Toy Ingenuity

I like the little gems of ingenuity and economy of design found inside crappy toys. I was taking apart some electronic toys yesterday, as is my wont. This particular toy had a few neat mechanisms, but I thought this use of rotary encoders and cams was especially cool.

The toy has these two cylinders that the kid rotates. One cylinder has four torsos – a clown, a girl, a lion, and something else. Another cylinder has their corresponding lower-halves. When you turn them and match up the correct body, you get some beeps, blips and flashes. In the photo is the simple mechanism that tells the microprocessor what the position of a cylinder is. My photo only shows the parts that make up the torso cylinder, so there’s another setup like this for the legs cylinder.

Rotary encoder from a crappy electronic toy

In case you can’t figure it out from the photo, here’s what’s happening: That little metal comb touches a piece of the inner circle to a piece of the outer circle. It only does this at certain times though. See, there is a kind of cam and follower ring (the four big teeth-bumps) around the outside of each part. The follower is the part with the comb and there are springs under there to make sure that it actually follows the bumps (cams) on the other side.

That inner part of the drum (with the comb) goes up and down as it follows the cams on the other part. When you’re looking at a complete torso or leg-set, it’s in the down position – and the comb is making a contact. When it’s between figures, it’s in the up position – and the comb is floating above the metal contacts. The comb only touches contacts when the inner part of the drum is down. Coincidentally, the only time this happens is when you’re looking at a complete picture on the drum – not when you’re between pictures. Simple but smart.