View Full Version : POV levitation-wand project

01-02-2013, 12:19 AM
My weekend project for a new-year party:

- Teensy3
- Transound TSB140 electret microphone and a simple opamp preamp, to the Teensy ADC. Listen to beats.
- Strips of LPD8806 LEDs
- Powered by a single LIPO cell plus 5v booster

All this packed into a 24-inch acrylic wand with 0.6" square inside section. Suspended by a very strong thread from a point just above mid-way. Loop the other end of the thread around a finger. This makes a "levitation wand" -- amazing fun toy for indoor or outdoor entertaining. (Look on YouTube for some examples).

On the Teensy, I'm sampling the audio at ~10kHz, and FFTing (although I didn't yet get useful results, there's a stupid bug somewhere), and also painting text for persistence-of-vision. The LEDs refresh comfortably at >200Hz, which is plenty fast to paint a string of letters in a foot or two of space as the wand moves around.

So, this was a really fun build. My first real chance to play with Teensy3. It was great to get sensible analog values from the Teensy ADC, and also to use FastSPI to drive the LEDs so fast. Quite a massive step above Teensy2 or Arduino hardware. It worked beautifully.

But then I blew it, poking a hole in the LIPO cell as I tried to pack it the very last inch into the tube. Bang. Fireworks :-(

Code, and schematic for the electronics: https://github.com/hughpyle/teensy-povwand
Picture of the burnt remnants: http://pic.twitter.com/XBnRdGJs

Some time soon I'll try again... more safely...

01-20-2013, 05:26 PM
Nice project, a pity it was cremated prematurely, but version 2 always gets better anyway ;-)

I'm looking to add some music-sensitivity to an LED staff I'm working on, and you seem to have done just that. What I was wondering about though, is that my touching and spinning the staff will probably also translate to sound, and this should be canceled out somehow. Without having looked at your schematic or code, did you find a way to do this or was it not a problem for you? I was thinking to use a 7 band equalizer chip like the MSGEQ7 for this, so I'd be picking up just the bassline of the music, hopefully. Or is this something you did in software in the Teensy?

And do you have any links to a video of the wand in action?

Better luck next time, I hope you rebuild it!