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'[PICLIST] [EE] Wireless links & PICs'
2002\04\15@180522 by mluvara

picon face
Anyone had experience with wireless data transmission interfaced with PICs?

I'm building a telemetry system and have run into
problems finding a suitable wireless transceiver or rx/tx combo. Looks like it will have to be 900MHz unlicensed (saw something in FCC pt 47 that talks about temp, pressure, etc and that it cannot be transmitted in the 433MHz rance) and I
would like it to be smaller than about 2"x3"x1.5" if possible. Range of 1000 ft would be good.

Anyone have some sources or experience in this
area? I've looked at a lot, but maybe not all

Regards,
Michael

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2002\04\15@182723 by Sean H. Breheny

face picon face
Hi Michael,

Check out:

http://www.rocket-roar.com/BWCM/900MHz/over.html

or

http://www.rocket-roar.com/BWCM/900MHz/hard.html

if you want to skip ahead to the hardware.

This is part of my wireless tutorial site that I am still not finished
with, but this section (probably the most important part) which takes you
through the design process of making an error detecting/ARQ error
correcting communication system between two PICs.

I hope to start selling PCB blanks for this yet, but the current problem is
that the boards can be made smaller and I want to do that before going into
production. For now, you can get the schematic, code, and board layout from
that site.

Sean

At 02:54 PM 4/15/02 -0700, Michael Luvara wrote:
{Quote hidden}

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2002\04\15@183753 by mluvara

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John,
Sorry for not making it clearer, but this is a line of sight use. It is an outdoor system, specifically for a model aircraft where virtually no obstructions are.

I would have preferred the 260-470 MHz band for less directivity, but the transmit power has to be halved and the transmission period is greatly reduced in order to use that band.

Regards,
Michael


On Mon, 15 Apr 2002 15:23:06 -0700 John Dammeyer <.....johndKILLspamspam.....autoartisans.com> wrote:

Hi Michael,

1000 feet is pretty far if you are trying to meet FCC regulations.  Is
your target point to point with just two nodes or are you looking for a
multi-master system or master/slaves?  Antenna selection is also very
critical here.  At 900MHz you are really line of sight and even simple
objects in the way can cause problems.

Regards,

John Dammeyer
Automation Artisans Inc.

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2002\04\15@184212 by John Dammeyer

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face
Hi Sean,

Very impressive site!

John Dammeyer

Automation Artisans Inc.
2335 Tanner Road
Victoria, BC
CANADA V8Z 5P8
Ph. 1 250 544 4950
Fx. 1-250-544-4954

> {Original Message removed}

2002\04\15@192543 by mluvara

picon face
Sean,
Thank you for the info. This is interesting as I have seen the Linx modules and thought about implementing it this way if I cannot find an off the shelf unit.

One question - what range have you been able to get out of it in an outdoor environment?

Thanks,
Michael


On Mon, 15 Apr 2002 18:25:54 -0400 "Sean H. Breheny" <shb7spamspam_OUTCORNELL.EDU> wrote:

Hi Michael,

Check out:

http://www.rocket-roar.com/BWCM/900MHz/over.html

or

http://www.rocket-roar.com/BWCM/900MHz/hard.html

if you want to skip ahead to the hardware.

This is part of my wireless tutorial site that I am still not finished
with, but this section (probably the most important part) which takes you
through the design process of making an error detecting/ARQ error
correcting communication system between two PICs.

I hope to start selling PCB blanks for this yet, but the current problem is
that the boards can be made smaller and I want to do that before going into
production. For now, you can get the schematic, code, and board layout from
that site.

Sean

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2002\04\15@214902 by Sean H. Breheny

face picon face
Thanks! I hope it will be even more impressive when I *finally* get it done
(if you look at the table of contents you will see how much is not yet
finished, although a lot of it has been written up but not converted to
HTML with illustrations, etc.)

Sean

At 03:43 PM 4/15/02 -0700, you wrote:
{Quote hidden}

> > {Original Message removed}

2002\04\15@215736 by Sean H. Breheny

face picon face
Hi Michael,

You are welcome! What do you mean by "off-the-shelf unit"? I would consider
the Linx modules to be off-the-shelf, unless you are talking about ones
which include a microcontroller to do the error correction in the unit. If
that's what you want, you might look at ones from Radiometrix
http://www.radiometrix.co.uk/

Unfortunately, I have not yet tested these in an outdoor environment. I
just got them finished right before I had to go back up to school and have
not had the time to do an outdoor test. Another complicating factor is that
they need a PC in order to view the output, so I would have to use a
laptop. I do have one, but it is ancient and the battery is gone, so I can
only use it with a power supply :-)

Sean

At 03:47 PM 4/15/02 -0700, you wrote:
{Quote hidden}

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2002\04\15@233705 by mluvara

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Hi Sean,
What I meant by "off the shelf" was that there are some rs-232 interfaced
or similar units that, like you said, have some sort of microcontroller in
to do the error correction. I've found a few. They price at about $100-$200
+ ea, so that brings me to about $200-400 + for a complete unit in very low
volumes. I really wouldn't mind spending that much for a unit if I knew it
delivered substantial range. However, if I ever decide to sell a unit like
this, I would like to keep the cost down.

