Hello everyone!
As a newbie with Arduino I want to start mega project - sports timing system for canoe slalom in my country. Canoe slalom is sprint distance - sportist goes through the track on the river. For now we use walkie taklie, one hrono and Excel. Finish line button is controled by human.
The community is small - ~110 participiants (amount of money too). But here comes Arduino...
My goal is to make it automated as possible.
Here is idea easyest part:
"Central brain" - collector of all info and real time "keeper"
"Start/Finisl line" - tho gates with IR/Laser optics switches, arduino Pro mini and Xbee or simple RF transmitter
When sportist break the gates beam, "gates arduino" send trigger to "Central brain arduino" and time start ticking. Same with the finish gates.
But...there could be more than one sportist in the track - every minute one sportist is entering track and sometimes they could change finisfing order.
In standart solutino there could be active RFID tags to identify sportist at the gates (no way of using passive - distance is ~1.5-2.0 m), but that system is too expensive.
Here is ideas second part:
Make "active tag" from arduino Pro mini, RF transmitter + battery + custom waterproof case. Write sketch for arduino to send unique number every ~0.5 second. Sportist befor the race turn "tag" on and when he get to the start gates - receiver on the gates gets unique number fom the tag and lock it with the IR/Laser switch time and send it to the "Central brain".
But what i'm pondering about, isn't a pulse every 0.5 seconds a bit low? Further, the IR/laser, it's not as accurate i'm afraid, especially with boats going up and down and stuff blocking your visual path.
A passive RFID doesn't have to be expensive, not more expansive as your idea at least.
What is the depth of the bow? You could have a long antenna just under the waters surface and detect the RFID's
I don' t know if pulse for 0.5 will be enough - that solud be tested. Actually I woul like to put horizontal laser beam to detect sportist crossing not boat. Start and finish line ar real gates (~1.5m width and 2m high). The track looks like in the pictures in this linkhttp://laseudurgell.worldcup.events.slalom.canoeicf.com/en/whats-canoe-slalom
I think there is no way of putting passive RFID antenna under water - paddlers could damage it and water will totally block signal. Also passive tag distance is in couple cm...
Cheapest arduino pro mini on ebay is $2.08 +transmitter $0.15+cell $0.15 + selfmade case (no ideas for now). I think the price could be lowered if I buy 100 of them.
For all participiants it will be couple of hundreds, but if it will function that way, that would be like active RFID timing for thousand of $.
Have you found your system for canoe slalom yet? We've made a smartphone app, for timing canoeslalom. At the moment we're integrating arduino's to send bluetooth timestamps from the Arduino to the smartphone. (triggered by photobeam) i'd like to share experience.