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Topic: Laser Harp - Safety Concerns (Read 1 time) previous topic - next topic

boguz

Hi

Now that my Arduino MIDI Footcontroller project is ready and working  8) it's time for me to start thinking about the next project.
Hmmm, well, actually i have already been thinking about it for quite some time.

I would like to make some kind of Laser Harp.
I searched here in the forum and in the internet, and there are many pages talking about it. I have read through many of them, but as a beginner i have some concerns about this project. I would greatly appreciate any advice you can give me...

So, for what i can gather, there are two main kinds of Laser Harps:
   - those super cool made out of really powerful Lasers (you can see the "strings" and all);
   - and those made out of weaker lasers, or even photosensors (you cannot see the "strings").

The thing is, and i think most of you will agree with me, what makes the laser harp cool, are those laser beams and the way you can interact with them to play some music.
That being said, i have also read in many pages that they can be very harmfull to your eyes. Hmmm, i kind of like my eyes, so i would rather if no harm would come to them!  ;)

My question is:
What would be a good compromise between having some super-cool-laser-strings-awe-inspiring-harp and a safe-and-working-but-kind-of-boring harp?

I have NEVER worked with lasers and i also don't know many other alternative ways to do it. Some ideas that come to my mind (and that i have seen on other websites)
1) Super powerfull laser
2) Weaker laser (like a laser pointer) directed to a photo sensor   <--- maybe the most doable?
3) photo sensors?
4) IR sensor?
5) distance sensors?

As i said before, the idea would be to built an Arduino based Laser Harp, as cool as possible, but keeping it safe (to build and to play)!
And all your inputs are very welcome.

Thanks you!
=)

AmbiLobe

Place a fog machine above the lasers. Allow the fog to drift on still air, downwards so that tha laser illuminate the fog.
I am going to get going.

radman

Quote
Place a fog machine above the lasers

That is my idea, you stole my idea  :)

Really powerful lasers will cut steel so you don't want to put your fingers in those. You can pick an appropriate class of laser for your application though http://en.wikipedia.org/wiki/Laser_safety.

There have been real accidents. I am sure I recall people being blinded at a disco or some such event by a laser.

Even with a low power laser I would avoid looking directly at it and also avoid rings and things that might reflect the beam. The main risk would probably be children sticking their heads in and peering at where the "strings" come from.

Surely harp strings have to be plucked? Does where the string is plucked, the plucking technique and the strength of the pluck not all matter? How does a laser harp cater for this?

mrburnette

What would be a good compromise between having some super-cool-laser-strings-awe-inspiring-harp and a safe-and-working-but-kind-of-boring harp?

Consider using plastic fiber optic pumped by a super LED or LASER.  You get a nice glow at the refraction boundary.

I did some extensive laser experiments with units from 5mW to over 1000mW a few years back.  Avoid the higher energy lasers for safety reasons, they can be quiet dangerous.  Even at 5mW, a laser demands respect since different wavelengths can have radically different affects on eyes.

Reference: http://ohp.nasa.gov/conference_info/conf_gen/presentations/2013/ohconf/pdf/Kim_handheld_lasers_NASA_OH_meeting_2013.pdf


Ray

mirith

Unlike in movies, laser beams are generally not visible without something to reflect off of, for example, the fog machine idea (which is probably the best idea).  Now the problem is that when it passes through something like fog, it will lose power, so don't over do the fog or the fog will start playing your music for you.

boguz

thanks guys.

well, the fog machine sounds like an idea that would work. But i think it is very unpractical.
Maybe it is better stop dreaming about seeing those "strings" and thinking about something that will actually work well!  ;)

What about "non-visible-string-harps", what would be a good idea?
What kind of sensors would be good?

I am afraid that those light sensors will work differently for instance while playing in a park outside on a sunny day and playing inside in a dark concert room.
Any ideas?

radman

Quote
well, the fog machine sounds like an idea that would work. But i think it is very unpractical.


Hmmm. Are we talking about playing in private or giving a performance? If you can play the harp with invisible strings great. Imagine the dramatic effect of mist poring down a harp during a performance though?

