Best cheap wireless communication?

Device x has a button and is 25 feet from device Y. Device Y needs to know when the button is pressed and activate device Z, but it has to be cheap and if I have a lot (A LOT) of these sets near eachother they still need to work without interfering with eachother. Best Solution?

Comments

[frollard]

How much power can it consume?
how physically robust must it be?
how much bandwidth? (how often are you turning one/some/many/all of them on or off)?

There are radios like the xbee with short-range mesh networking to microcontrollers; each being assigned an address and any node capable of sending or receiving. They aren't the cheapest but they are inexpensive in quantity/lower end models with lower power. *(under $10 each in quantity according to a forum post I found)

[bwrussell]

Depending on what you're connecting these to and what cheap means to you, a radio mesh network will get the signals where they need to go.

[frollard]

the question that really answers this question...

WHAT exactly are we making, in what environment, and what design constraints apply? :)

This could be anything from laser-tag to mesh robots.

[snowpenguin]

Truth is I don't know what we're making, it's a research challenge that was issued to me by a mentor.

Cheap means cheap, as in Xbee is certainly too expensive. IR is of course going to be the cheapest solution, but I don't know if line of sight is something that this system would have.

[frollard]

...remembering IR is virtually useless outdoor/in sunlight...

It's unfortunate because a mesh network of even the cheapest wireless I can think of is at least $10/node...

[kelseymh]

I wouldn't use individual wireless transmission with "A LOT" of devices, when the range is that short. You'll run out of bandwidth in the FCC-allowed frequency ranges, if you space them far enough apart to avoid interference.

You could pull twisted pair (or even just a single wire) for each X-Y pair, but that gets unpleasant (bulky cable or really wide ribbon) with "A LOT" of devices. You could pull optical fiber and put a multiplex/demultiplex transceiver at each end (like HP's GLink), but that is quite pricey.

What about a single frequency receiver with a multipin output (you can get 50-, 100- even 200+ pin connectors), with software to decode a transmitted address and put a signal onto the correct pin? Your transmitters would send their address digitally to the receiver, all on the same frequency.

[snowpenguin]

It MUST be wireless, and each set of devices is not going to be necessarily connected with the others so one giant radio communication line is out of the question sadly. I was thinking IR might work, but I want to see what else I can figure out first.

[mpilchfamily]

IR will probably be your best bet so long as you have line of site between transmitter and receiver. Then each device can be looking for a specific code. You could have a single transmitter with multiple buttons and cover multiple devices.