> I'm trying to build a little network of microcontrollers that can 
> report their status to a central server, in a forest. We want to 
> make the various flag/objective stations when we play paintball 
> automatized, and I'm looking for some ideas/recommendations. The uC 
> need to report something simple (eg, which sides owns that station), 
> and maybe a timer. However, it would be great to further expand it 
> to use rfid/bluetooth technology to record when a player is actually 
> 'holding' the station. It would transmit this data to a central 
> server that would display the whole results.

If I were trying to do this on a lowish budget and seeking modest 
range - say hundreds of metres to maybe a kilometre, I'd first look at 
"walkie talkies" IF your regulations allowed their use for this 
purpose. You can source relatively low cost units with requisite range 
and voice operation. Addition of a modest add on aerial will increase 
range (again, if allowed by your regulators). Simple half duplex 
"Aloha net" operation with stations feeding tones to operate the voice 
operated talkies and all listening on the same channel should suffice.

802.11 would be more elegant but also (probably) more expensive, lower 
easy range, harder to talk to.

Bluetooth could be used for external interface with competitors but 
far cheaper would be Infrared using COTS IR 38 kHz modules as are 
used for TV remote reception. Each competitors identifier consists of 
an IR LED or LEDs driven by a very simple processor or even just a 
counter and 38 kHz oscillator. Something like a 4017 with selectable 
strapping would allow each competitor to have their own ID - but a 
small processor would be cheaper and far more powerful.

I've been considering doing something vaguely similar here (where it 
is legal) to send occasional telemetry data bursts using voice 
operated walkie-talkies. Line of sight ranges of several km can be 
obtained with low cost devices.


        RM 

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