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+

+

1

2

3

4

8

7

6

5

Left motor +

-

4 13

6 11

8 9

- +

Right motor

Relay

6. UNDERSTAND MOUSEY’S BRAIN Use this diagram as a The LM386 op-amp, the main component reference as you build of Mousey’s control circuit, “listens” to two input your mousebot. signals. If one signal is lower than the other, the chip A larger version of this boosts that signal to equalize the one output. In our ^{image can be found at} case, the inputs are light values rather than audio. ^{http://xrl.us/fkxi.} If we hook this output to two DC motors, we have a little brain that reads input from two light sensors, compares them, and boosts the power on the dimmer side. This creates a robot that follows a light source, auto-correcting itself as it moves.

The bump switch triggers a relay that reverses the two motors’ inputs for a few seconds. This makes Mousey scuttle away from light after any collision, adding to its lifelike behavior. The diagram above shows the circuit diagram for Mousey’s brain.

BEAM ROBOTICS: SURVIVAL OF THE FUNNEST

Mousey comes out of the BEAM design tradition, a biology-inspired doctrine which frowns on microprocessors in favor of simple analog control, in order to create robots that act and react with the physical world directly, perhaps instinctively.

BEAM’s natural selection process occurs at conventions and gatherings like Robothon, where bots compete against one another in races, “sumo” matches, high jumps, rope climbs, and other Olympics-style events.

Through BEAM's 14 years of evolution, BEAMers worldwide have designed and refined numerous species of inexpensive and easy-to-build robo-critters, including photovores such as Mousey, four- and six-legged walkers, sun-powered solarollers, and swimming aquavores.

Mousey's circuitry is based on Randy Sargent’s line-follower bot Herbie, which competed in the Seattle Robothon in 1996. Many variations of the design followed,

including Dave Hrynkiw’s Herbie Photovore. Following Dave’s example, we built ours with as much techno-junk as possible, including an old computer mouse and a 5-volt double-pole, double-throw (DPDT) relay − a component found inside most analog modems.

BEAM Resources

The acronym BEAM stands for “Biology, Electronics, Aesthetics, and Mechanics” and was coined by Mark Tilden.

Solarbotics: The main BEAM portal Solarbotics.net

Yahoo! Groups: BEAM Robotics groups.yahoo.com/group/beam

Robothon: Seattle, Oct. 8-9, 2005 robothon.com