Persistence of Vision on Automotive wheel

[Wax-um]

Im toying with a new project of using POV on a car wheel to write text or image while car wheel is rotating. For simplicity reasons I want to prototype with a stand alone power supply such as battery and some sort of device to measure wheel speed "all componets mounted to hub cap or center cap". Im using PBP and 16f877A.
My concerns are finding a way to measure the wheel speed interegrated into hub cap or center cap that doesnt require any sensors mounted to car at all. The other concern is will the wheel spin fast enough for the eye to catch the image????
I posted a small post on this earlier about the wheel speed sensor but thought I should elaberate more.

[Archangel]

Im toying with a new project of using POV on a car wheel to write text or image while car wheel is rotating. For simplicity reasons I want to prototype with a stand alone power supply such as battery and some sort of device to measure wheel speed "all componets mounted to hub cap or center cap". Im using PBP and 16f877A.
My concerns are finding a way to measure the wheel speed interegrated into hub cap or center cap that doesnt require any sensors mounted to car at all. The other concern is will the wheel spin fast enough for the eye to catch the image????
I posted a small post on this earlier about the wheel speed sensor but thought I should elaberate more.

OK I see what you are wanting to do. Have you seen those wheels that look as if they are not turning when they are and spin when they stop? a weighted magnet free to spin on the hub rotating around with a reluctor and coil should give you the signal you need.

[Wax-um]

OK I see what you are wanting to do. Have you seen those wheels that look as if they are not turning when they are and spin when they stop? a weighted magnet free to spin on the hub rotating around with a reluctor and coil should give you the signal you need.

Humm??? Interesting approach but not sure if i can do that mechanically???

[Archangel]

Do not know where you are but here in L A taxi cabs have wheel covers with advertising that stays right side up using weighted covers on bearings.

[locko]

I was thinking of trying this one for a future project...
After a few day dreams, I was leaning towards not tracking the wheel movement but use an independent rotating fan type thing that I could control. Different wheel speed and acceleration would make it hard to get a clean looking image. You will have to monitor the stability of rotation before turning on the graphics.
It would be much better to go for a weighted hub assy and then control the rotation of a motor/blade. it makes no difference if the vehicle is accelerating or slowing. You can even be stationary and show the graphics.
I have not gone any further than this basic idea, so not sure how I would make such a device, I just know it would be an easier and more robust way to go. There are plenty of examples of fan type POV out there to get some usable code going.
Just my 2 cents.

Good luck how ever you go with it!

Paul

[Ron Marcus]

For wheel speed, a strain guage with a weight, set slightly off center, will be a pretty linear indication of wheel speed. A modulated LED at a certain point in the wheel well, and a photodetector on your device will give speed and angle of the tire. The LED can be powered from the car battery, or a small battery pack.
HTH, Ron