Inside the Fish
The singing fish is actually a very simple robot. It has its own power supply, it senses its environment and acts autonomously on what it senses, it moves in fairly complex patterns (a singing fish is actually more complicated than some of the pick-and-place robots that you find in factories), and it vocalizes -- in other words, it meets all of the qualifications of a robot!

Foam padding is used to flesh out the framework.

In the following pictures, we have removed the latex rubber outer layer to look at the underlying mechanism. What you find is a surprisingly complicated articulated plastic framework driven by three small DC motors:

Plastic skeleton of the fish.

The fish's skeleton has three moving parts:

  • The tail, which flaps back and forth (in the photo above the tail is the black piece on the right)
  • The body, which swings out and away from the plaque
  • The mouth, which moves up and down to simulate singing
Here is a close-up of one of the motors:

This electric motor is used to move the jaws and simulate the singing.

When power is supplied to the motor, the lower jaw opens. As soon as the motor stops, a spring causes the jaw to close. By starting and stopping the motor repeatedly, the jaw opens and shuts, making it appear as if the fish is singing. All three of the motors work in this way -- applying power to them moves the associated body part in one direction, and the spring moves it back.

This electric motor moves the tail section in time to the music. Just like the motor operating the mouth, the tail motor causes the tail fin to move out away from the plaque and a spring makes the tail fin snap back when the motor stops.

This short video shows how the springs snap the parts back into place.