Sensor change

Although the original plan was to use a laser like system, and to have one sensor positioned either side of the square columns, this plan has now changed. I had previously arrived at the idea of using photodiode, which would act as a light sensor. Unfortunately I was informed that photodiodes would not have work properly considering the lighting conditions, as they would be positioned in relative darkness, and haze would also make their operation even more difficult. As a result I needed to find a sensor that did not rely on light differences, and could operate unnoticeably, unlike lasers, which would be seen once, haze/smoke would pass the beam.

Other options that were available at this stage were infrared, ultra sound, or more simply a detection system similar to PIR (Passive InfraRed). I have researched into the capabilities of infrared and ultrasound during the research stage of previous projects and have found that they can be extremely complicated to implement properly, and require a large amount of knowledge and work, something that might not be achievable considering the amount of time that I have left to complete the rest of the project.

I therefore decided that it would be worth consider PIR detectors, as they were easily obtainable and relatively cheap. It was important however, to consider how they would be able to be controlled and how easily it would be to intercept and interpret the signal that they omit once they have detected motion, basically determining whether they would be suitable to use in the project.