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PICList Thread
'[PIC]: Wireless networking?'
2005\04\01@000048 by Ale[x] Garbino

picon face
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.

Any ideas for bluetooth/rfid/'presence' signalling?

Even more importantly, should I try to use little rf transmitters, and do it
myself, or woiuld it be better to use 802.11 wireless types? The picotux
(recently posted, http://www.linuxdevices.com/news/NS8386088053.html) looks
great: I could just use tcp/ip for reports and command line scripts, since
they run linux. But they are 100 euros a pop. I'm also concerned about how
much power consumption I should expect from these things, as well as what
range would I get in forests?

Thanks,
Alex


2005\04\01@001526 by Charles Craft

picon face
How big an area do you plan to cover?
Distance between nodes?

Check out the Zigbee stuff on the Microchip site.

{Original Message removed}

2005\04\01@001733 by Bob Axtell

face picon face
Wow, what a GREAT idea!! Best one I have seen here in a LONG time....

You didn't say how MANY you would need. It would be a recharging
nightmare, if wireless too.
Why not go ahead and use ruggedized cat3 with one pair being a comm pair
(RS422) and the other pair GND and PWR? Just bury the cables and be done
with it. Makes the little stations a $25 USD job MAX.

If you provided a running analysis of what happened for the clients to
take home, you'll be a millionaire before you are 40.

Heck, I'll bet I could scrounge up money for this...

--Bob

Ale[x] Garbino wrote:

{Quote hidden}

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2005\04\01@021335 by Russell McMahon

face
flavicon
face
> 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

2005\04\01@023120 by Ale[x] Garbino

picon face
The biggest fields visited are upto 100 acres;
Estimated MAX distance between farthest flags - 1000 yards
Estimated farthest distance from command trailer to nearest flag - 150 yards
These have to be wireless because they are setup for the weekend and then
taken down...
Alex

From: Charles Craft <.....chuckseaKILLspamspam@spam@mindspring.com>
Reply-To: "Microcontroller discussion list - Public."
<piclistspamKILLspammit.edu>
To: "Microcontroller discussion list - Public."
<.....piclistKILLspamspam.....mit.edu>
Subject: Re: [PIC]: Wireless networking?
Date: Fri, 1 Apr 2005 00:15:26 -0500 (EST)

How big an area do you plan to cover?
Distance between nodes?

Check out the Zigbee stuff on the Microchip site.

-----Original Message-----
From: "Ale[x] Garbino" <EraseMEagarbinospam_OUTspamTakeThisOuThotmail.com>
Sent: Apr 1, 2005 12:00 AM
To: piclistspamspam_OUTmit.edu
Subject: [PIC]: Wireless networking?
----------

2005\04\01@032856 by Alan B. Pearce

face picon face
>The biggest fields visited are upto 100 acres;
>Estimated MAX distance between farthest flags - 1000 yards
>Estimated farthest distance from command trailer to nearest flag - 150
yards
>These have to be wireless because they are setup for the weekend and then
>taken down...

fair enough.

>as well as what range would I get in forests?

I think this is going to be the major part of your problem, as power
consumption I do not see as a major problem, because of the way you are
setting things up. It should be possible to set each node up with a sealed
lead acid (maybe a motorbike battery even) as the power source, with enough
capacity to run for the whole weekend without switching off.

The way I would look at doing it is this: -

To get the range you want each node will need an aerial on a pole. It should
be possible to make a suitable demountable pole with a small dipole on the
top that you can point at your master base station. Look in ham magazines
such as QST for examples of how to go about doing this, but I would think
that you could probably make something robust enough out of PVC drain pipe.
With 3 or 4 sections you could probably get above the canopy and have it
shrink to a carryable size, while still being light weight. It won't need to
be tremendously strong as you will have trees that you can tie it to for
bracing.

I was thinking the aerial could be the tin can type that have been used for
wifi stuff, but wonder if wifi is the way to go. Bluetooth into a similar
aerial could also work (see
http://www.tomsnetworking.com/Sections-article106.php for how to detect
bluetooth at a kilometre or more), but I would be tempted to try using one
of the rfID PICs with a suitable aerial, and your own protocol. This would
probably give a lower power consumption as well, possibly also being easier
to interface with. With the PIC at the aerial end of the pole you then use
ordinary cable to get power and data from whatever system you have at the
base of the pole.

then at the base another PIC which does the encoding of whatever data you
want to transmit about who "owns" or "occupies" the site, how many dead,
supplies levels, etc, and send that as serial data up the cable to the
transmitting PIC. A handful of powersupply gubbins with switching regulators
etc, and if you get to the stage of doing extended ones for a week or so,
maybe some solar panel recharge capability, with a panel up the pole in the
sunlight.

