Ok so here's the scenario:
Up to 200 people sitting on the ground in a marquee at a festival. A talk from various experts (such as Marcus Du Sautoy) is the main focus, following which we will be having a QnA session between expert and audience. We want to incorporate audience feedback using open technologies into the debate, partly as a way to give a voice to the less gregarious members of the audience. The idea we're currently looking at is to have a 'statement and reponse' section in between the talk and the QnA session.
So, what we need is to be able to take a rough reading of the audience reaction for each 'statement' presented to them. Due to the fact that it is situated in a noisy festival, audio capture clearly isn't appropriate, so we are going to ask the audience to stand up or move around as a positive response to a question then we are going to ask the audience to repeat this for the opposite statement, so as to get a fair comparison. For example, how good do you feel Western Capitalism has been for developing nations since WW2? ...then... How bad do you feel Western Capitalism has been for developing nations since WW2.
Ok sorry for the preamble, I know this is an arduino forum, but I just wanted to set the scene properly...
So we're looking at motion detection sensors to sense the overall movements of between 50 to 200 people. What we are looking for here is to get an aggregate of motion occurring, rather than to know exactly where that motion is occurring. They will be mounted either from the ceiling of the marquee looking down, or on the sides looking inward.
I have used infra-red and ultrasonics before, but feel they are inappropriate due to them being proximity based, rather than general motion detectors, and also FOV is often not that wide.
I initially looked at using an xbox kinect sensor (or a few of them), but I believe the 'x, y, z' sensor only has a range of 3.5m. Please tell me if I've been too hasty in writing it off though!?
I wondered about using the Parallax X-band motion detector (datasheet: http://www.parallax.com/Portals/0/Downloads/docs/prod/sens/32213-X-BandMotionDetector-v1.1.pdf
). I have used one of these before to good effect, but I don't know how it would respond to such a large amount of stimulus. Also, 1 detector wouldn't be enough, so I'd looking at using 2 or more... is this even possible? On an old arduino forum posting (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1279812004/all
) someone suggests that there would be confusion between the sensors if more than 1 used, but this is merely a supposition, does anyone know this to be the case?
The other technology I wondered about is either security alarm or cctv technology. Would security alarms such as these... http://www.texe.com/ricochet/products.html
...be suitable, or even usable? They operate around the 800MHz range and are modular, but I don't know how easy it'd be to hack the system to be able to read the output of each sensor for my own purposes... And as for cctv cameras, my friend has some with suitable range and FOV, but all they have as an output is a BNC connector so I don't know how I would then go about interpreting the video image to get an approximate aggregate of motion occurring in the image. Does anyone have any idea about software that could do this?
I know I have strayed away from actual arduino related content massively here, but I am certainly looking at the potential of the xband motion detector, which I would be using with an arduino. If anyone has any expertise/knowledge of the other things I have mentioned, please do respond, otherwise, please don't be offended that I have gone so far off arduino topic!
any help very kindly appreciated