1/ 100th second Slot car Timer

[Snap]

Yes the projector is for the rest of the racers to see. It will display the real time race times and laps for each lane. There are a few programs out there that simply rely on the printer port for a on or off switch set up with light detectors and a bank of light over them, But the windows timers are not very accurate as far as timing go's. I am just trying to do this myself to see if I can improve on it. I need to time 2 cars and need a way of manually stopping the timers when there is a crash. I am just starting and will work these details out on my own I just needed a starting point. Should the 1/100th second timing be done on the pic and sent to the PC or should the pic only send a signal that the light has been tripped and do the timing in windows. VB does have a few different ways of timing so maybe one of them is better. If the pic and serial port can handle a real time 1/100th second update I will use it for timing if not I will only use it to start the windows timer.

[mister_e]

Any windows will be accurate as long as you can do software calibration... not much.

But the PC interface is a pretty nice option... on the other hand... it may need calibration as well...

[skimask]

Yes the projector is for the rest of the racers to see. It will display the real time race times and laps for each lane.

What I mean is...the spectators aren't going to be able to see the difference between updates every 1/100 of a second or 1/10 of a second anyways, so why not slow the updates down a bit. Let the PIC keep track of actual times down to whatever resolution you want, but only send them to the PC every 1/4 second or so.

I need to time 2 cars and need a way of manually stopping the timers when there is a crash.

Is the timer stopper also going to cut power to the track? (I'm assuming these are the powered type slot cars)

If the pic and serial port can handle a real time 1/100th second update I will use it for timing if not I will only use it to start the windows timer.

With the way Windows software and PC hardware is set up these days, an input from a PC's serial port would probably be buffered in some fashion, and due to Windows multi-tasking capabilities, quite possibly might not get acted upon for a number of milli-seconds (or seconds on a slow machine ). Therefore, I think the best way to do it would be to keep track of absolute time at the track with a PIC, and send off those elapsed times/lap times/etc to the PC once in awhile...whatever the PIC/PC combo can handle. But again, I wouldn't think it would have to be that fast. After all, wouldn't people be watching the actual race, and not a big ol' TV screen?

[KeithH]

I'm pretty new to this, though I do remember reading somewhere that if you run the Chip at 4Mhz, 9600 baud is just that but if you run the pic at a higher rate, the 9600 baud setting is also multiplied. so you could get the equivelant of 24000baud if you run the chip at 10Mhz?
Sorry if I am wrong.

[skimask]

I'm pretty new to this, though I do remember reading somewhere that if you run the Chip at 4Mhz, 9600 baud is just that but if you run the pic at a higher rate, the 9600 baud setting is also multiplied. so you could get the equivelant of 24000baud if you run the chip at 10Mhz?
Sorry if I am wrong.

You are correct. If you DEFINE OSC 4 for 4Mhz, but actually use 40Mhz, and your serial commands are setup for 9600 baud, you'll actually get 96,000 baud. But running 9600 baud @ 4Mhz, the bit timing is fairly tight and if you're running any kind of interrupts, that'll mess it up.
Better to use DEBUG serial commands @ 4Mhz since they take up less code space.

[Snap]

I finished the project. I ended up using the pic basic pot command to trip a cad to tell the PC a number. I then wrote a VB program with a more accurate Apps call to more or less get a very accurate 1 1000th sec timer. I needed the nice user interface VB provided. I will give out the code for free to anyone who wants it and can learn by it. I am on to my next project now.
Thanks to everyone who helped I hope I can return the favor.
Snap