Help with timing curcuit

[martini]

Hello, I am looking for a way of timing a model from one end of a track to another. I will be purchasing a Phidgets 8/8/8 interface for another part of the build (it is a windtunnel). I was wondering if there is any way of using this to time the model as it rolls along the track, or whether I need to look at a different setup, but I have been looking into using light gates and the things seem to be rarer than hen's teeth, so no such luck their either. I could use a contact on each end of the track so that when the current at one end is broken, the stop clock should be started and then when the model reaches the other end of the track, it will allow a current to pass through, thus stopping the stopwatch, but I have no idea how to control said stopwatch, or what stopwatch or other equipment I would need for such a setup.
Any help would be greatly appreciated, as I am in a bit of a pickle...
Thanks

P.S. The Phidgets interface has both analogue and digital inputs and it also has digital outputs, I'm not sure if this information helps at all.

 

[GreenGiant]

we are going to need a little more information to help you out.

How wide is the unit you are trying to measure?
How fast will it be moving?
How accurate do you need to be with your measurements? (seconds/milliseconds/microseconds?)
Do you have a lot of room around the track?
Is the model secure on the track and does it travel exactly the same every time with very little side to side motion?

 

[martini]

Ok, yeah sure, sorry, I wasn't sure what information you needed...
The unit I am trying to measure is about 30mm wide, and will be moving between 0 and 7 MPH, I will need to measure to milliseconds, but microseconds won't be necessary.
There will be a lot of space around the track if I can route the cables outside the wind tunnel (150mm), otherwise there will not be much room, as the windtunnel is 360mm x 360mm, and I need to be careful not to interrupt the airflow.
The motion of the model on the track will be the same each time and the model cannot move from side to side, but it doesn't have anything holding it down on the track. The track will be about 500-900mm long.
If there's anything else, I will do my best to answer any questions...
Thanks a lot!

 

[CDRIVE]

LEDs and Phototransistors are very inexpensive. Combining the two as Set/Reset elements is usually easier to do, (both mechanically and electrically) than switches or other means. Best of all, they're fast!

Chris.

 

[martini]

Thanks CDRIVE, that sounds like a good idea, but I have absolutely no idea how to go about it... Sorry for being so useless, I am by no means an electronics expert, amateur is pushing it... Thanks!