As part of the Brighton Fringe Festival, BuildBrighton have been invited to take over the
Ocean Rooms on Sunday 8th May 2011. We're creating a number of sound- and light- installations for an evening of eletronic music madness.
Of course, the most visually impressive light-to-sound instrument for electroncia is Jean Michel Jarre's Laser Harp. There are quite a few
homemade harps around (on Youtube and the like) but even the cheap ones are relatively expensive. The problem is, to get a visible laser beam, you need lots of smoke and something substantially more powerful than
a laser pointer off eBay!
I looked into getting a powerful 250mW+ laser and using a galvo to draw the vertical "strings" for the harp - if you look closely on some of the YouTube videos, you can see that this seems to be the current approach as some strings appear to have a bit of flicker (the flicker isn't noticeable when played live, it's just the way digital cameras pick up fast-moving images).
Something like this
Light Harp would be very impressive to make too - I love the idea of using some really old retro radio cabinet to house such a cool, futuristic instrument. Using lights instead of lasers also makes it much safer to use in a public space (and encourage the audience to have a go themselves). It plays like a real harp too - with the user "plucking" the light beams to trigger a sound.
The
photos and schematics show that a lot of work went into this particular instrument - and the build cost was around $500, a little bit too much for many people to have a got at. In short, it's an amazing instrument, but too expensive and too complicated to try to explain at a single-night event.
What we need is something a little simpler.
Almost all homemade laser harps use some form of LDR (light dependent resistor) and a break-beam sensor to detect when a user has placed their hand over a light source. The laser beam hits an LDR, making the internal resistance low. When a hand breaks the beam, the resistance of the LDR increases and the controller recognises that the user has placed their hand in the beam.
Lasers have a nice, concentrated beam and are relatively easy to work with. LEDs and other diffused light sources are not quite so simple - light can come from a number of sources to strike the LDR, not necessarily from an LED placed over it.
While searching the 'net for "pinhole" lenses (to see if it is possible to narrow a beam from an LED) I came across
someone who had a similar idea; only to turn the problem on it's head. Instead of trying to detect reflected (or broken) beams of light, Peter uses a series of light dependent resistors and a pin hole to create "cones" of detection, basically checking for the presence of shadows, as you wave your hand over the instrument.
It's a brilliantly simple but effective idea.
I think it's a project that we should be able to get up and working in a couple of days - and simple enough to create kits for other users to make their own, ready for a "big band ensemble" for the Fringe Festival!
