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.
Once we have things cleaned up a bit, we’ll post some schematics and some more detailed instructions on how to get this a system like this working. In the meantime, here are some tutorials that we found useful:
- http://arduinofun.com/blog/2009/03/21/arduino-wireless-xbee-test/
- http://www.ladyada.net/make/xbee/arduino.html
2 Comments
Interesting stuff. Thanks for the links you added too.
The device looks interesting and I have to applaud the innovative way you used a smoke alarm to serve another purpose. However, is setting the alarm for a different function other than to detect smoke and fire somewhat dangerous? Smoke alarms have a very distinct sound and if your neighbors hear it, they may mistakenly think that your house and potentially their place can be in danger. Even burglar alarms systems are equipped with smoke detectors that have a unique sound. These alarms are made for a specific purpose and are integral elements to the response process in emergency situations.