Chris,
good point, but having now done some more research IR seems to be the system
that everybody uses.  I suppose the probability of the signal being
completely blocked is fairly minimal, so a missed lap is considered
acceptable.
I did consider using a radio transmitter/receiver system but I don't believe
the signal can be focussed down to the point where the car crosses the line,
or can it??

Mark


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of chris hornby
> Sent: Thursday, March 11, 1999 12:52 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: lap timing project
>
>
> >
> I have managed to find a couple of circuits, but the range is
> limited.   Any
> ideas what defines the range, is it the performance of the IR
> components or
> the circuits driving them?
> <
>
> Is their not a danger of it screwing up if the IR is blocked by
> another car passing between you and the pitwall. are their any
> other options beside IR?.
>
> CH.
>