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After we put the kids to bed last night my wife and I realized we needed to set up some April Fools’ Day pranks. “Quantity over quality!” my wife said, as we began moving furniture into the wrong rooms, putting food dye tablets inside the faucets, and other cheap tricks guaranteed to get a giggle. I decided we needed at least one higher-tech gag. So I built this motion sensing alarm and tucked it into the shampoo bottle recess in the shower. When the kids entered the bathroom they got an earful of beeping piezo buzzer for their troubles!

The basic elements are an Arduino Duemilanove, a PIR sensor, breadboard, ScrewShield, piezo buzzer, LED, battery pack, and jumper wires. When the sensor detects a change in the amount of infrared light it “sees” the alarm sounds. If you’d like more details, stay tuned for my upcoming video on how to build your own.

In the Maker Shed:

mz inthemakershed 5 April Fools' Arduino alarm

arduino duemilanove cropped April Fools' Arduino alarm

Arduino Duemilanove

John Edgar Park

John Edgar Park likes to make things and tell people about it. He works in CG animation at DisneyToon Studios and writes for Make, Boing Boing, and other places online and in print. You can find him at and twitter @johnedgarpark — if you like that sort of thing.

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