Introduction: Frameless Laser Harp

About: Pushan Panda is a creative technologist and design educator. He has extensive experience in digital fabrication and industrial design. He is passionate about using design for positive social impact through pro…
We are a generation that love sound and light – can’t do without them really. Our most preferred time of day is night, or what we would call evening. We are particularly well acquainted with technology; doesn’t hurt these days. Our prerequisite for everything is that it be ‘cool’. Put it all together and in a stroke of brilliance, and a little help from our friend the internet, we have the ideal solution – a laser harp.

A laser harp, what on earth is that? Sounds kind of fancy doesn’t it? Well, it is basically what it says it is. The laser harp is an electronic instrument where a motor, a light sensor, a microprocessor Arduino, and, I’m sure you’ve guessed, a laser collaborate to produce beams, each representing a note (we will elaborate for those who care to read on). This harp though doesn’t have a frame: its strings stretch out infinitely into space – we know no boundaries.

Our inspiration was a video we had watched online and found rather fascinating. Apart from the fact that the prospect of creating it without too much expenditure, mental or monetary, was exciting, it seemed a project providing scope for learning in different areas, especially since we wanted to present it as a complete product. Part research, part reverse engineering led us to figure out its functioning. Admittedly, we have not contributed any addition to the original creation, but to achieve it was in itself gratifying. And there’s always room for originality and improvement in the future. 

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For making this laser harp you will require basic soldering skills, and some experience working with the arduino.

Word of caution: Lasers are very harmful for the eyes, make sure you wear appropriate eye protection.

Our Video will be ready in another 12 hours! Do come back and check it out!

Here's the link to the video that inspired us :

Step 1: Overview of the Harp

The basic outline of the harp:
A laser beam is shone. A stepper motor with a mirror divides it into nine beams. When one or more of the beams are cut, the light sensor (Light Detecting Resistor, LDR) detects it. According to the corresponding motor positions, it sends signals to the Arduino, which in turn produces the respective notes through a computer or keyboard.

How the beam is created:
A mirror is attached to the motor. The laser beam is directed to the mirror. The motor rotates in steps, hence stepper motor. With every step the motor takes, the position of the mirror changes, deflecting the beam in a different direction every time. The steps take place fast enough for the beams to appear as if they are simultaneously present.

How the harp knows which beam has been cut:
Every beam has a corresponding motor position. When a beam is cut, it reflects onto the sensor, which detects an increase in light intensity. The light sensor then looks for the position of the motor at the instant the beam was cut, and thus identifies the beam in question.

Step 2: Parts..

Here you will find the complete parts list you need and some info to create the project yourself:

Main parts
Stepper motor:
            A stepper motor is an electromagnetic device which converts electrical pulses into extremely 
            small mechanical movements (steps). Its shaft rotates by taking these steps when the 
            electrical command pulses are applied in the required order, and its speed and direction 
            depend on their frequency and sequence.
            A stepper motor has the following attributes:
                 •Number of steps per rotation
                 •Torque (the weight it can bear)
                 •Step angle accuracy
            By manipulating the control pulses, you can make the stepper motor carry out different 
            function such as taking half steps (e.g. 400/rotation instead of 200).
            For our project we will be operating in full step mode.

            Arduino is basically a small computer which reads an input, interprets it, and sends an output, where the input,output, and interpretation can be practically anything (in the electronic field!).
It is a magical board which makes your electronic dreams come alive.

Bread board:
Because the solderless breadboard for electronics does not require soldering, it is reusable. This makes it easy to use for creating temporary prototypes and experimenting with circuit design.
The more powerful your laser, the more effective your harp will be, ours was rated at:  <50 mW
        And as for color, we've chosen green, since it was completely safe for the skin at that power rating.

Rest of the parts and tools that you will need:
    Resistor 220 ohms 1/4W
    LDR Light Sensor
    MIDI jack
    MIDI to usb adapter.               (This parts is optional, it has been explained in the MIDI section)
    5k TRIMPOT
    Small Mirror
    Green Laser Safety Goggles
    White Gloves
    Power Supply, 12V DC  2A   (This parts depends completely on your stepper motor, go by its rated power)
    Soldering iron
    Materials for the enclosure

Total estimated cost:  90 - 100 $

Step 3: Wiring Guide for Steppers

It is essential to send the command pulses in the right order. A step motor will 
typically have six wires. Here is a quick guide to identify which is which.
With the help of a multimeter, we first isolate two groups of three wires, forming 
two coils, by checking the continuity function, ensuring that the circuit 
is complete. 

