Saturday, July 19, 2014

The Humboldt Laser Harp Project: Part 2

So, I'm still glad I'm part of the Humboldt Laser Harp (HLH) project. But boy do I feel useless and clueless about what's going on from a technical standpoint...
SparkFun MIDI breakout board

There have been a few emails back and forth today between Ed, Nick and me about the HLH project. Ed's getting a lot of the programming concepts figured out, e.g. "...I think I've solved (assuming that any of this actually talks to a MIDI thing, anyway) the 16 string limit. The 16 MIDI channels are now dynamically assigned to different strings as needed, and released when the string is released. Not sure what would happen if you broke more than 16 beams. Probably the beams >16 simply wouldn't be played. Currently the notes have a hard cut on the end of them rather than a fade...I'll work on that if/when I have a sudden flash of insight. The number of analog input pins are the only limiting factor for the number of strings now. Given external comparators or an external (fast) ADC or analog multiplexer an Arduino could do a ton of strings with more or less this same code..." Nick is doing his part by pulling apart a laser and 3D printing a holder for the laser so we can easily fine tune where the laser is pointing. He's also going to dig up a USB MIDI input for Ed to use during the design phase of this project.
SDS-50J MIDI connector

Tonight Ed evaluated using a SparkFun MIDI breakout board vs. the SparkFun MIDI shield vs. rolling his own MIDI connection. He decided to roll his own, and at this point, all he needs is a CUI Inc SDS-50J MIDI (DIN 5 pin) connector and a Lite-On Inc 6N137 optocoupler. He's ordering those from Digi-Key, for a total of $1.78 plus shipping. Here's the optocoupler datasheet link if you want to read up on that.

Me? I'm mostly reading the emails about what they're doing.

6N137 optocoupler
Oh well, The important thing is a laser harp MCU device is being designed, the Humboldt Microcontrollers Group has launched their first group project, and we'll end up with v.1.0 of what will eventually be an interesting example of what you can do with MCUs.

Returning to the HLH launch meeting we had yesterday, here are a few other points about the project as it currently stands.
  • The laser harp will be the 'framed' style rather than the 'unframed' style. See the two pictures below.
    Unframed laser harp
  • The tentative height of the v.1.0 harp is 36 inches. The laser harp frame will probably be placed on a table when it's exhibited in public, and probably on a somewhat lower stand when a laser harpist is sitting in a chair playing it. The width will likely be between 36 and 48 inches, so that it's portable, so that an open horizontal hand can easily interrupt just one beam without accidentally breaking an adjacent beam, and so a laser harpist can comfortably reach all the beams.
  • Nick will provide computer speakers, a MIDI sequencer and an amplifier.
  • The goal of this project is to make a musical instrument, not just an electronic tone generator.
  • Yesterday's post referred to the Electronic Light Orchestra. The reason I used the word 'Light' in that descriptive name is because:
    • When the laser harp is in a dark environment, the laser beams will be a light source.
      Framed laser harp
    • Nick has a color organ we will work to integrate into the HLH. The light organ has RGB LEDs that change intensity and color in response to music (audio frequency range) and the settings of the organ.
    • If I understood Nick correctly, we may also try out incorporating some background laser light show effects with the HLH.
  • One aspect of the laser harp we need inspiration and a bit of technical expertise, or at least some creative thinking, is 'laser beam presence enhancing.' I hope that term is self-explanatory, but the issue we need to address is how to make a low-powered laser beam most noticeable by a person if the laser harp is not in a very dark environment or if the person playing the harp is not looking closely at the laser beam. Some of the enhancing techniques we've discussed are:
    • a fog machine, especially some type of 'fog' generator that specifically is generating or concentrating fog in the area where the laser beams are.
    • a black 'booth' or mini-pavilion that can be set up to enclose the laser harp and make the laser beams more visible.
      Fog machine
    • an air pulse generator that would put a concentrated air stream in the same location as the laser beam.
    • a water jet that runs in the same area as the laser beam.
    • Some other type of haptic signal that the laser harp player would feel when their finger or hand was breaking the laser beam.
  • I'm going to research laser safety issues to make sure we understand what laser strength or power is acceptable for use with the general public so we don't have anyone get burned by the laser (skin or eyes).
Enough for tonight. More HLH posts will be showing up over the next couple weeks. Maybe Ed or Nick will have something they get so interested in whilst working on their parts of the laser harp that they'll feel compelled to write a blog post or two!


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