If you run a recurring video broadcast on Ustream or Google+ Hangouts on Air, or if you have favorites you like to watch fervently, you might enjoy or have practical use for this lighted “On Air” sign. It’s inspired by the studio warning lights used in radio broadcast and TV production, with an internet-connected twist.

Not just for visual flair, these signs also have an important use: they tell others when it’s time to keep quiet, and not to interrupt, barge in the room or hog all the bandwidth watching cat videos.

This “connected” sign is foolproof in a way that a manually-switched sign is not. You won’t leave it on (or off) accidentally. By polling the streaming server(s) directly, the status is always correct with respect to delays, early starts, vacation breaks, etc. The broadcaster and sign can be separated by a wall or by half the planet.

Parts Required

• Raspberry Pi computer (any model) and associated hardware:
• Power supply and USB MicroB cable
• SD card (4GB or larger)
• USB WiFi adapter or Ethernet network connection
• Case
• Keyboard and monitor for setup (can be run “headless” once complete)
• PowerSwitch Tail II appliance controller
• Mains-powered lighted sign
• Jumper extension wires

There are some classy professional studio warning lights available out there, but these do not come cheap — some get into the hundreds of dollars! Really most any lamp or lighted sign will do, or can be adapted if you’re craft-inclined. Our example sign is an inexpensive lighted house number box, a 12V DC adapter and some 2" adhesive vinyl letters from an art store. The more technically-minded might forego the PowerSwitch Tail and assemble something from LPD8806 LED strips, controlled by your own code on the Raspberry Pi.

The PowerSwitch Tail II uses a relay for switching and is therefore compatible with all lighting types — incandescent, LED or fluorescent/CFL.