2 RF transmitters / 1 receiver setup

I'm looking at getting some wireless data sent to the arduino and wondered if someone could recommend some good rf modules? I'm aware of Zigbee, Bluetooth and the more generic RF transmitters but I need 2 transmitters to talk to one arduino - what's the best module for doing this? (BTW, I only need to send a digital 1 on each transmitter as a simple trigger!)



A pair of XBee modules would certainly do that. If you use API mode on the receiving Arduino, the packets will contain the source address. Depending on how complex the logic is behind sending the 0 or 1, you may be able to skip the remote Arduino entirely and just use the built-in digital inputs on the XBee module.

I'm using piezo tranducers to trigger the arduino, so the logic is very simple! I want to take the pulse produced by the piezo and transmit it wirelessly to the arduino which then runs its programme. There are two piezos, so they both need to transmit to the arduino. I won't have a computer hooked up to this, (the arduino is the computer running everything) so can the Xbee's do this?

The short answer is that, yes, the XBee can do that. The documentation's pretty good, and Ladyada has some good tutorials on her site for using the XBee (I highly recommend her breakout board). There are three options that come to mind. One is digital line passing: you'd set up a pin on the XBee to be a digital input, just like on an Arduino. The receiving XBee would then be configured to pass that digital signal out through one of its own pins, and then to the "receiving" Arduino. With this configuration, the Arduino doesn't even need to communicate with the XBee over serial at all. You can do a similar type of line passing with analog signals; the receiving XBee outputs a PWM signal that matches the analog input on the transmitting XBee. Finally, you can have the transmitting XBee sample a digital or analog signal (say, 10 times/second) and then send those samples in a packet to the receiving XBee. This would require processing in the Arduino to pull the sample data out of the packet. The first two options make the XBee pair act like virtual wires. There are timing considerations that need to be addressed, and I don't understand the XBee firmware settings very well, but I think you'll find the Ladyada XBee forum quite helpful (especially if you buy her breakout boards!). :)