My project will utilize heavily on motion sensors, particularly IR distance sensors. Motion sensing is a passive system that detects infrared energy, known as PIR (passive infrared). In order to detect a person, you need to make the sensor sensitive to the temperature of the human body. So, 93 degrees radiates at a wavelength of about 9-10 micrometers, so those kinds of sensors usually have a range of about 8-12.
The devices themselves are simple electronic components. The infrared light bumps electrons off a substrate, and these electrons can be detected and amplified into a signal. The electronics package attached to the sensor searches for fairly rapid changes in the amount of infrared energy it sees, which means it can detect someone walking by, but not if someone is standing motionless before it.
IR motion sensors are in common use, particularly with security systems. Tracing past the path of a sensor will trip an alarm, alerting security to the presence of no-good-niks. Although, motion sensors normally cannot “see” someone through a window; this is because glass is not very transparent to infrared energy.
In my project, the IR sensor will be at the helm of the robot car (and possible on all sides, depending). When the sensor detects motion, it will trigger the motor in the back wheels and move away from it. If one were to start out approaching the robot from the front (and the way I would set it up, they would), it’s possible one sensor would work, as it would continuously move backwards, but stay in view with whoever is in the room, but if not, more sensors may be necessary to give the robot more acknowledgment of its full surroundings.
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