Turning Mechanism
Our goal is to control the robot's path of travel. The front bumper appears to be the primary mechanism which controls the robot's turning behavior. If we can tap directly into the back end of the sensor, we should be able to directly signal the robot via "virtual bumps".
We disconnected the left navigation motor's wire harness which which gave us access to the left bumper contacts. Instead of the Hall Effect sensor that we were looking for, we found an ingenious IR emitter and phototransistor assembly.
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When the front bumper is actuated, the grey pushlever covers the IR emitter hole. This caused a change of potential of 5 Volts on the Collector contact of the phototransistor, signalling the processor that a bump was encountered.
The Anode had a constant potential of 1.25 Volts.
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We then implanted two wires on the Collector and Emitter contacts of the phototransistor to enable us to send "virtual bumps".