As to practicality when I was young ice-cream was delivered in insulated boxes packed with dry ice (solid CO2). What a joy to take the dry ice, dump it in a sink add some water and create a two foot thick fog on the floor. Of course in those days children were allowed to play with solids at -60C before health and safety spoiled all the fun.

boguz

i have also seen that there are a couple of cheap ways to make smoke, like this one:
http://www.youtube.com/watch?v=exKNbK7teQs


Quote
Are we talking about playing in private or giving a performance?

I do play in a couple different groups/bands. in one we play classical music and in the other we play a little bit like klezmer/gypsy/fun music.  8) I can imagine that if a project like this would turn out well, i would maybe use it for our klezmer band, but i would mainly use it at home and to have some fun in our jam sessions.

So, let me ask you guys a question:
What would be the safest usable (hmmm, cheap!) laser for this kind of project?

I don't know anything about lasers. i have started reading about it, but i am having trouble "deciding" anything on my own. i'm kind of afraid actually...    :smiley-red:
I think a laser from Classes 1 and even maybe 2 would be ok. Class 2 goes up to 1mW. I'm not so worried with the color...
Would it be better to get a laser diode and build a circuit for it, or could i actually buy some laser pointer and use those parts (i have seen some laserpointer a lot cheaper than laser diodes...)

Is this a project for a beginner like me? Or should i stick with something safer for a couple more projects? I can always try to build an EWI or something...   ;)

mirith


thanks guys.

well, the fog machine sounds like an idea that would work. But i think it is very unpractical.
Maybe it is better stop dreaming about seeing those "strings" and thinking about something that will actually work well!  ;)

What about "non-visible-string-harps", what would be a good idea?
What kind of sensors would be good?

I am afraid that those light sensors will work differently for instance while playing in a park outside on a sunny day and playing inside in a dark concert room.
Any ideas?


Yes, light sensors will probably work different in different light settings, but you may be able to minimize the effect by having a narrow wavelength and a calibration factor that you do on boot-up.  Unless I'm missing my guess on the idea, I personally am imagining a set of lasers pointed towards light sensors that you "pluck" by interrupting the gate, and reads it as an analog value that indicates how 'hard' you plucked the string.  While they would be mostly invisible (except as you pluck them), as long as the fog isn't too thick, you could still maybe use the fog machine idea.  I imagine Laser pointers would be good enough if you can find an appropriate light sensor for them (Just something to match the wavelengths).  Maybe shield the detectors a bit by covering them with an optical filter that passes the wavelength of the laser (Not sure the cost of this).

mrburnette

[quoteimagining a set of lasers pointed towards light sensors that you "pluck" by interrupting the gate, and reads it as an analog value that indicates how 'hard' you plucked the string.  While they would be mostly invisible (except as you pluck them), as long as the fog isn't too thick, you could still maybe use the fog machine idea.  I imagine Laser pointers would be good enough if you can find an appropriate light sensor for them (Just something to match the wavelengths). ][/quote]

My experience is that you will not achieve an analog change indicating 'how hard you plucked' the virtual string.  If the beam is aligned with the detector, the shadowing effect will essentially be On-Off, or full analog swing... I imagine that partial blockage would require millimeter precision of the shadow cast by the fingers - perhaps do-able with physical strings but my guess is that virtual strings would afford great difficulty.

But, you could build a 1-string experiment and make decisions.

Ray

boguz

I think i will try that.
I'm not too worried with the velocity ("or "how hard we pluck it"), but i do agree that that would be maybe hard to achieve with this kind of setup. I think a on/off kind of thing would be much easier.

I also read about a couple of Laser Harp Arduino Shields.
like this one: http://www.stephenhobley.com/blog/2009/03/19/arduino-shield-for-laser-harp-20/
or this one: http://lharp.weebly.com/index.html

There is also a nice tutorial about building one:
http://www.instructables.com/id/Laser-Harp/

At the moment, now that i start seeing things better, i think the biggest obstacle for this project will be budget.
If i build a laser harp, i would like to build it with, at least, 8 string. I can see the price of the component add up very quicly to several hundred dollars...
Maybe i have to start thinking about something else...   :S

mirith

Lasers are cheap:
http://www.seeedstudio.com/depot/5mw-laser-module-emitter-red-point-p-72.html?cPath=81_86

I imagine you can do even better if you can find an even more disassembled module, or hack something yourself.

Biggest cost will be your mechanical structure (in my mind) if you don't already have something.

Still I'd guess it could cost up to a total of $200 assuming your time is free.

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