When we got TJ he was able to play his cartridges and move according to his original programming. But we wanted to help him move on his own. Normally we'd title this section "Controlling TJ," but interestingly that language doesn't seem appropriate for such a friendly bear. Empathy for the machine is much easier to achieve when the machine is fuzzy. Here's a full list of what TJ can do. He can execute seven independent types of movement. Those are: 

•  Wiggle both of his ears. 
• Open and close both eyes. 
• Open and close his mouth.  
• Rotate his head left and right. 
• Tilt his head up and down. 
• Raise and lower his left arm. 
• Raise and lower his right arm. 

Incredibly, TJ accomplishes all this using just three small DC motors.

Identifying the motors

The ears, eyes and mouth are all controlled by a single DC motor located in the gearbox that occupies most of TJ's head. We'll call this Motor 1. His other two motors are located in his body, and control his neck and arm movement. When Motor 1 is run in the forward direction, TJ cycles through ear wiggles and eye blinks. When the motor is run backwards, TJ opens his mouth. Turning the motor forward again will first close the mouth, then resume the ear wiggle and eye blink cycle. 

As a result, TJ can only do one of his facial animations at a time. If he is talking, he cannot also blink or ear wiggle at the same time. Additionally, since the eye blink and ear wiggle cycles are linked and only move in one direction, TJ must wiggle his ears once between every eye blink. 

The head motor can change directions at any time, which means that TJ can open and close his mouth at any point in the eye/ear cycle, just not simultaneously. For example, to have TJ talk while his eyes are closed, the operator can run the head motor forward though the ear and eye mechanics until the eyes are closed, then cycle the motor backwards and forward briefly to open and shut the mouth. The eyes will stay closed. Once the motor is run forward enough to completely close the mouth, the eye/ear cycle will continue, and the eyes will open again. 

The rest of TJ’s motion is accomplished by the two motors in his body. As with the head, the motors are geared to perform one action when running forwards and a different action when running backwards. Motor 2 is responsible for raising and lowering TJ’s left arm when running in the forward direction, and also nodding his head up and down when running in the backwards direction. Similarly, motor 3 is responsible for the movement of the right arm and also the head turning right and left. 

Like the eyes and ears mechanism, the head and arm movements are also cyclical and unidirectional. This means that TJ can, for example, lift his arm and stop in an arbitrary position, but he cannot put his arm back down again until it has first been raised all the way to the top, at which point it will continue its cycle down again. The same is true for head turning and nodding.