Xbee interfearance

[Schnabel]

Hello All,
I am working on an individual project and a question popped into my head. Should said project appear at an FRC event and it was using the xbee pro 900 to communicate with its controller, what kind a havoc could be caused to the wifi radios on the robots? The thing I was looking at was that the xbee operates on the 900mHz band while the wifi radios operate on the 2.4 and 5 gHz bands. Would the robots be immune to the xbee, or would there be a potential for interference? I'm simply a computer programmer, so I don't know much about this type of stuff.
Thanks to any responses!
Schnabel

[DonRotolo]

You'd have to wait for the 2011 rules I suppose, but in 2009 we used a 900 MHz communication link from stands to pit for scouting data transfer, all FIRST legal. So on the surface, 900 MHz might be OK in 2011.

[EricVanWyk]

Check the 2011 rules when they are available, but you should generally be good to go.

In general, if the frequencies are different, there shouldn't be interference. In practice, this is only true if both devices were designed and built properly. For example, I saw some cheap 2.4GHz devices die in the presence of 5GHz interference. Turns out, someone had swapped out the main filter for something cheaper and completely ineffective.

[tonystark_23]

Hmmm...I wonder if you are planning a hover bot "scout" to fly above the competition in the pits??

[Al Skierkiewicz]

In the past rules only allowed certain devices pre approved by FIRST Engineering to be used on the robot.

2010
<R58> No other form of wireless communications shall be used to communicate to, from or within the ROBOT (e.g. radio modems from previous FIRST competitions and Bluetooth devices are not permitted on the ROBOT during competition).
<R86> Other than the system provided by the ARENA, no other form of wireless communications shall be used to communicate to, from or within the OPERATOR CONSOLE (e.g. active wireless network cards and Bluetooth devices are not permitted in the OPERATOR CONSOLE).
Wireless cameras have also been included in this language.
I would not think that engineering would allow a change in this language. Check the 2011 manual and/or the Q&A when they become available.

[EricH]

Al, AFAIK this is not an FRC robot, being an individual project with a wildly different controller. Therefore, the FRC robot rules do not apply.

The standard "no wireless communications (other than cell phones)" from Section 3 would still apply, however.

If I were you, Schnabel, I'd contact FRC Engineering beforehand and get a pre-clearance (i.e., we don't think there will be a problem), then clear it at the event with on-site staff.

[Al Skierkiewicz]

Erik,
I posted a few of the rules because of the statement that he intended this to be used at a First event. To follow up, interference can come from the mixture of a variety of signals. Most often these are on frequency or harmonics (sub harmonics too) and in general the second and third harmonics are the most incipient. However, anything that can mix with 900 MHz and harmonics can produce a signal on 2.4GHz known as intermod distortion. Second harmonic mixing with a 450 Mhz business band/police radio might produce a signal that swamps communication at 2.4GHz

[EricH]

Yep, which is exactly why I noted that Section 3 was the applicable section (wireless communications in general are disallowed, with the exception of cell phones and official FIRST business) and recommended that he check with FRC Engineering before and at the event, to see if there were any known issues in general and/or at the venue.

[Schnabel]

Thankyou all for your responses! I agree that I will first look into the rules when they are available, I will then talk with FIRST engineering. I feel my idea will help a lot of people, but I don't want it to come at the cost of hurting the competition.