Operation
This second component of our system was tasked with monitoring specific tables and letting the user know exactly how many people were at each one. It employs PIR Motion Sensors we purchased from AdaFruit. The sensors would be placed above each seat at a table and would be able to monitor that particular seat.
Single PIR Motion Sensor
Setup and Design
Our initial designs for a table monitoring system called for a variety of sensors including proximity sensors and ones with cameras. All of these were hashed one after another due to pricing or practicality reasons, and we settled on the motion sensors mentioned above. The sensors (pictured below) had spherical field of view because of their shape. They output 0V when detecting motion in this field or a solid 3.3V when detecting no motion.
Much like the lasers before them, the wiring on the sensors were very weak and not very suited to our application. We had to apply similar modifications. In addition, the unnecessary inceased field of view on each sensor proved to be a headache when testing as our sensors kept sensing objects outside of the area directly below them we wanted them to monitor. After some thought, another trip to the school hardware shop followed, where we successfully limited their field of view using some PVC piping. The illustration below shows this.
Modified Sensor with PVC piping attached, limiting field of view
Front view of modified sensor