Arduino Wireless

I have a project (a tripwire-like system) that I need some very basic Arduino->Arduino wireless communication at up to about 300 feet.

Essentially what I'm doing is wiring up motion sensors that need to say "Yes, I tripped" back to a main control unit.

XBee seems to be overkill (in price and function) for such a purpose because I only need to send a tiny bit of data back (basically the ID of the sensor and that's it).

All I plan on doing is lighting an LED attached to the "controller" showing which sensor tripped.

Any recommendations as to what wireless stuff to look at?

These 315MHz RF modules from SparkFun are cheap ($10 for a pair) and easy to use with the VitrualWire library.

See this message for the code example I have been experimenting with:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1253418574/7#7

Good Luck!

Mitch,

*"HopeRF is a communications library for Arduino that allows multiple Arduinos to communicate using low-cost 'transparent' serial RF data transceivers, such as the HM-TR from HopeRF (http://www.hoperf.com). Detailed API documentation can be found at HopeRF: HopeRF Radio Transceiver Message Library for Arduino"*and in document http://www.open.com.au/mikem/arduino/HopeRF/HopeRF.pdf

These HopeRF units are cheap, and as you'll see ... the code is already there for you to use, at http://www.open.com.au/mikem/arduino/HopeRF/HopeRF-1.1.zip

I doubt you'll be able to find anything cheaper than this:

www.robotshop.ca/on-shine-low-cost-tx-rx-3.html

I doubt you'll be able to find anything cheaper than this:

www.robotshop.ca/on-shine-low-cost-tx-rx-3.html

Data is transmitted via "On-off keyed" (OOK) modulation, which means he'd have to implement a protocol to identify which sensor is transmitting.

HopeRF units are cheap, but not nasty.

HopeRF also make the cheaper RFM12 which is < US$10
You can read about a project using it at http://news.jeelabs.org/docs/rf12.html. There's also an Arduino library provided http://news.jeelabs.org/2009/02/10/rfm12b-library-for-arduino/

OP: I've provided details on 2 transceivers with associated libraries.

This guy made a picaxe based protocol for the units I mentioned:

letsmakerobots.com/node/5194

As you can see it's not exactly rocket science. Several people are using it and it works just fine. And translating it to Arduino shouldn't be a problem either... :slight_smile:

But perhaps the other one is better..I dunno?!

EDIT: Ah...forgot to mention...you could also look into the bluetooth option. It's more expensive but still a lot cheaper than xbee. I believe it's more stable plus you wont have to worry about a receiver setup if your pc is allready bluetooth capable...

Here is a place to start:

www.seeedstudio.com/depot/index.php?main_page=advanced_search_result&search_in_description=1&zenid=b904e9fe3d11fb86c68f2d005cd0c68d&keyword=bluetooth&x=0&y=0

Also, to let you know where you can buy those units... Radio Modules - Main Page

They say the RFM12 will do "300m away in open air" for US$7.90 each (x 2 required)

Or, if you want "Up to 800m" ... the RFM22 is US$12.90 each (x 2 required)

The HM-TR (with TTL interface) is the last item on the page, at US$18.90 each (x 2 required).
(TTL interface - means you can connect this directly to the arduino)

Take note of the supply voltage requirements for each.

Mitch,
I've just had another look at this thread. The products recommended by Ron C appear capable of satisfying your requirements, and are cheaper.

Aniss1001's suggestion could also satisfy your requirements. I found an article on on/off keying (OOK) to help you. It's titled "Wireless Monitoring System" and regards a system very similar to your's.

find at http://www.circuitcellar.com/library/print/0604/RicciBitti-167/RicciBitti-167.pdf

It's amazing what can be done with really affordable RF components nowadays (if you know how).

I hope this information assists you.

Thanks to all that responded.. I just got my 315mhz RF stuff today from Sparkfun :wink:

I'm not sure which method I'm going to use but there is a ton of information here to go through. Thanks again!

I doubt you'll be able to find anything cheaper than this:

www.robotshop.ca/on-shine-low-cost-tx-rx-3.html

Actually, I did. http://www.seeedstudio.com/depot/433mhz-rf-link-kit-p-127.html?zenid=b904e9fe3d11fb86c68f2d005cd0c68d

Cheaper shipping as well.

These small cheap modules work decently well given you do some sort of data encoding/checksum

What's interesting on that seedstudio page is the link to the VirtualWire Arduino library.

This library is cool in the sense that it provides wireless data communications using these cheap modules without using the Serial comms port of the Arduino, thus leaving it free for other usage.

The sent data also includes a "CRC checksum for message integrity".

I just got my 315mhz RF stuff today from Sparkfun

Mitch, report back your experiences/successes :wink:

Getting the hardware to work was definitely the easy part! Coming up with a communications protocol is quite a bit more difficult. Very doable, and I think these are going to work just fine for my purposes (after I create some sort of protocol for them to speak!).

The HopeRF stuff looks great and would be a no-brainer if I had a little more money to spend on the sensors. At almost $20 per transceiver it's significantly more expensive for this project (since the sensors themselves only really need to transmit). I'm going to pick some of those up anyway though. Thanks!

Coming up with a communications protocol is quite a bit more difficult. Very doable, and I think these are going to work just fine for my purposes (after I create some sort of protocol for them to speak!).

I suggest you take a close read of the article I mentioned in my post**"Reply #7 - 27.09.2009 at 12:46:13"**

Here's a link I read up on about using the RF kits, it doesn't use the Arduino environment but the same techniques will work:
http://narobo.com/articles/rfmodules.html

Also, here's the PDF for Virtual Wire, not sure if it was mentioned or not. (I guess it is on the Seeedstudio page, but still:))
www.open.com.au/mikem/arduino/VirtualWire.pdf

I thought after posting yesterday that the VirtualWire library should provide for your implementation protocol needs.

Looking now, I see that Ron C, novice aka moi ;), and CaptainObvious have already suggested this.

Read the pdf doc listed by CaptainObvious.

Additional Info: HopeRF and VirtualWire are separate libraries, and useable as described above. Both written by Mike McCauley.