Abacom Technologies has some devices which are "off the shelf"
http://www.abacom-tech.com/transceivers.htm
or
Maxstream has some awesome radio modules... Unfortunately, a little pricey
at $400 for a pair with a development package.
http://www.maxstream.net/products_wirelessoem.html

The limiting factor with the Radiometrix modules is that they don't give
the range that I want and it seems that all of the 433MHz modules get
better power outputs and range, of which I can't use because of FCC part 15
regulations. But, then again, the rules also say that if I build less than
five for personal use, I can forgo the FCC regs...

The main problem is that I keep finding loads of 433MHz modules... Need to
find more 900 MHz!

BTW Sean - saw that you are into R/C models. That's what I'm developing
telemetry for - http://www.LuvaraAirRacing.com

Regards,
Michael



> [Original Message]
> From: Sean H. Breheny <RemoveMEshb7TakeThisOuTspamCORNELL.EDU>
> To: <spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU>
> Date: 4/15/02 6:55:48 PM
> Subject: Re: [EE] Wireless links & PICs
>
> Hi Michael,
>
> You are welcome! What do you mean by "off-the-shelf unit"? I would
consider
> the Linx modules to be off-the-shelf, unless you are talking about ones
> which include a microcontroller to do the error correction in the unit. If
> that's what you want, you might look at ones from Radiometrix
> http://www.radiometrix.co.uk/
>
> Unfortunately, I have not yet tested these in an outdoor environment. I
> just got them finished right before I had to go back up to school and have
> not had the time to do an outdoor test. Another complicating factor is
that
> they need a PC in order to view the output, so I would have to use a
> laptop. I do have one, but it is ancient and the battery is gone, so I can
> only use it with a power supply :-)
>
> Sean
>
> At 03:47 PM 4/15/02 -0700, you wrote:
> >Sean,
> >Thank you for the info. This is interesting as I have seen the Linx
> >modules and thought about implementing it this way if I cannot find an
off
{Quote hidden}

- Michael Luvara

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2002\04\16@095007 by Micro Eng

picon face
The original poster mentioned something about FCC regs that prohibited temp,
etc data to be sent in the 400MHz band.  Is that true? Andrew?



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2002\04\16@114706 by Paul Hutchinson

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face
The FCC rules don't prohibit sending data at 400MHz but, they do limit you
to sending data only once every 10 seconds and with a transmission duration
of less than 1 second, IIRC.

Paul

> {Original Message removed}

2002\04\16@115330 by John Dammeyer

flavicon
face
Hi,

What that mens is that if you use the 400MHz band the onboard aircraft
uC would have to log 10 seconds worth of data, compress it, and send it
out in less than one second while accumulating the next 10 seconds
worth.  It all depends on how much data is desired and how easily it can
be compressed.

John Dammeyer

> {Original Message removed}

2002\04\16@122350 by Sean H. Breheny

face picon face
Actually, I do think that they prohibit you sending "real" data such as
temperature, humidity, or any measurement of a real quantity on that band.
I know that sounds really weird, but I saw it written up in an app note on
the FCC regs by (IIRC) Linx Technologies. Check out their site.

Sean

At 11:44 AM 4/16/02 -0400, you wrote:
>The FCC rules don't prohibit sending data at 400MHz but, they do limit you
>to sending data only once every 10 seconds and with a transmission duration
>of less than 1 second, IIRC.
>
>Paul
>
> > {Original Message removed}

2002\04\16@123316 by mluvara

picon face
I should have been clearer. FCC part 15.231 has a few subsections that
describe the use of the band. It basically says that no "real" data can be
transmitted. This band is for transmissions that are not truly periodic.
under 15.231 paragraph a. "Continuous transmissions, such as voice or
video, and data transmissions are not permitted". From what I read, they
want this band to be a "control" use - garage door openers, remote
switches, etc and not transimitting data. You can transmit data under
paragraph e, if you cut the output power in half and make it 10 sec between
transmission.

Like Sean said, Linx technologies has a nice app note that has this
summarized and with the FCC rules attached.

Michael


> [Original Message]
> From: John Dammeyer <EraseMEjohndspamAUTOARTISANS.COM>
> To: <RemoveMEPICLISTEraseMEspamEraseMEMITVMA.MIT.EDU>
> Date: 4/16/02 8:55:06 AM
{Quote hidden}

> > {Original Message removed}

2002\04\16@181416 by Harold M Hallikainen
picon face
On Tue, 16 Apr 2002 09:33:33 -0700 Michael Luvara <RemoveMEmluvaraspam_OUTspamKILLspamEARTHLINK.NET>
writes:
> I should have been clearer. FCC part 15.231 has a few subsections
> that
> describe the use of the band. It basically says that no "real" data
> can be
> transmitted. This band is for transmissions that are not truly
> periodic.
> under 15.231 paragraph a. "Continuous transmissions, such as voice
> or
> video, and data transmissions are not permitted". From what I read,
> they
> want this band to be a "control" use - garage door openers, remote
> switches, etc and not transimitting data. You can transmit data
> under
> paragraph e, if you cut the output power in half and make it 10 sec
> between
> transmission.
>
> Like Sean said, Linx technologies has a nice app note that has this
> summarized and with the FCC rules attached.

The cited section is also available at
http://www.hallikainen.org/cgi-bin/section.pl?section=15.231

Harold


FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com


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