RC Timing system

[slow]

I would like to build a timing system for rc cars. I would like for it to work off of a light system like drag racing uses. I know the math to calculate the speed from point a to point b, this will be 100'. I just would like to have a system that would do the math for me and also show on a display the speed. I have so experience it building some electronics buy have never took on someting this big.

I would be thankful for any help.

Thanks
Slow

 

[stevez]

Some thoughts/questions:

A. How will the system know when to "start"? Will it be at the same instant the driver is told to go - possibly the "green" light?

B. How will you sense that the finish line has been crossed?

C. If you do the math for the time between start and finish - over the distance you'll get a number but does that get you what you want? In some races the top speed is posted along with elapsed time. Top speed requires more information. You might time the last few feet of the track as a way of establishing top speed.

 

[slow]

I want it to start and stop from some sort of light beam. This way I can get the top speed down the straight stretch as cars go by.

 

[stevez]

Here in the US a common Cub Scout project is Pinewood Derby. I've seen posts here about timing systems. You might google on "pinewood derby timing" to see if you can adapt something that's already been done.

 

[jpanhalt]

I just would like to have a system that would do the math for me and also show on a display the speed. I have so experience it building some electronics buy have never took on someting this big.

Slow

I would suggest getting the timing function done as already suggested. For the speed calculations, I suggest you start with a spreadsheet and a portable PC, if necessary. You can display the results in a graph.

Where are you located? That could make a difference in terms of the sort of components you might have available. For my son's Pinewood Derby, I used simple IR-based switches, switching transistors for interface, and hacked a cheap WalMart stopwatch for the time. That approach would not be feasible, if you do not have access to a cheap electronic stopwatch. John