I'm going a bit crazy trying to work out how a marketing gizmo operates. Would appreciate any thoughts!
My local supermarket just installed a small Pillsbury promotional freezer, roughly cube shaped, and about four feet on each side. On the side it has the doughboy, and a word bubble that says "Hear me giggle!". I naturally assumed there would be a microswitch on the lid triggering a speech module, or maybe a light-gate triggering when you reach in.
However, it's much, MUCH more subtle than that. If you open the lid, nothing happens. The thing only giggles when you touch a product inside the freezer. However, not ALL products trigger it. The freezer contains mostly cinnamon buns and biscuits, which come in a foil-coated cardboard tube with steel ends. If you touch one of the metal ends, the giggle starts. If you touch the tube part, it might or might not start giggling, depending on whether you touch a shiny part or a printed part.
There happened to be a non-metallized cardboard box of frozen pastry in the freezer also; handling that box, picking it up, moving it about, etc. did not trigger the voice.
The inside of the freezer is all plastic, so I don't think it operates by making the contents one plate of a capacitor. My best guess is some kind of microwave motion/prox sensor, but I'm damned if I can work out the details.