Your base then has a similar arrangement on a pole for the aerial, but uses
a less directional one that all the others, as it will need to have a wider
field of view. Then some form of polling protocol which interrogates each
site in turn should serve pretty well. You do not need a high update rate
(somewhere in the 5-15 seconds should be heaps, faster should be readily
achievable) and so I would build in some form of forward error correction to
maximise the data capture if wind blown branches get in the signal path.

Sounds like a real interesting project. Let us know how you get on with it.

2005\04\01@045214 by Bob Axtell

face picon face
Ale[x] Garbino wrote:

> The biggest fields visited are upto 100 acres;
> Estimated MAX distance between farthest flags - 1000 yards

Long but still OK for wired system. Too long for most RF systems.

> Estimated farthest distance from command trailer to nearest flag - 150
> yards
> These have to be wireless because they are setup for the weekend and
> then taken down...

but it can still be wired, just disconnected on weekends. Recharging
would be impractible.

{Quote hidden}

> --

2005\04\01@061715 by Gerhard Fiedler

picon face
Russell McMahon wrote:

> 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.

If you are talking about paintball regulations, maybe taking the speaker
and mike out of the walkie talkies works. Should be done anyway, probably.

Gerhard

2005\04\01@062140 by William Chops Westfield

face picon face
On Apr 1, 2005, at 1:52 AM, Bob Axtell wrote:
>
>> The biggest fields visited are upto 100 acres;
>> Estimated MAX distance between farthest flags - 1000 yards
>>
What's the max distance to the closest neighbor?  There's a bunch
of work being done on ad-hoc message routing in that sort of
situation to solve exactly this sort of issue...

BillW

2005\04\01@092756 by Russell McMahon

face
flavicon
face
>> 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.

> If you are talking about paintball regulations, maybe taking the
> speaker
> and mike out of the walkie talkies works. Should be done anyway,
> probably.

No - I meant that some countries are more restrictive about what you
can use CB bands for - data on CB may or may not be legal. Also adding
extra aerials may or may not be allowed.

Even "as is" 1 km range is doable with good positioning in many
situations with cheap CBs. Just mounting the CB in a container on a
pole would help. I envisaged the use of modern UHF CB's but 27 MHz
units may in fact work better in this application.

It would be quite interesting to make a multihop networked system to
extend range but it hardly seems necessary here. If stations are
either polled by the central station or just transmit pseudo randomly
the low data rate should allow it to work well.

       RM

2005\04\01@111848 by Cris Wilson

flavicon
face
At 11:00 PM 3/31/2005 -0600, you wrote:
>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.
>
>Any ideas for bluetooth/rfid/'presence' signalling?
>
>Even more importantly, should I try to use little rf transmitters, and do
>it myself, or woiuld it be better to use 802.11 wireless types? The
>picotux (recently posted,
>http://www.linuxdevices.com/news/NS8386088053.html) looks great: I could
>just use tcp/ip for reports and command line scripts, since they run
>linux. But they are 100 euros a pop. I'm also concerned about how much
>power consumption I should expect from these things, as well as what range
>would I get in forests?

I faced a similar problem like this last year with some PIR monitors in a
forest.

We first tried using 802.11 and found that if we had a clear line of sight
between the sender and receiver
that it worked fine out to about 200 yards. Of course, we could only get a
clear line of sight with 2 of the
senders. Without a clear line of sight, we could only get about 100 feet of
reception amongst softwood
pines trees, and around 50 feet of reception amongst hardwood hickory trees.

The solution we used was to buy a bunch of the 2-mile range hand held
radios and hack them apart.
We set them all to the same frequency, replaced the send button with a
transistor to act as a switch,
and replaced the microphone with a simple beeping circuit run from a pic.
Once the PIR was activated,
the PIC would broadcast its beeps 5 times.  (The beeps just identified
which monitor it was - 9 beeps
for monitor #9).  On the receiver end, we had another hacked hand held
radio with a PIC that would
count the number of beeps (voltage pulses) that came in and dump it into a
computer serial port. A simple
basic program on the computer then logged the time and receiver number.

