The folks over at [gTar] decided to create a motion activated talking bacon plush toy to greet visitors to their office.
They started with a toy called My First Bacon, available from ThinkGeek — it’s a plush toy that exclaims “I’m Bacon!” when you squeeze it. But then they cut him open. We can’t imagine what must have been going through this poor self-aware Bacon’s mind!
The hack itself is quite simple. They are basically replacing the “squeeze” circuit with an IR motion sensor — a PIR sensor from SparkFun to be precise. In addition to that they needed a small inverter IC. This is because the standard talking bacon module requires a positive leading edge signal in order to trigger the audio output, and their PIR sensor drives an output pin low — slap on an inverter IC (they had an old schmitt trigger lying around) and you’re ready to go!
In order to reduce the sensing area of the motion sensor they have recessed it slightly inside [Bacon] using a paper towel roll. A carefully placed hole was made in the [Bacon's] tummy, and a familiar white globe sticks out slightly, providing a narrow beam of motion sensing capabilities — just right for catching people coming into the office.