Last month, I built NewsAlarm - a modified smoke alarm wired into the NYTimes NewsWire API. It can be configured to sound in response to any keyword or keywords coming over the wire at a specific frequency; for example, you might set it to alarm when 50% of the headlines coming in contain the words ’space aliens’ or if 10% of the headlines include the word ‘evil robots’. It’s a pretty ridiculous device, meant to embody the equally ridiculous alarmism (pun intended) that permeates mainstream media.
The orginal NewsAlarm was hard-wired to the computer via an Arduino. It worked quite well, but it’s not very convenient – it can only get as far away from the computer as the wires allow, which is only about 5 feet. I wanted the device to be able to be a long way away from the computer processing the NewsWire data, and I also wanted one computer to be able to trigger multiple NewsAlarms. So, I looked into ways that I could connect the devices and the computers wirelessly.
The solution turned out to be the XBee – a cute little device that allows signals to be sent via 802.15.4 wireless. XBees are small, cheap, and can be combined to create simple mesh networks. Perfect! For the wireless NewsAlarm, 2 Xbees act as a transmitter and a receiver. A very simple serial signal is transferred from one XBee to the other when the alarm is triggered. Our system uses two arduinos right now, though it could be re-configured to use one and an FTDI cable.