BEAM Robots [1] were some of the first robots I ever created in the late-90s. They were extremely accessible to someone still scraping together allowance and ri

BEAM Robots [1] were some of the first robots I ever created in the late-90s. They were extremely accessible to someone still scraping together allowance and riding their bike to radioshack for parts. The photovore was one of the earliest designs I copied. It always astounded me how much the simple analog circuit "brain" made the robot's behavior appear complex and bug-like. Stripped down to the bare essentials, the simplest photovore circuits [2][3] work by setting up a voltage divider between two photoresistors positioned like eyes on either side of the robot's body. The output is fed into an inverter based oscillation circuit biased by the side of the robot light is coming from. This runs through some more inverters in parallel to step up the current high enough for two tiny motors with wheels. It creates a robot that waddles towards the brightest light in the room. The simplicity of the circuit makes the various emergent robot behaviors that much more surprising and interesting. The frequency of the oscillations get faster in brighter light and slower in dim conditions, almost like the robot is searching harder to find the light in a dark room. If one wheel gets stuck, the torque stalling motor backfeeds into the control circuit and it can sometimes jolt or vibrate itself unstuck. If you power the whole thing with a solarpanel that charges up a capacitor for bursts of runtime, the robot really seems to come alive as it wiggles it's way towards the light imperative that keep it's circuits fed. There is something magical when you see a robot struggling to stay alive. [1] https://en.wikipedia.org/wiki/BEAM_robotics https://en.wikipedia.org/wiki/BEAM_robotics [2] http://solarbotics.net/library/circuits/pix/4_comp_pvore.gif http://solarbotics.net/library/circuits/pix/4_comp_pvore.gif [3] http://solarbotics.net/library/circuits/bot_popper_240.html http://solarbotics.net/library/circuits/bot_popper_240.html