, use RF to transmit the picture, and use a battery for the time being, thats out of my scope, i'm not an engineer. I could program a microcontroller with most things that are needed to complete this... I'm not a fabricator so it would be messy, i'd have to off load that part to someone else.

Minium speed would be a factor, however it would only need to be aproxx 20 mph before you had a clear picture.

**Tercel96** · 03-31-2006, 03:46 PM

Remember that any modifications you put on the wheel have to be counter-balanced, or else your wheel is gonna vibrate at higher speeds, causing lots of problems... and balancing wheels is not an easy thing to do...