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Pinewood derby car mph calculation device

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change1

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I want to build a pinewood derby calculation device to measure how fast the car is going? I want to start the clock when the car takes off, and stop the clock when the car reaches the end, and do the d/t = speed. What electronic circuit can I use to do this? 555 timer? 8 bit micro? any help would be appreciated.
 

MikeMl

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...What electronic circuit can I use to do this? 555 timer? 8 bit micro? any help would be appreciated.
Since you want to measure speed, you can do it indirectly by measuring the time between two sensors. Unfortunately, it takes a division to convert the time of flight to speed. A micro with an timer/counter would do this, but you will have to code a division.

For an application like this I would be inclined to use an old DOS-only laptop I bought at a garage sale for $2. By hooking the sensors to two pins on the parallel port, I would code a speed display using QuickBasic.
 

Dean Huster

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I'm building a 4-track optical system that determines first, second, third and fourth place. Track timers are next. I don't see the need for the arbitrary "mph" measurements when you have the actual track time.

Dean
 
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