Although we’re sure they exist, we wouldn’t want to meet anybody that can’t look back fondly on the halcyon days of youth that included playing hide-and-go-seek. Some kids never grow up and continue the tradition with geocaching or orienteering, but that sense of limitless discovery wanes over time. [Kurt] came up with a small scavenger hunt beacon that brings back the unending wonder that accompanies the unknown.

The beacon is just a simple ATtiny13 that flashes a message with an invisible IR LED. To receive the messages, [Kurt] made a scavenger decoder shield for an Arduino. The decoder includes a phototransistor and a 20×4 LCD display. All [Kurt] needs to do is hold the decoder up to the beacon for the text in the firmware of the ATtiny to be displayed. The beacon is only one inch square and powered by a watch battery, so it can be hidden anywhere.

[Kurt] suggests that the text of one beacon should provide the clue to the next. We’re thinking this is just a great excuse for a walk in the park. You can check out [Kurt]‘s IR decoder getting data from a beacon after the break.

[Eric] sent in this very informative writup on how to use Photo interrupters. These things can be used for many things, he lists pellet dispensing and limit switches. He found one in his junk box and realized he knew very little about it. After some exploring and research, he’s here to educate the rest of us. There’s a good breakdown of the circuit itself which is pretty simple as well as a test circuit and some sample code.