Next we identify the middle wire of each coil. Using the resistivity function, check
 the resistance between all combinations of pairs of wires. The resistance between
 two ends will be twice that between the middle wire and either end.

If your stepper motor does not have 6 wires, here is a wonderful resource to help you out:

Step 4: Wiring It All Together:

In the first image you will see the fritzing diagram for the harp. And in the following images you will see the step by step process for building the circuit on your breadboard.

We begin by placing the ULN2003, keeping in mind the direction of the little notch on the chip.
We then wire the stepper motor's signal pins into the chips OUT pins and the common wire into the chip COM pin.
In this step we connect to the arduino via the chips IN pins and we connect our power supply to the chip.
For the next steps we add the transistor, the laser, the LDR and the MIDI jack.
Refer to the fritzing diagram (first image)  if anything is unclear.

Your circuit is now ready!

Step 5: Arduino Code:

Copy and paste the Arduino code below into a new sketch,If you don't know how to create/upload a sketch, check out the official Arduino - Getting Started page. If you want to learn more about a specific command, just Google it.

We were having trouble embedding the Arduino code, so please click here for the code.
Or download the arduino files directly from this step.
We have put comments all along the way to make it easier for you to understand the code.
This is not the most efficient code, but it works. 

Step 6: MIDI Interface

Ok! So we are finally ready to make some music!

There are two options that you can take:
Option 1:
  Plug your harp directly into a MIDI keyboard and you are good to go.
  But if you want more control then go for Option 2.

Option 2: 
For this option you need a MIDI to USB converter, like in the first picture.
This works with any software that deals with MIDI, Here we show you how to go about it using FL Studio:

3rd Picture: First open FL Studio up, then click the OPTIONS button on the upper left corner and navigate to the MIDI settings. then select your MIDI device.

4th picture: The next step reveals the magic of MIDI, Right click on one of the tabs, in the Insert tab you will see a whole bunch of different sounds available to you, ranging from the classic sounds to the most modern sounding synths. Feel free to experiment with these sounds until you find your favourite one.  

Step 7: Layout and Enclosure

After some sketching we were quite satisfied with this diamond form for our harp.
For this step we encourage you all to come up with your own personalised enclosures.
We will simply walk you through our design process:
     We began with some simple brainstorming, and then we sketched out a few forms.
     Once we were satisfied with a form, we modeled it on Cinema4d to scale, 
     By modeling everything to scale we could do accurate dimensioning so that all our parts fit snugly into the enclosure.
     Since time was not on our side we could not make the enclosure out of wood, and so we decided to make a paper model        of it. 
The layout for the components we chose is depicted in the second picture, the motor and the laser are seperated from the arduino and the bread board by a small wooden platform.

Step 8: Conclusion

What we learned:

 Persistence of vision – this is what enables us to see the beams all at once,
 since the refreshment rate of the human eye is smaller than the rotation rate of
 the motor. 

How a stepper motor and Arduino work – we have elaborated on these in the
dedicated sections.

Physical programming – people are often under the impression that
programming is contained within the computer, but here we looked at a 
practical aspect of it where it controls physical actions.

The design process – steps from ideation to creation for a 
complete product.
Concluding thoughts:
Of course we made mistakes. Research is of paramount importance, especially when purchasing your parts – Google is your friend. But other than learning from our mistakes, we also learned to work as a team, by using each one’s plus points, and guiding those in unfamiliar territory when in one’s own comfort zone. We definitely could have 
done a better job with time management and organisation (which seem to be persisting problems with us), and in keeping up levels of energy and enthusiasm (which went through more downs than ups). Owing to our age and temperament, we underestimated the project and overestimated our capacity. We could not therefore accomplish the project as we had intended to. We would have very much liked to customise the harp by turning 
it into a complete package, giving it a name and logo. We also wanted to add elements to further enhance it -- controlling the volume and pitch according to the height at which you cut the beam, having the facility to sustain a note without holding your hand on it (pedal),  using a RGB laser to have changing colours
 according to the mood of the music, having the beams converge and diverge, and other visual effects. They remain prospects for our next edition.
Microcontroller Contest

Second Prize in the
Microcontroller Contest