INSIDE MOUSEY

How a mild-mannered computer mouse becomes a fast, freewheeling photon-hog.

Analog (non-optical) mice pick up movements of
the ball with two axles that turn gear-like wheels.
The teeth rotate between IR emitters and recep-
tors that capture the flickering shadows to read
horizontal and vertical directions and speeds.
Reverse-biasing the diode emitters
turns them into Mousey’s “eyes.”

Mousey’s bumper (from one of its buttons) empties a capacitor-full of current across a relay, temporarily crossing the motors’ voltages and throwing Mousey into reverse.

Randy Sargent’s Herbie (below) was the first LM386-based bot. It finished last in the 1996 Robothon’s line-following race, but went on to spawn many descendent designs.

The eyes’ light difference is amplified and tapped into the circuit between the two motors, wired in series. As one motor draws less power, the other uses more, steering the bot.