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Topic: Need help in selecting XBEE 868 Mhz part (Read 2 times) previous topic - next topic

eagleeye

Dec 31, 2012, 12:56 pm Last Edit: Dec 31, 2012, 02:20 pm by eagleeye Reason: 1
Hi
I need help in  choosing an XBEE 868 MHZ part so that I can
solve the following problem. I am new to XBEE..

I have a small farming prototype which I am going to choose
the arduino FIO.

I chose 868 mhz for long range and low transmit power.
my data can be as slow as 1200 baud.

1. I would have 20 Arduino fios with some soil and temperature sensors
and light level sensors.


3.0 I would like to try to change batteries every 2 months or longer if possible.

3.1 I would be using alkaline batteries
(FIO is limited to 3.3 volt but the FTDI cable is actually providing 5 Volts so 3 D sized
alkaline batteries providing 4.5 volts when new should work? or should it be 4 D
sized providing 6 volts when new?)

4. The Ardunino Fios will be in sleep mode and wake up and transmit their data and go into  sleep mode
every 30 minutes.

4.1 transmission would be turned off when no light is detected using a LDR (nighttime)
if growing lights are turned on, the transmission will start again since I am also
measuring light levels.

5. The main receiver would have a very large battery or is AC powered, like
a LAPTOP.

I understand XBEE 868 digimesh is a restricted export controlled product.
so I would like to avoid that as much as possible.

I am counting on the long range of the 868 mhz to avoid having to buy
digimesh based products that can self repeat infomation.

My terrian would have some small undulations on it as it is a farm
in a hilly area. Range would be about 1 kilometer square.

Which XBEE 868 model can I choose to make this successful?


Allan




Boffin1

A cheaper option would be the RFM22B  which I am presently experimenting with, it can also be set up as a mesh arrangement, but it has evidently   about a kilometer range anyway ( I havnt tested the range yet )

There is a library RF22 for it, with examples if simple one way transmission ( which I have working )   to a mesh network.

The Arduino should handle you power requirement with sleep mode, some of the experienced guys on this forum have got the quiescent current down to a  handful of microamps in sleep mode ( which will give you a life probably limited to the batteries shelf life ! )
With my mobile phone I can call people and talk to them -  how smart can you get ?

eagleeye

Hi
Yeah the 433 mhz is a good option.. you mean it has automatic repeater
function built in? This means I can simply power up some rfm22s and leave
them repeat signals around blind spots? Thanks for the tip, I will study it
carefully.

I stil would like to hear what the Xbee Gurus say about my requirements.

I went to the WASPMOTE product web page. Seems they
have an impressive range of 'plug and play' solutions. however
its very pricey and my farmer has an end of life for this project
of 2 years.

http://www.libelium.com/products/waspmote/hardware


Regds
Allan



PaulS

Quote
I stil would like to hear what the Xbee Gurus say about my requirements.

More than half of your requirements have nothing to do with the kind of radio you choose. Sleeping an XBee is possible. Waking up the Arduino because the sleeping XBee received a broadcast won't happen, because sleeping XBees don't receive broadcasts.

Measuring light level is not something that the XBee is going to do. The Arduino is, but not while it is sleeping.

Quote
2. From a PC or other embeded board I would like to transmit a command to
all the 20 Arduino fios and get them to respond with the data.

4. The Ardunino Fios will be in sleep mode and wake up and transmit their data and go into  sleep mode
every 30 minutes.

You say that the data needs to be broadcast in response to the request for data. The Arduino and XBee have to be awake to receive that broadcast.

Before choosing hardware and sleep modes, you need to get your requirements straight.

eagleeye



Quote

2. From a PC or other embeded board I would like to transmit a command to
all the 20 Arduino fios and get them to respond with the data.

4. The Ardunino Fios will be in sleep mode and wake up and transmit their data and go into  sleep mode
every 30 minutes.
You say that the data needs to be broadcast in response to the request for data. The Arduino and XBee have to be awake to receive that broadcast.

Before choosing hardware and sleep modes, you need to get your requirements straight.

Hi, I forgot to remove point #2. as I was typing the message.

My idea is this..

A. FIO should wake up every 30 minutes ( the XBEE should stay sleeping)
B. FIO checks for light, no light? goes back to sleep , if light detected FIO wakes up the XBEE and transmits
    puts the Xbee to sleep and goes into sleep mode.


Allan















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