Laser Harp

Read this article in MAKE: 15: Music, Page 64.
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Play strings of light, using laser pointers, rangefinders, photocells, and Arduino.

Photos by Jacques De Selliers, Stephen Hobley

Analog multiplexor:

AIN Kit (32 analog inputs) from http://www.avishowtech.com/mbhp/mbhp_ainR4.html

This uses 4 standard 4051 analog multiplex chips – documentation is available on the internet on how to use the control lines to connect to each of the 32 inputs.
[www.arduino.cc/playground/Learning/4051]
[http://little-scale.blogspot.com/2007/06/arduino-midi-out-example.html]

Note: With some clever programming you can use just the analog multuplexor to drive the laser harp – connect the outputs of the photocell array directly into the inputs of this board, then you can detect if a beam is broken in software inside the Arduino.

Digital Multiplexor:

DIN Kit (32 Inputs) from http://www.avishowtech.com/mbhp/mbhp_dinR5.html

This kit uses the 74HC165 chips these take the parallel input lines and create a serial stream, you can chain these modules together and have as many inputs as you need. Documentation is available online - the Arduino playground is a good place to start.
[www.arduino.cc/playground]

-=-=-

More than anything this project has been a testament to the collaborative power of the Internet. I could not have done any of this without the help of many people – who were good enough to answer all the questions I posted on a variety of forums. I'd like to take this opportunity to pass on my gratitude - please keep up the good work! If you want to tackle a full sized scanning laser harp – then more information can be found on my website www.stephenhobley.com.

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