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[on:]

Hello,

I am working on an art installation that reacts to the number of people viewing it.  I need it to somehow determine the amount (the specific number is irrelevant) of people that stand in front of the object.  The highest number of people viewing the piece at any given time should be between 5-10, at a distance no greater than 2-3 meters.

So far I am thinking of using a MLX90614ESF-AAA Infrared Temperature Sensor 90° FOV (~$25) to determine the average temperature and as people walk up to the installation their body heat will be detected and the art will react accordingly.  I am not exactly sure how this sensor works in the real world and perhaps this more expensive alternative would be better: MLX90620   FIRray:16X4 Far InfraRed Array (~$80)

If anyone has any suggestions on if either of these would or wouldn't work or if I need to go about a completely different method, you opinion is Greatly appreciated!!

Thanks!
-Greg

[Reply #1 on:]

You could start with the MLX90614, that's hard enough to detect the number of people.
The temperature you measure depends on the temperature around. On a cold day it is easier to detect people.

I suggest to combine a few sensors.

At least add a PIR motion sensor. You could even use two of them, on the left and right side of the art object. You could use more PIR sensors, like a row of 5 or 7, and shield the front with a small opening for a small beam.

Ultrasonic sensors can measure the distance. For example the ping))) modules. Perhaps you should use just one. I don't know if the ultrasonic sound will interfere if you use more than one.

Some radar motion detectors are not expensive. But you need the complete module with variable sensitivity, not the radar elements without amplifier (as sold on Ebay).

A theramin is something that senses if someone is very close : http://en.wikipedia.org/wiki/Theremin

Measuring the weigth of the people in front of the art object with a weigth sensor in the floor is out of the question ?

[Reply #2 on:]

Or simply place a number of pressure sense pads  (as used in security sensing) on the floor.  The more people there are , the more pads are active.  Then totalise the pads to determine the number of people.

[Reply #3 on:]

I would suggest several PIR detectors pointing in slightly different directions.

I have no idea whether this will work,  but cheap to test.

[Reply #4 on:]

The pressure sensors on the floor would work, I was just hoping the artwork could be self contained and more elegant (since pressure pads on the floor would tend to stand out).  Perhaps if I could disguise some pads to appear not a part of the artwork then the 'magic' of the installation can be returned. 

I don't know if motion sensors would work, since theoretically after people walk into the room they would stop and look at the piece for a couple of minutes.  What I want to sense is the amount of people, not the amount of motion within the space.

Perhaps some kind of sonar??

Summary: Looks like I need to do some testing. 

Thanks for your help so far!