Everyone loves the dancing monsters that are so popular at halloween, but how do they work?
Inside the dancing monster is an amazing example of elegant engineering that enables everything to be done using a single electric motor and gears. Let's look at a dancing monster that has a button to press in order for it to begin dancing. The button is pressed and a song, usually "Monster Mash" begins to play. A second or two passes, then the motor begins to spin in one direction, and then it changes directions and spins in time with the music. A rubber belt connects the shaft of the motor to a larger wheel. The larger wheel slows the tiny motor down enough to match the timing of the music. The large wheel is connected to another wheel by a metal shaft. The motor spins the belt-driven wheel back and forth and the motion is transferred to the second wheel. A plastic knob fits into a long slot on the inside of the monster's back and works like a cam. Two metal pins attach the monster's back and front body panels to the frame and allow the body panels to move back and forth. The knob will move sideways causing the entire body to move sideways.
The dancing monster's arms each have a vertical plastic tab attached below the elbow joint. The vertical plastic tab has a metal pin connecting it at a slight angle to the side of the body frame at the top of the tab. The tab slides up and down on the pin causing the monster's body to move side to side.
Molded plastic gear teeth fit into similar gears at the top of each leg on the inside bottom of the front and back body panels. A metal pin is in each leg where the leg enters the boot allowing the leg to move from side to side. As the body's side-to-side movement is taking place, the gears cause the legs to move in the opposite direction.
The dancing monster stands on a base that holds the circuit board. This circuit board contains a tiny integrated chip that is the brains of the dancing monster. The chip has the song encoded in it and synchronizes the movement of the motor to the music. This synchronization occurs by alternating the flow of current to the electric motor so that the motor spins in one direction, then reverses, and spins in the other direction.
Four pairs of wires run from the circuit board to all of the other components. The first of these wires are the red wire and the white wire. This pair of wires goes from the circuit board to the battery compartment where four AA batteries are installed. The next pair of wires is the yellow wires. These wires connect the small push button on the top of the base to the circuit board. When the button is pushed, completing a circuit that tells the board to begin the sequence. The third pair of wires is the red and black ones that provide the current to run the motor and the last pair of wires are the white ones that carry a signal to the speakers so the music can be heard.
