For a speedometer how about a "drag mouse".  as entering pit lane, drop and
drag an optical mouse along the payment.

For slippage, one optical mouse sensing each wheel/tire.

Bill

Current project is using a pic as the controller for a plotter using an old
Etch-a-Sketch.

----- Original Message ----- 
From: "Bob Axtell" <engineer@cotse.net>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Tuesday, October 19, 2004 8:05 AM
Subject: Re: [PIC] Traction Control / Wheelspeed sensing


> I once acted as a consultant (feasibility study) to someone who wanted
> to design a reliable
> NASCAR speedometer for INSIDE the car (to prevent tickets when going
> into/out of
> PIT ROW or when under YELLOW flag). I installed a few pieces of custom
test
> equipment on a test race car and ran it for a few days. Here's what I
> found out:
>
> 1. The tires wear so rapidly, and changed shape so rapidly, that using a
> fixed mechanism was
> never better than 10% accurate. In particular, the right and left tires
> wore differently, and
> sometimes were deliberately inflated differently.
>
> 2. Since speed is the measurement of the distance per unit time of the
> car going FORWARD
> over the ground, the slippage when the car cornered is significant.
>
> 3. The best (and present) method is to detect the car between posts,
> which provides a reliable AVERAGE
> speed. But that does NOT provide instant speed values.
>
> Along with my mechanical engineer consultant associate, we decided:
>
> 1. No mechanical mechanism would provide a reliable source of speed
> measurement.
>
> 2. Either Ultrasonic Audio or RF doppler "radar" could be used if the
> sensors were mounted under
> the car, and would bounce off the pavement. The reflected signal would
> be frequency-shifted due to
> the pavement. Its like normal radar except that the sensors were
seperated.
>
> 3. We decided that Ultrasonics would be cheaper but RF would be the most
> accurate. The Audio source
> would have to be intense to not be drowned out by the noise of the car.
>
> It was a fun project. But it took forever to get paid....
>
> --Bob
>
>

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