Here at IEEE Spectrum, staffers routinely put Post-It notes on their doors and cubicles to let colleagues know they're out. But you can't slap a note on your door if you decide to work at home at the last minute—which, as I learned this winter, happens quite often when you have a very pregnant wife about to go into labor any instant.
That's why I set out to replace those yellow sheets of self-adhesive stationery with something less, uh, analog—something that would allow me to post the updates electronically. An idea then popped up in my head: Twitter for my door.
It turns out to be a simple DIY project that an experienced hobbyist can complete in a few hours. Or if you're me and this is your first serious hardware project, it might take you a couple of months and nearly drive you insane.
It worked out in the end. Now, when I'm home—or actually anywhere with my phone—I can send a tweet to a small LCD that hangs by my door, thus keeping my coworkers informed of my whereabouts. The LCD also shows current weather conditions in New York City; I thought my colleagues would appreciate this value-added service.
The hardware setup is fairly straightforward. The main component is an Arduino, the popular microcontroller for DIY projects. I used a Duemilanove model (US $30). You'll also need an accessory board called the Ethernet Shield ($45), which allows the Arduino to connect to the Internet. For the LCD, I used a Sparkfun black-on-green 5-volt model with four lines of 20 characters each ($30), which I connected to the Arduino with a thin ribbon wire ($5).
An Ethernet cable plugs into the shield, which attaches directly to the Arduino. Three wires connect the Arduino to the LCD—one for data bits, transmitted serially, the other two for power and ground.
It would have been great to have the device get its Internet access wirelessly, but that would have involved more complicated hardware and frequent battery replacements. So I drilled a small hole in the wall and ran a cable, hoping that the office manager wouldn't notice (or read this article!).