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Author Topic: wireless xbee Ardunio network timing of mountain bike race is this possible?  (Read 3834 times)
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Are the racers racing each other, or the clock?
The clock.

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more than one rider at a time may reach the finish line. Lining to to scan RFID tags to stop the clock hardly seems like a viable solution.
That is a possibility but not that regular an occurrence for it to be a hindrance

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How is sending the switch state going to prove useful? What you need to send is the RFID tag and the time that the switch was triggered
By switch state I just meant that it had been triggered.

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The end time will be defined when the rider scans his/her tag again
That is correct

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Getting them to not pass each other on the course, and to line up neatly at the finish line will be the biggest challenge.
If the system logs the time a tag scans onto the course and then the time it scans off the course then it would not matter if the riders were to pass each other of if a rider failed to ever finish, would it?  Fundamentally it comes down to associating a time stamp with an tag.

Can you tell me if it is possible to connect a real time clock and an Xbee to an Arduino uno at the same time as they would both require the serial connection?

Thanks,

-Jason
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Can you tell me if it is possible to connect a real time clock and an Xbee to an Arduino uno at the same time as they would both require the serial connection?
Sure it is, and no they don't. I'm not aware of any RTC with a serial interface.
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Sure it is, and no they don't. I'm not aware of any RTC with a serial interface.
Ah excellent, I must have crossed my wires somewhere while I have been trying to work all this out.

Aside from the points raised do you see anything else I have overlooked regarding this proposal?  Can you think of a better way to accomplish what I am trying to do?  I know I could use a UHF RFID reader and do away with the photo-switches completely but the cost is prohibitive.

If I have a real time clock module in the start Arduino and a real time clock module in the finish Arduino can I get them to automatically sync time with each other?

Also, am I correct in assuming that the Xbee is transparent to the Arduino so that I can prototype this all on a bench by connecting the boards via a serial cable and not have to cover the additional expense of the Xbee's until the software part is actually finished?

Thanks,

-Jason
« Last Edit: November 06, 2011, 05:47:54 pm by midnite_drive » Logged

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If I have a real time clock module in the start Arduino and a real time clock module in the finish Arduino can I get them to automatically sync time with each other?
No. On the other hand, you don't need to. Scan a tag. Send the data. The receiver time stamps the receipt of the tag, defining the start time. Scan a tag on the other end to record the end time for that tag.
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What constraints are you trying to meet? What sort of distance will there be between the start/end points? How tolerant will you be of false/missing results? Does it need to be tamper-proof? Can you get away with simply banning overtaking? Is there anything stopping you having a human element involved in the normal operation of this?
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No. On the other hand, you don't need to. Scan a tag. Send the data. The receiver time stamps the receipt of the tag, defining the start time. Scan a tag on the other end to record the end time for that tag.
This is how I had originally planned for the system to work but was concerned with latency issues from sending and receiving the data hence the idea to add a real time clock to the transmitter unit.  For simplicity's sake would it be ok to assume that there is negligible delay from when the start gate is triggered and when the receiving Arduino is actually aware that it was triggered?  At the very least would this delay be consistent for every rider throughout the day?

Thanks,

-Jason
« Last Edit: November 07, 2011, 07:22:27 am by midnite_drive » Logged

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For simplicity's sake would it be ok to assume that there is negligible delay from when the start gate is triggered and when the receiving Arduino is actually aware that it was triggered?
Depends on how you actually write the code. The delay can be anywhere from a few hundred nanoseconds to days.

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At the very least would this delay be consistent for every rider throughout the day?
Depends on how you actually write the code. The delay can be small enough to be considered insignificant. If the delay is on the order of microseconds or less, I doubt that the delay will be observable in the measured time with respect to the actual time. Certainly the displayed value of the measured time could have more variation (between the measured time and the displayed time) than the actual delay values.
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What constraints are you trying to meet?
I would like to be able to identify when a rider enters and leaves the course so that I know how long they are on course for.  Each rider needs their own unique identity.  Start and finish are significantly far apart to need some form of wireless communication.  Will need to handle multiple riders on course at one time.

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What sort of distance will there be between the start/end points?
I was considering an Xbee pro for the transmitter that has a theoretical outdoor line-of-sight range of a mile.  These races take place on hillsides and often in quite dense woodland but the start is always at a much higher vertical elevation than the finish.

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How tolerant will you be of false/missing results?
This is not for any regulatory body but I would rather avoid any if possible.

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Does it need to be tamper-proof?
Not really, this is just for use between friends and clubs so I wouldn't expect any attempts to cheat or manipulate the system

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Can you get away with simply banning overtaking?
No, but we could theoretically only allow one rider on course at any time.  However this is not desirable as on a longer course (3 min for a fast rider or 5+ min for a slow rider) with many people each requiring 2 runs, you can quickly run out of time.

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Is there anything stopping you having a human element involved in the normal operation of this?
It needs to be as automated as possible, I don't want someone writing down riders numbers as they finish for example.

Thanks,

-Jason
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Depends on how you actually write the code. The delay can be anywhere from a few hundred nanoseconds to days.

The delay can be small enough to be considered insignificant. If the delay is on the order of microseconds or less, I doubt that the delay will be observable in the measured time with respect to the actual time. Certainly the displayed value of the measured time could have more variation (between the measured time and the displayed time) than the actual delay values.

Thank you for confirming that for me, will hopefully make the project a little simpler to program and also cheaper.

Knowing what you do about the project, do you think at an Arduino FIO would be suitable to use for the start transmitter?  Am I correct in assuming that I can connect the ID-12 and a photoswitch without issue or would it be more straightforward just to use an Uno board instead?

Thanks,

-Jason
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