hi
I am working on building a crystal ball for an upcoming performance, kind of like the ones that wizards have except this one will be fitted with a wide angled lens projector into the bottom and be filled with smoke. The projector will be connected to Ableton and play back prepared video and audio footage into the crystal ball. I want to add an interactive element in the form of motion/ distance detection. So that as the performer moves his hands towards the crystal ball a sensor translates the data to control the brightness of the lights in the space and also send Midi CC data to ableton in order to control the volume and opacity of the video clip. I have been looking at using ping))) ultrasound sensor which seems like it would do the job but have been also suggested the use of an infrared sensor, since the distance it needs to measure is not that great. My concern with the IR route is that since the sensor will be inside the crystal ball (a spherical glass streetlight) it might not read the movement correctly through glass.
Lastly - with regards to the ultrasound sensors - I have found quite a few online and the ping))) ones are pretty dear, would one like http://cgi.ebay.co.uk/Ultrasonic-Sensor_W0QQitemZ220414899824QQcmdZViewItemQQptZUK_ToysGames_RadioControlled_JN?hash=item3351c07670&_trksid=p3911.c0.m14&_trkparms=72%3A1683|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50 do a similar job?
thanks for any help
You do realize that putting the ultrasonic sensor inside the ball won't work, right?
That sensor on ebay looks like it ought to work, but that's just a guess. I noticed that the seller mentions Arduino stuff in the description, so I'd send him a question via ebay about what success he's had if I were thinking about buying one.
Here's a project i just saw posted in the "Exhibition" section that might be of help to you:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1243154560
Ran
yeah - i was thinking about this last night and realized that the ultrasonic sensor would have the same problem as the IR. Does anyone have any suggestion for a suitable sensor that could detect distance measurement through glass?
thanks for that link - looks like a fun project!
Perhaps some sort of capacitive sensor, with a very fine wire on the globe?
Do a google search for "theremin antenna": you might be able to do something based on a theremin's frequency output. The "minimal" (pitch-only) theremin that pops up on the first page of results might be just the ticket. It's designed for a big antenna, but it might work with a small wire if you don't mind having to bring your hand close.
Do you have a picture/drawing of the setup? I'm thinking you might be able to put the sensor in the base.
Maybe one of these:
http://www.acroname.com/robotics/info/articles/sharp/sharp.html
Ran
the capacitive sensor approach is really interesting but from what i can tell it works only at very close proximity and I need the device to be sensitive from around 50cm away. The only thing i can think of at the moment is if the sensor is somehow above the glass sphere and measures the distance going away from the sensor.
i have attached a (crude) illustration of what I am trying to build. 