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### Topic: Sensor advice for 360º chandelier artwork (Read 1 time)previous topic - next topic

##### Jan 28, 2012, 10:44 pm
Greetings.

We're a couple of artists looking to create a large, chandelier-like sculpture in the ceiling of an outdoor rotunda (8 metres in diameter and 4½ metres high).

Visitors can walk underneath, approaching from 360º.  As they do, the chandelier's LEDs will change colour.

A sensor would need to determine how close to the centre the closest visitor is at any time.

Before we can go any further, we need to find out if there's some kind of sensor that's capable of this?

We'd be extreeeemely grateful for anyone who could point us in the right direction!!

Many thanks,

#### robtillaart

#1
##### Jan 29, 2012, 12:16 am

make a tile floor filled with pressure sensors. If a tile is pressed let set a flag.

The arduino then can see where the people are, the one closest to the center (distance = sqrt(x^2 + y^2)  but also which part of the floor is crowded, detect movement from tile to tile etc. You can even let the tiles light up (pulsing, vibrating etc)

hope this helps,
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

#2
##### Feb 01, 2012, 05:00 am
Thanks Rob for this suggestion.
We'd thus-far been looking only at techniques that involved overhead sensors, but this is good food for thought!

#### robtillaart

#3
##### Feb 01, 2012, 09:47 pm

- multiple laserbundles ("tripwire") could do the trick, but then you should be able to do a "wave" and have mounting points.

- A webcam from above, compare the image with an "empty room", people will appear as changed pixels.
calculate the distance of the changed pixels to the centre pixel  and take the minimum distance
[pseudocode]
Code: [Select]
`  min = 1000000; // big number  pixel = (0,0);  for each pixel of the image  {    if (pixel != referenceimage.pixel)    {      d = distance(pixel, center)      if ( d < min)      {        min = d;        pixel = (x,y);      }    }  }`

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

#### DuaneB

#4
##### Feb 02, 2012, 07:21 amLast Edit: Feb 02, 2012, 08:55 am by DuaneB Reason: 1
Hi,
It might not be suitable for your space, but if you could it would be great to increase the level of user interaction by making it sound triggered. Most people would be happy to watch someone else change an LED Effect by walking up to it, but get people clapping, stamping and calling and they will all be at it - my kids would make me go back every week.

Just an idea, other than that, the web cam is an excellent suggestion,

Duane B

rcarduino.blogspot.com
http://rcarduino.blogspot.com/2012/04/servo-problems-with-arduino-part-1.html
then watch this
http://rcarduino.blogspot.com/2012/04/servo-problems-part-2-demonstration.html

Rcarduino.blogspot.com

#5
##### Feb 05, 2012, 11:34 pm

Thank you gentlemen for your excellent suggestions.

Duane, the interactivity-by-sound idea's a nice one but there are houses near to the rotunda and the installation's at night, so it might put a few noses out of joint!

Rob, I think you may have solved our problem with the webcam idea!  We were worrying we'd have to go with a complicated system of heat sensors or somesuch, but actually a webcam would be ideal (assuming that we have enough light on the interactive area to avoid problems with gain/video grain creating false signals).

Many thanks once again!

#### darki03

#6
##### Feb 06, 2012, 10:41 am
Hello !

When i saw your project description i have immediatly thought about ultrasonic range-finders. I used them during my studies in a "mini-drone" project for obstacle detection and it works very well !

You can use few of them (depending on the beamwidth) around the chandelier (some sensors are equipped with an I2C bus giving the range directly in different units : http://www.robot-electronics.co.uk/htm/srf08tech.shtml).

Maybe it can work with your project !

Good luck
Bon sang ! mais c'est bien sur !

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