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Laser Harp?

Kipkay

Kipkay

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Dec 31, 2007
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Hi,

I just started building the circuits for a Laser Harp. Has anyone here ever built one?

KK
 





I guess it would be mostly mechanical work, right?

You could use a 5mW aixisz and photodiode for each 'snare' - i dont know how many you actually want? From the photodiodes it would be possible to convert the signal to midi and use a pc to generate the sound. I think a simple pic controller would be enough to poll the photodiodes (in matrix if need be) and output the notes to a midi interface.
 
the way it has been done is using a galvo and about 200mw green laser you only need the x or y axis of the scanner and well really there is a lot more involved but check out photonlexicon.com and search laser harp or just harp. all your answer will be there there are a few people that have made very nice ones there. also multi colored ones as well.
 
I've never done it, but if I were to design one, I'd use 1 laser for each string mounted in the bottom of the harp, which would each shine upwards on a photodiode mounted in the top of the harp to detect when your fingers break the beam.

You could even build a circuit to detect how "hard" you're plucking the "strings" by determining how much of the beam you're blocking with each pluck, based on the brightness of the light reaching the photodiode. If you want to play soft, just brushing the beam would be sufficient, if you want to play hard, breaking the beam completely with each pluck would give maximum volume.

It would take awhile to master, but so does playing a regular harp. It would definitely be way cooler to look at , though..
 
It looks like this guy got one working using an Arduino, a scanner, sensors, and...i dunno, I ran out of time looking into it:

http://www.stephenhobley.com/build/

The cheapest Arduino clone I've found is the Stickduino.  $20 for a pre-assembled micro with a USB port?  You can't beat that!

Edit: The guy makes you pay $20 for the complete plans. Meh. I would use mostly-reflective mirrors for what would go out over the audience, and place the light sensor behind it.
 
phoenix3200 said:
It looks like this guy got one working using an Arduino, a scanner, sensors, and...i dunno, I ran out of time looking into it:

http://www.stephenhobley.com/build/

The cheapest Arduino clone I've found is the Stickduino.  $20 for a pre-assembled micro with a USB port?  You can't beat that!

Edit:  The guy makes you pay $20 for the complete plans.  Meh.  I would use mostly-reflective mirrors for what would go out over the audience, and place the light sensor behind it.
Click to expand...

yeah that is one of the members over at pl he is very willing to help in anyway with the laser harp.
 
ElektroFreak said:
I've never done it, but if I were to design one, [highlight]I'd use 1 laser for each string mounted in the bottom of the harp, which would each shine upwards on a photodiode mounted in the top of the harp to detect when your fingers break the beam. [/highlight]

You could even build a circuit to detect how "hard" you're plucking the "strings" by determining how much of the beam you're blocking with each pluck, based on the brightness of the light reaching the photodiode. If you want to play soft, just brushing the beam would be sufficient, if you want to play hard, breaking the beam completely with each pluck would give maximum volume.

It would take awhile to master, but so does playing a regular harp. It would definitely be way cooler to look at , though..
Click to expand...


doesnt he makes it resonate when he moves his hand up and down while braking the beam??? (i saw it on youtube) its gotta be more complicated than that... im sure he uses more sensors than just photodiodes.
 
chIno said:
[quote author=ElektroFreak link=1228228911/0#5 date=1228236266]I've never done it, but if I were to design one, [highlight]I'd use 1 laser for each string mounted in the bottom of the harp, which would each shine upwards on a photodiode mounted in the top of the harp to detect when your fingers break the beam. [/highlight]

You could even build a circuit to detect how "hard" you're plucking the "strings" by determining how much of the beam you're blocking with each pluck, based on the brightness of the light reaching the photodiode. If you want to play soft, just brushing the beam would be sufficient, if you want to play hard, breaking the beam completely with each pluck would give maximum volume.

It would take awhile to master, but so does playing a regular harp. It would definitely be way cooler to look at , though..
Click to expand...


doesnt he makes it resonate when he moves his hand up and down while braking the beam??? (i saw it on youtube) its gotta be more complicated than that... im sure he uses more sensors than just photodiodes.[/quote]

I'm sure it is more complicated than that, especially since I have never built one myself, but the effect you describe could most easily be accomplished using a sustain pedal from any MIDI keyboard setup. Also, I'm sure that the sound that the audience hears has been run through a few effects processors, so you wouldn't b able to tell what's coming from the harp and what's coming from the effects processors.

Also, a scanner would definitely work as well (or any other method of generating several beams at once on the same plane). I think that the most important feature of the laser harp would be the photodiode arrangement, and the circuitry used to process the signals generated by the photodiode array..
 
Ahh...you don't necessarily need to have remote sensors.

You use some type of sensor in the unit to read the reflected light from different points where the laser beam would go.  Based on the falloff and the relative absorption/diffusion of the material that interacts with the light, you can calculate the distance to intersection based on the detected light intensity.

This idea isn't nearly complete (e.g. what if your hand was only partially blocking the light), but it's a start.
 
phoenix3200 said:
It looks like this guy got one working using an Arduino, a scanner, sensors, and...i dunno, I ran out of time looking into it:

stephenhobley
Click to expand...

Yes, Stephen is the one who built the one in MAKE Magazine which is what I am working on. Pretty complicated. It uses IR sensors to detect where your hand is and yes, does use MIDI.
 
Well, if you want the beams to shoot out the top of the harp, reflections seem the only feasible way to detect if a finger is in the beam... that would complicate things, but i'm sure it could be done.

If you use a scanning arrangement for the beams, you dont need to detect where the hand is, just if it reflects any light at all. Which 'string' is touched can be determined from the timing of the scanning system. The detector itself would take some optics to construct i guess - and a lot of tinkering.
 
Hej KipKay!
I'm also attempting to make the make version of the harp. I have had good google around to find out other ways of putting it together as well.

I would love to know how you mounted the laser modules in order to get them end up nice and parallel to reach the sensors.... think this is tricky and i could fix it with duct tape but I'm looking for a more handsome solution. (i've made small holders in aluminum with screws to adjust but it's still tricky as hell).
The big benefit with S.Hobleys harp in the control you have through programming the galvanometer and decide the beams distance.

I'm going to use 2X4051 multiplexers to get more inputs to the arduino.

Good luck with the making.

/A.
 
I have been thinking of a slide guitar type build using a chrome bottleneck to divert the beams onto photo diodes, early days as there are too many other projects in the works at the moment.

Regards rog8811
 
To all:
His DIY videos are simple and rudimentary, that's what makes him so popular. If the project involved IR sensors, PIC micro controllers, and MIDI, noobs will be intimidated.

To Kip:
Just use some CDS cells to detect the change in light. Resistance goes up when CDS cells are in the dark so you can use their output to trigger a PNP transistor to act as a switch to a hacked electric toy piano key.

Just an idea ;)

-Tony
 
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