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Identifying a R/C car

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Let me pick your bright brains for a bit.

I've designed a set of F-1 style race startlights. It uses a laser pointer and photodiode to sense false starts and give audio and visual warnings of them.

I would like to add a timer to this but don't know how I would identify the different cars. I've seen it done by having 4 photodiodes and 4 laser pointers with "flags" at different heights on the rx antennas of the cars, but this is not a solution I'm interested in.

I've thought about color temperature, RFIDS etc., but not really sure which way to go.

Anyone have any ideas how I could sense the different cars?



Edited by mikep
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How about an IR LED on each car that uses a tiny oscillator or pic to generate a modulated light source, with a different frequency or encoded signal for each car.

A photo sensor focused precisely across the width of the finish line would detect the frequency or encoded signal of each car as they passed through the focal point of the photo sensor.

Used on a closed loop track, it could also count and display laps for each car, average speed per lap, etc.


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  • 2 weeks later...

I cant help thinking the with any light system you will get 2 signals together or blocked signals when 2 cars are side by side. I know how well that would go down at my local car club as I used to race there, some people get a bit carried away !

The system we had used transponders on the cars and it was spot on, it could even tell if a car had taken a short cut.



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Hi Bill,

Thanks fior the idea, but I'm not sure about it yet. It would mean I would have to create a circuit for every car that raced with us and I'm not sure I want to do that.

I think I will keep looking for a bit before I decided.

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This is a tough application because the required resolution is so small. I like the RFID method, but like nearly everything else that I can visualize, identifying the winner in a near nose-to-nose finish is going to be a challenge

I would expect each RFID tag will have its on particular performance due to the installation on the model. Keep in mind that a targeting error of just a few centimeters could identify the wrong "winner" in a tight race. A buried wire aerial across the finish line might help. I guess a camcorder could be set up as a backup device if there are disputes. :)

The optical idea from YB2normal should eliminate the resolution issues. You could place an elevated structure above the finish line that contains a continuous row of independently sensed IR detectors (covers entire finish line). An IR transponder on each car would be aimed straight up. However, the reliable performance may suffer if two cars are side-by-side/nose-to-nose (due to the aperture of the IR beam). That worst case state could be an issue.

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