I just found this clip on Youtube - awesome!

It makes me really happy to see that someone has got the plans working - great stuff.

I’ve been asked to write an article for Make magazine on MIDI controllers using lasers and light. It’s come at the right time, as I’ve been meaning to try out the Sharp GP2D12 sensors I bought from Trossen Robotics. Anyone that has played a Roland synthesizer with a D-Beam controller will recognise these immediately. They fire out a pulse of IR light at 25Hz and then triangulate the position of the reflected dot to get a distance measurement.

Having played around with them for a while, there are two problems that need to be addressed before they can be used for musical applications:

The first is that the output can be noisy - this is in part due to the fact that quite a lot of current is drawn every 40ms when the IR LED is fired - this can get into the output signal as a spike. First off a 300uF tantalum cap and 0.1uF regular cap can be put across the power rails close to the sensor input - this helps to smooth the power going in. Additionally this basic filter circuit can be put across the output to smooth out any remaining spikes.

[Circuit -coming soon!!]

Also only sample the output every 40ms or so, as the output is only updated this often. It’s also possible to filter in software like this:

forever
{
while (!sample_available())
{
do_something_else();
}

average = (average < < 3) - average + get_sample();
average >>= 3;
// do something with the average here

}

This gives each sample an exponential decay.

The second problem is that the output from the device is non-linear - so we need to apply a ‘linearization’ to the output. Thankfully someone has already done the hard part for us - the functions are as follows:

GP2D12:

Range (cm) = (6787 / (V - 3)) - 4

GP2D120 (long range):

Range (cm) = (2914 / (V + 5)) - 1

[Taken from http://www.acroname.com/robotics/info/articles/irlinear/irlinear.html]

Applying this function as either integer or floating point math helps in getting a value that can be further scaled to modify MIDI pitch bend (0-16383), or continuous controller information (0-127)

One final tip - be careful where you place the sensors - putting them too close to a side wall, or in the wrong orientation can affect the reading accuracy, but when used properly these are a valuable addition to any MIDI hackers toolkit.

Last night we went shooting some footage for MakeTV and moved the harp to Anton Phibes’ secret underground lair..*

This was the first time we’d had harp set up in a proper venue, and it looked pretty amazing. We also took along the my homemade display scanner for a bit more p’zazz.

*Google:The Abominable Doctor Phibes

Skip Russell emailed me to send me this link to his pictures from the Maker Faire - great job, as the lasers are not easy to capture on camera…

http://www.flickr.com/photos/skipr/tags/laserharp/

Looking at the EXIF data, it was 18mm, at 1/5s F3.5 - not sure about the ISO, but I should imagine it was set fairly high. Short exposure time and center-weighted metering help to capture the swirling fog patterns quite nicely…

Everyone loves the laser harp…

Good Morning America stopped by the booth to film the harp…

Kudos for Pete for having his camera ready…

We just finished two intense days at the San Francisco Maker Faire. Had the harp set up in the Dark Room hall. By the end of the show Pete and I had just about worked out how to run the booth and drum up a crowd.

Most people just loved to look at the harp, rather than play it. I think a few were disappointed that the notes were on a preset scale and not a musical scale - so next time we’ll have to fix that.

There’s another Faire in Texas later in the year, and all being well we’ll be showing at that one too…

Some of you might have noticed that I received unsolicited comments in my YouTube channel regarding the laser harp that’s currently being sold at Sharper Image.

If the over-zealous marketing team had actually approached me first then I might have been more inclined to work with them. But instead they left me with no choice but to delete the comments they had inserted.

If you’ve not seen it, it’s quite… err… interesting…

Click Here to View

Of course, denizens of the ‘net community couldn’t let something as unintentionally amusing go without a releasing their own “mix”…

So anyway I thought I’d better go take a look at this thing. So I called in at Sharper Image yesterday to play the light(tm).

Having watched the video a bazillion times I felt fairly well qualified to get something musical out of the device, and after a few minutes of playing I was pleasantly surprised as to how well the software was able to “pick up” on my musical ideas. Some of the songs are better than others - but music is a subjective thing after all, so your mileage may vary.

The construction is plastic and a little on the weak side, I wouldn’t want to do any serious gigging with this thing. But then I suppose it’s not intended to be hauled around constantly in the back of a truck.

At $599 the price point seems a bit high, and some of the people I talked to in SI seemed to agree. $399 is probably a better price, and well within the discretionary income band.

The only problem I can see is that this is not teaching you to play a musical instrument. The Yamaha WX-5 wind controller ($599) for example can teach you the correct finger positions to play a saxophone, flute, or clarinet.

I was told by one of the investors that there will be a music authoring package available for the Beamz - and this I think is going to be essential for the long term appeal of the product.

WFYI is the local PBS station here in Indianapolis.
They ran a story on my laser harp project.

If that’s not an example of how good lighting can make you lose 25lbs then I don’t know what is…

Frets on Fire + GlovePIE + Laser Harp + uncoordinated doofus…

They said “Do FREEBIRD!!!”

…so I did.

I’m sure I can sell Sharper Image on this one…