Hello mates,

i want to build a system to measure the time of a runner ( in sec. and milisec.) from point A to point B.
My plan is to use 2 infrared transmitters and receivers, connected to a chronometer. When the runner cross point A, the chronometer starts, when the runner crosses the point B, the chronometer stops, and I can get a reading the time in display.
But i dont know how to connect the chronometer and how to start and stop it.I dont know what exactly kind of infrared transmitter and receivers to use too.The max. distance from point A to point B is 100 meters (329 foots)
Can someone to give me ideas or advices.

Thank you very much in an advance!

 

Here's how I did it many years ago (1994) for timing a pinewood derby car. The stopwatch was a very cheap, Walmart-type. The buttons worked by grounding. So, I just hacked it.

All I needed to do was open the case and do some careful soldering.

John

 

Thank you jpanhalt,

Is it possible the start and stop signals to be receive wireless from Infrared transmitter and receiver.I cant understand the whole work of the whole system.If you can explain ..i will be very happy...

thank you in an advance

 

Yes, of course the signals can be wireless. Reynolds (http://www.rentron.com/remote.htm) seems to specialize in hobby applications. There are others, and I am not plugging Reynolds per se. One key thing to incorporate is a code for each command -- like the code on your garage door opener. It avoids false starts and stops from stray signals. The Reynolds products allow you to do that.

John

 

I'm no expert, but having built a little IR remote circuit or two I'd imagine that you'd have trouble reaching 100m in sunlight with an IR signal. Maybe it's because I'm not a good designer (good chance of this), but I've only been able to pull off 10 meters or so, indoors, with my IR circuits.

If I were you, I'd use a break beam IR, but preferably laser, circuit for the start of the timer. I'd get a radio transmitter module that gets activated, through use of a a microcontroller sensing "start beam broken" to modulate the transmitter module on and off which is received by a radio receiver module at the finish line with another microcontroller that starts its internal timer upon reading the start bit from the start line (and increments count files accordingly), and then transmits a byte to a possibly hand held radio receiver/led display that will give you the time.

 

My understanding of the question was that at the starting gate there would be a break beam and at the finish there would also be a break beam to stop the timer. I assumed each TX/RX pair was reasonably close to each other at the timing gates; however, the start and finish gates themselves were 100 meters apart.

I agree, it would be very difficult to have the TX and RX operate on IR and be 100 meters apart. For reasonably short distances though, say up to 8 m, IR should work in daylight. A shielded receiver (like at the bottom of a tube) and modulated beam may be necessary, but those adaptations are commonplace today. The safety trip for my garage door is IR and works reliably at 8 m in bright daylight. In fact, the OP may just want to buy the safety switches for a garage door for his application.

John

 

Plain old Cat5 cable is cheap, use one pair to power the transmitter and one for the receiver return.

 

Thanks for all advices..if everyone know more or have another ideas..u can write it..soon i will try the construct the time system and i will release the results