Railway cars & turnpike toll booths use bar codes in the US.
John Ferrell
http://DixieNC.US

----- Original Message -----
From: "Liam O'Hagan" <liam@GLI.COM.AU>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, March 16, 2004 8:04 PM
Subject: [EE]: Identifying cars


> Howdy everyone, a question on the best solution to this particular
> challenge.
>
> I'm a member of a car club, and we often have track days where we're timed
> around a racetrack. Currently the timing consists of people with
stopwatches
> clicking the button when they see a car go past.
>
> Needless to say this is pretty inaccurate and not very reliable.
>
> Recently someone asked me if I could make a timing system, using a
> transmitter on each car (as cheap as possible) and a "beacon" that would
> detect the passing of the car, ans also identify the car.
>
> I've thought of 2 possible solutions and would appreciate feedback on what
> which is the most suitable, and reliable, and whether anyone has any
better
> ideas...
>
> The first solution would consist of an IR led on each car, flashing at a
> discrete frequency, or even flashing a predetermined "ID" code. A beacon
> would sit by the side of the track at the timing marker and count pulses,
> identifying each car in turn. In this case the beacon sees the car pass. I
> thought initially of using a discrete micro on each car, but it would be
> overkill. A 555 based timer would be easier and cheaper...
>
> This has the advantage of being reasonably cheap to implement, and it's
easy
> to have a different frequency or code for all of the different cars (about
> 50 different cars per event, but only 8 on the track at any one time)
>
> Another option is to have an IR transmitter on the beacon, and an IR
> receiver on the car. The car would also have a RF transmitter, so when the
> car sees the beacon pass, it identifies itself via RF. This would be more
> expensive, but I think more reliable.
>
> The range from the beacon to the car would be 5 - 20 metres (15-60 feet),
> depending on what line they take through the corner. Speeds at this point
of
> the track are generally 70 - 120km/hr (45-75 MPH)
>
> The angle between the beacon's line of sight and the path of the car would
> ideally be 90 degrees, but knowing some of the drivers this could vary
> considerably!
>
> The software and timing will be handled by a PC attached to the beacon (or
> communicating to the beacon through RF again) and displaying the times.
I've
> done that part, just need to handle the detection and identification of
the
> cars now...
>
> Any ideas anyone?
>
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