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Chapter 8. Project 2: Mousey the Junkbot > Understanding Mousey’s Brain

Understanding Mousey’s Brain

Where our coat hanger walker made use of the versatile and minimalist Bicore circuit (see Chapter 7, “Project 1: Coat Hanger Walker”), this robot uses a different, but similarly inventive, chip hack. The main component of this bot’s control circuit is the LM386 audio operational amplifier. As mentioned previously, the 386 was designed to boost the signal in certain consumer electronic devices that use small speakers. It “listens” to two input signals and compares them. If one signal is lower than the other, the chip is designed to boost that signal to equalize the chip’s output. Because these inputs don’t have to be sound signals, the op amp can be used to compare other inputs (in our case, light values). If we hook up the output to two DC motors, we suddenly have a little brain that can read the input from two light sensors, compare them, and equalize the output, and use that signal to drive two motors. This gives us a robot that will follow a light source, all the while adjusting power to the two motors to keep itself heading toward that light source.

We then can add further lifelike behavior to Mousey with the addition of electronics that make it become pseudo-photophobic (in other words, it moves away from its light-seeking direction). Our bump whisker will trigger a relay switch that reverses the motors for a few seconds, making Mousey suddenly scuttle away from its previous course.


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