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'[EE] Use of Zigbee modules for one way link?'
2010\07\08@161701 by Harold Hallikainen

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I need a one way RF link. I'm considering use of 915MHz, but I can not
find any transmitters with FCC modular transmitter certifications
(http://louise.hallikainen.org/FCC/FccRules/2010/15/212/ ).

Section 3.1 of ww1.microchip.com/downloads/en/DeviceDoc/70329b.pdf
states that the MRF24J40MA has certification as a modular transmitter.

I COULD go Zigbee all the way, except that the "receivers" would generally
need to transmit back to the "transmitter" where the data originates.
Section 3.1.1 of the datasheet requires the antenna be 20cm or more away
from people. This disallows a handheld or portable "receiver."

So, what about the possibility of operating one MRF24J40MA as a
transmitter and multiple MRF24J40MA modules as receivers where the
receivers NEVER transmit? Has anyone tried anything like this? Is it a
good or bad idea?

THANKS!


Harold


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2010\07\08@165234 by Oli Glaser

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--------------------------------------------------
From: "Harold Hallikainen" <spam_OUTharoldTakeThisOuTspamhallikainen.org>
Sent: Thursday, July 08, 2010 9:42 PM
To: "Pic List" <.....piclistKILLspamspam@spam@mit.edu>
Subject: [EE] Use of Zigbee modules for one way link?

{Quote hidden}

Is this any good? It's one of the modules I ordered for the Radio Lights I
mentioned a while back. Cheap, says it's FCC compliant and can be run at
915MHz. What data rate do you need?

http://docs-europe.origin.electrocomponents.com/webdocs/0d71/0900766b80d715d0.pdf




2010\07\08@165403 by Oli Glaser

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Sorry, here's the link to the RS page too:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6728997


2010\07\08@170827 by Harold Hallikainen

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> Sorry, here's the link to the RS page too:
>
> http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6728997
>
>

I believe this module uses the Silicon Labs Si4022 chip. This would be
great if they had an FCC modular transmitter certification. In an email I
got from RF Solutions yesterday, they said:


This unit has not undergone any FCC approvals, though it should be
compliant and therefore should pass tests. As far as I was aware modules
on their own cannot be FCC approved as the function and use of them have
not been specified.


There ARE, of course, FCC modular transmitter certifications (see
http://louise.hallikainen.org/FCC/FccRules/2010/15/212/ ), which the
Microchip Zigbee and various manufacturers' WiFi modules have.

Thanks for the comment, though! Keep them coming!

Harold




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2010\07\08@170959 by Charles Craft

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The trick is that the antenna has to already be integrated into the
module so you get FCC cert without testing?

You were looking for 915Mhz but the Microchip part is 2.4Ghz.
If frequency isn't important can you use something in the 433Mhz range
like a garage door opener without the encoder chip?
Since data is uni-directional how do you account for lost packets?

thanks
chuckc


On 7/8/2010 4:42 PM, Harold Hallikainen wrote:
{Quote hidden}

2010\07\08@171948 by Harold Hallikainen

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> The trick is that the antenna has to already be integrated into the
> module so you get FCC cert without testing?
>
> You were looking for 915Mhz but the Microchip part is 2.4Ghz.
> If frequency isn't important can you use something in the 433Mhz range
> like a garage door opener without the encoder chip?
> Since data is uni-directional how do you account for lost packets?
>
> thanks
> chuckc

That's correct, FCC modular transmitter certification requires an
integrated antenna or approval with a specific antenna. As I recall, you
are allowed to substitute another antenna of the same type with equal or
less gain.

I'm not really concerned about the frequency. The datarate is 10kbps. Data
is transmitted repeatedly with CRC for error detection, so lost or
erroneous packets are ignored. Looking around for FCC certified modular
transmitters, they generally seem to Zigbee or WiFi transceivers. All the
ones I've found also have the requirement that the antenna be 20cm away
from people. A pure receiver would not have this limitation. So, that's
why I'm asking about use of the Microchip Zigbee modules in a one way
transmitter to many receivers configuration.

