In my free time, I have been converting a plush Mickey Mouse to an interactive toy. The figure is able to sense motion, detect temperature change in its hand, and respond to a button press. Its reactions include playing an audio file specific to the type of input and movement in three degrees of freedom (its spine and both shoulder). I undertook this project because I am interested in animatronics and their ability to interact with people.
Currently, the hardware portion is complete. I am still writing the software (in C/C++) that will control the motion, but it currently responds. After some more work on signal conditioning, it will be ready for use.
This work included the following:
1) Digital circuit design
2) Mechanical design
3) Signal conditioning
4) Human interface design