An EECS 373 project by Jason Conn and Sam Wintermute, the Hypnotoad is an interactive toy. Upon startup, the Hypnotoad will enter a "scanning" state, where it will attempt to locate the closest object. Once found, the Hypnotoad will then turn towards and attempt to "hypnotize" the object by persuasively spinning its eyes with a speed relative to the distance of the object. Once the object moves out of range, the toad will make an attempt to re-find it and if it fails, will return to the "scanning" state.
Behind the ultra-realistic exterior of the Hypnotoad lies a plethera of cutting-edge electronics. The toad "sees" via an Ultrasonic Ranging unit discreetly integrated into its collar. To take a measurement of distance, a pulse is sent to the unit while a timer is simultaneously started. Upon receiving an echo pulse back, the timer is stopped and the timer value is read and converted into inches. The hypnotoad makes approximately 10 such ranges over a radius of 90°. The rotation of the toad is controlled by a small servo motor at the base, which in turn is controlled by a software driven pulse-width modulated signal (PWM). Two "dumb" motors lay behind the eyes, their rotation also controlled by a PWM signal, this time in hardware. The supporting hardware is a standard EECS 373 board, with a Motorola MPC823 processor and FPGA.
Difficulties encountered during the creation of the Hypnotoad mainly stemmed from the Ultrasonic Ranging unit. One of the problems
lay in the calculation of thresholds; for example, how close should someone be to the toad before the toad "sees" him or her. We had to balance the
desire to "see" further with the reality of mistakenly picking up stationary objects that may have been closer. Another difficulty
that we encountered was the interference induced by the motors for the eyes. At high speed, they would create a sizeable electromagnetic
field, and this would cause the ranging sensor to inadvertantly fire. This problem was solved by masking the interrupt that controlled the ranger
when we were not explicitly using it.