THANKS for the comments!

Harold



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2010\07\08@173041 by Kevin Jones

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> Looking around for FCC certified modular
> ransmitters, they generally seem to Zigbee or WiFi transceivers.
>All the ones I've found also have the requirement that the antenna
be 20cm away from people.

What about bluetooth ? Lots of wearable devices with bluetooth on board.

Regards,
Kevin Jones

2010\07\08@173313 by Olin Lathrop

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Charles Craft wrote:
> The trick is that the antenna has to already be integrated into the
> module so you get FCC cert without testing?

You can also get modules approved for specific antenna models.  A number of
WiFi modules are available that way with FCC approval.


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2010\07\08@174158 by Richard Seriani

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----- Original Message -----
From: "Harold Hallikainen" <haroldspamKILLspamhallikainen.org>
To: "Pic List" <.....piclistKILLspamspam.....mit.edu>
Sent: Thursday, July 08, 2010 4:42 PM
Subject: [EE] Use of Zigbee modules for one way link?


>
> I need a one way RF
<snip>
{Quote hidden}

Harold,

If I understand what you want to do, I believe it has been done on a small
scale.

Students at Old Dominion University (Norfolk, VA) recently successfully used
the MRF24J40MA in a master-slave configuration. Presently there are 2
independently-addressable slaves, but 3 more are being added for use as
wireless motor controllers.

There is a video posted on the microchip site at:
http://www.microchip.com/mchptube

Good luck with your project.

Richard


2010\07\08@174856 by Vitaliy

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Harold Hallikainen wrote:
{Quote hidden}

Harold, why Zigbee? Why not one of Linx modules -- you don't want to
implement the protocol?

Vitaliy

2010\07\08@180431 by Tech

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----- Original Message -----
From: "Vitaliy" <EraseMEpiclistspam_OUTspamTakeThisOuTmaksimov.org>
To: "Microcontroller discussion list - Public." <piclistspamspam_OUTmit.edu>
Sent: Thursday, July 08, 2010 3:47 PM
Subject: Re: [EE] Use of Zigbee modules for one way link?


{Quote hidden}

Linx has a nice selection of RF modules, and www.rfdigital.com/?targetpage=item&filterpn=RFD21733
has some you might also want to consider.

Regards,

Bruce
@spam@techKILLspamspamrentron.com

2010\07\08@183936 by Sean Breheny

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Could you not turn down the TX power of the module and it would then
be OK to have it closer than 20cm to a person?

As for using Zigbee one-way: Zigbee is a protocol layer on top of the
IEEE 802.15.4 physical/link layer. Most Zigbee modules will work in a
dumbed-down mode where they are only using 802.15.4. In that mode, you
can usually turn retries down to 0 so it won't continue to try to
transmit a packet if it doesn't get a response. Similarly, on the RX
side, you could make some adjustments to prevent transmit (like
setting the channel clear threshold so low that it always thinks the
channel is busy).

Sean


On Thu, Jul 8, 2010 at 4:42 PM, Harold Hallikainen
<KILLspamharoldKILLspamspamhallikainen.org> wrote:
{Quote hidden}

> -

2010\07\08@191524 by Harold Hallikainen

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>
> Linx has a nice selection of RF modules, and
> www.rfdigital.com/?targetpage=item&filterpn=RFD21733
> has some you might also want to consider.
>
> Regards,
>
> Bruce
> RemoveMEtechTakeThisOuTspamrentron.com

Thanks for all the comments thus far! Here are some reply comments:

1. Wi-Fi modules seem to also have the 20cm antenna to person requirement
as a condition of their FCC approval. Their power consumption is also
pretty high.

2. I really only need to get data from here to there over 100 feet or so.
The Si4022 and Si4322 would do great if I didn't have to deal with FCC
certification of the transmitter.

