Cheap wireless arduino temp. gathering network

Hello, I am documenting on making a temperature data logging system for my holiday house. I am searching for a way to get multiple arduino-s to send data to a central one wireless. I have thought about XBee but the price is quite high for the whole system, it will have around 15-20 temperature gathering arduinos each with one temperature sensor that will send data to the master one every 5-10 minutes. Ho you have any idea on this ?

Best regards, Mike S.

Look at JeeLabs' JeeNodes: http://news.jeelabs.org/ Also for sale at moderndevice: http://www.moderndevice.com/products/jeenode-kit

have you had any experience with these "jeenodes" in wireless networking ?

SparkFun's RF transmitters and RF receivers + standalone Arduinos and temperature equiptment. Just make sure only one transmits its info at a time, or you will have trouble. At that price, you might even consider getting a receiver for every transmitter and a transmitter for the receiver too, so each knows when to send its data.

On the transmitter page it says:

Only one 315MHz transmitter will work within the same location.

But that's not true, so long as you send the data with checksums, and only transmit one arduino at a time.

is there any kind of library made for this ? I think it would take me some time to make the transfer protocol to work. Checking that no other unit is transmitting. Then send the data with checksum and stuff. and them read the data from the main unit, also with data sync... that would take some tinkering...

is there any kind of library made for this ? I think it would take me some time to make the transfer protocol to work. Checking that no other unit is transmitting. Then send the data with checksum and stuff. and them read the data from the main unit, also with data sync... that would take some tinkering...

Here's a tutorial.

It's definitely been done many times.

so going with virtualWire and a dozen of Arduinos i assume. that would seem too easy :))

No experience with JeeNode, but I read the blog almost daily, and I can tell you it is one of the most thorough I’ve seen. Documentation and support seem to be plenty and JCW (the author) seems to be a fine gentleman.

I have a network of jeenodes with DS18B20 temperature sensors and some SHT11 sensors throughout the house. It works reliably - and even better the nodes run off AA batteries.

I can recommend this - at a much lower price than the Arduinos, and much easier to install.

A set of simple and good Arduino libraries are supplied for the Jeenodes, making programming very easy for anyone used to Arduinos.

As a matter of fact I have both Ardunios and jeenodes on my network.

Depending on how much of the software you do yourself, vs using stuff from libraries, you may need to read up on...

http://en.wikipedia.org/wiki/Carrier_sense_multiple_access_with_collision_detection

Basically: You need to arrange to avoid (hard) or deal with (less hard) the situation of two of the remote sensor stations "talking" at the same time to the main "collect the data" station.

=== You can infer a lot of what you need to understand from....

http://talk.jeelabs.net/topic/25

=== If you are not going the JeeNode route, have a look at virtualWire...

www.open.com.au/mikem/arduino/VirtualWire.pdf

... which, to quote from that....

VirtualWire is a communications library for Arduino that allows multiple Arduinos to communicate using low-cost RF transmitters and receivers.

=== Note that the nice people who make all the laws to keep us confused and big commerce safe are relevant here: There are RF products for at least two frequency bands, and where you are determines which you may legally use... and illegal use really could matter, despite my cynicism about lawmakers. The JeeNode and....

http://www.moderndevice.com/products/jeenode-kit

... sites have info, sort of, on those issues. (There's a link to the JeeNode site from ModernDevice's)