I think we pretty much got all of the basic circuits from a model rocket
telemetry web page.

There is one problem with the system though. If two of the monitors
activated at the same time then we
would get the wrong the sensor logged. (If sensor 1 and sensor 2 activated
at the same time, then we
would get 3 beeps and the computer would log sensor 3). Luckily that only
happened a couple of times
and when we looked at the data it was obvious that something had messed up.

Good luck
_____________________________________________________________
Cris Wilson
Information Resource Consultant
College of Architecture, Arts, and Humanities
Clemson University
RemoveMEcrisspamTakeThisOuTclemson.edu
To report problems email: aah_computersEraseMEspam.....clemson.edu




                               

2005\04\01@115220 by Bob Axtell

face picon face
Cris Wilson wrote:

{Quote hidden}

There are two ways of doing this, the RIGHT way and an acceptable way.

The RIGHT way needs the ability to listen for a synchronizing time pulse
to reset the timeclock inside each unit.
Each unit would be assigned a timeslot beforehand, and would only send
during that time period, even if that
delayed the PIR indication for a few seconds. The synch pulse would only
need to be sent once every 6 hrs or
so, and when it occurred also indicated that the sequence is then reset
(the first interval means address 1).
Since you now have given a unit a time slot, ANY pulse during that time
slot will come from that unit. So two
can't send at the same time. To save the battery, I'd turn the RCVR off
except about 5% before its expected
time of occurrence. This is the way the military does security perimeter
sensors.

An ACCEPTABLE way is to make use of the fact that the PIR sensors don't
go off that often. When a signal is
needing to be sent, the unit listens carefully to see if another is
sending. If so, it waits until it is finished PLUS a
random interval , then check again, before sending its own pulse train.
The randomness is needed because if
the interval is fixed, two units listening for an earlier unit to quit
are CERTAIN to write over each other.  It might
be best if the "randomness" is fixed ahead of time.

- - - - -

BTW, Are you aware that an animal can be detected by blocking PIR from
the big bang, rather than straight
IR sensing? Its very good for sensing humans, who can bundle up in coats
so that no PIR gets out, but it
blocks the big-bang energy  well.

--Bob

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2005\04\01@115237 by Mike Hord

picon face
> Any ideas for bluetooth/rfid/'presence' signalling?

I believe the last wireless solutions issue of Circuit Cellar had
an article by a man who place PIR sensors at various areas
about his property and connected them wirelessly back to
home base.  He was able to get remarkable range from cheap
little radio sets (I think) by having a rebroadcast setup, where
messages would get handed off from one station to the next.

A better mousetrap, with a similar node-distributed network...
http://www.circuitcellar.com/library/print/0604/RicciBitti-167/index.htm

AHA!  The article in question was in fact a wireless CAN
network, controlling lamps.  It's in the August 2003 issue of CC,
number 157.  Not online, though.  :-(  I may have it somewhere;
e-mail me if interested and perhaps I can help you out.

Mike H.

2005\04\01@123452 by Cris Wilson

flavicon
face
At 09:52 AM 4/1/2005 -0700, you wrote:
{Quote hidden}

We were trying to detect the times when animals were visiting some natural
art thing that was part of
a student project. The best, easiest, and probably cheapest way would have
been with several
cameras wired to a couple of sensors, but that artistic idiots that I
support didn't want to do that - it
would have been just to easy to borrow some wildlife monitors from the
local game warden. When my
coworker jokingly brought up PIR sensors and wireless all they heard was
the wireless buzzword and
they just had to do it that way.    So with $300 and a week to get it up
and running we ended up doing
that messed up stuff above, they were happy about it and my coworker
learned to never offer another
idiotic solution outside of our office.
Supporting the academic community here often makes me ponder the validity
of my college degrees.


_____________________________________________________________
Cris Wilson
Information Resource Consultant
College of Architecture, Arts, and Humanities
Clemson University
RemoveMEcrisEraseMEspamEraseMEclemson.edu
To report problems email: RemoveMEaah_computersspam_OUTspamKILLspamclemson.edu




                               

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