3. The RF Digital transceiver looks interesting, especially if I can set
it up to operate in one direction only. I have to read more about it.

4. The Microchip Zigbee modules are nice FCC certified modular
transmitters, but also contain the 20cm requirement. However, I'm thinking
that if I only transmit one way (it's a broadcast transmission from one
unit to many), the 20cm requirement would not apply on units that are not
transmitting.

I'll look a bit more at RF digital tomorrow.

THANKS!


Harold


3. I don't think any of the Lynx Technologies modules have FCC
certification. Here's a quote from one of their datasheets:

"Linx RF modules are designed as component devices that require external
components to function. The modules are intended to allow for full Part 15
compliance; however, they are not approved by the FCC or any other agency
worldwide. The purchaser understands that approvals may be required prior
to the sale or operation of the device, and agrees to utilize the
component in keeping with all laws governing its use in the country of
operation."




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2010\07\08@195846 by Vitaliy

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Harold Hallikainen wrote:
> "Linx RF modules are designed as component devices that require external
> components to function. The modules are intended to allow for full Part 15
> compliance; however, they are not approved by the FCC or any other agency
> worldwide. The purchaser understands that approvals may be required prior
> to the sale or operation of the device, and agrees to utilize the
> component in keeping with all laws governing its use in the country of
> operation."

Is this a low volume product?

"How much does FCC certification cost?
This depends on how much you have the test lab do. Full transmitter and
receiver testing can cost around $5,000, transmitter only around $3,500, and
the receiver about $1,500. If testing for other countries, such as Industry
Canada or European CE, is desired, then the costs will go up, but will not
generally double. The FCC has authorized the test labs to issue identity
numbers on its behalf so the testing can usually be done in about a week,
depending on the backlog of the test lab. Linx maintains a close working
relationship with Compatible Electronics (http://www.celectronics.com) who extends
excellent service and special pricing to Linx customers."

http://www.linxtechnologies.com/Support/Knowledgebase/FCC/?Article=How+much+does+FCC+certification+cost%3F

2010\07\08@223027 by Harold Hallikainen

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> Is this a low volume product?
>
> "How much does FCC certification cost?
> This depends on how much you have the test lab do. Full transmitter and
> receiver testing can cost around $5,000, transmitter only around $3,500,
> and
> the receiver about $1,500. If testing for other countries, such as
> Industry
> Canada or European CE, is desired, then the costs will go up, but will not
> generally double. The FCC has authorized the test labs to issue identity
> numbers on its behalf so the testing can usually be done in about a week,
> depending on the backlog of the test lab. Linx maintains a close working
> relationship with Compatible Electronics (http://www.celectronics.com) who
> extends
> excellent service and special pricing to Linx customers."
>
> http://www.linxtechnologies.com/Support/Knowledgebase/FCC/?Article=How+much+does+FCC+certification+cost%3F
>

Good information. I thought it would be more than that. That looks
affordable. I'll look at Lynx some more.

THANKS!

Harold




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2010\07\09@044341 by Alan B Pearce

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> All the
> ones I've found also have the requirement that the antenna be 20cm
away
> from people

Ah, so you are re-designing the iPhone 4 then ...... ;))))))))))
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2010\07\09@055917 by Michael Watterson

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 On 09/07/2010 09:37, spamBeGonealan.b.pearcespamBeGonespamstfc.ac.uk wrote:
>> All the
>> ones I've found also have the requirement that the antenna be 20cm
> away
>> from people
> Ah, so you are re-designing the iPhone 4 then ...... ;))))))))))
been fixed already
http://gizmodo.com/5581253/there-fixed

2010\07\09@061709 by Alan B Pearce

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> >> All the
> >> ones I've found also have the requirement that the antenna be 20cm
> > away
> >> from people
> > Ah, so you are re-designing the iPhone 4 then ...... ;))))))))))
>
> been fixed already
> http://gizmodo.com/5581253/there-fixed

<spurts drink over keyboard> <VBG> ...
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