The Prism a Laser Synth Guitar

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The Prism: A Laser Synth-Guitar
by jeff-o on June 30, 2009

Table of Contents
The Prism: A Laser Synth-Guitar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Intro: The Prism: A Laser Synth-Guitar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2

Step 1: How It Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

Step 2: The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

File Downloads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Step 3: The PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Step 4: Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Step 5: Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Step 6: Build the PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Step 7: Wire up the External Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Step 8: Wire Up the Power Jack and Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Step 9: Initial Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Step 10: Modify Your Guitar - Refinishing Part 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Step 11: Modify Your Guitar - Cutting Big Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Step 12: Modify Your Guitar - Refinishing Part 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Step 13: Build the Sensor and Laser Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Step 14: Mount the Sensor Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Step 15: Make the Pick Guard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Step 16: Final Assembly! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Step 17: Play It! Tune it! Play it Some More! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Step 18: Video and Audio Samples! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Step 19: Future Fixes and Revisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Step 20: Special Thanks, and Resource Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Related Instructables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Author:jeff-o
By day, Jeff is an electronics technologist at a large aeronautics corporation. By night, a mad scientist / hacker / artist / industrial designer wannabe!

Intro: The Prism: A Laser Synth-Guitar
The Prism is, quite simply, the best laser guitar on the Internet. At least I think so. I hope that you take these instructions and not only make your own, but improve on my
design!
I suppose I should clarify what the Prism is: It's a bit like a guitar with some synthesizer mashed in. It has aspects of a theremin and a laser harp thrown in to boot. In
short, it's not like anything else, and you can use it to make some really neat sounds. Anything from cold Sine and harsh square waves to heavily distorted noise.
At its heart the Prism features a VCO (Voltage Controlled Oscillator), based around the very shiny XR2206 monolithic function generator. The octave range is selected by
blocking one of four laser "strings," and the pitch is controlled by the position of the musician's hand on the fretboard. The musician has the option of selecting a sine,
triangle or square wave. The sine and triangle waves can be skewed using a separate Skew control.
It also has two other controllable oscillators, one acting as an LFO (Low Frequency Oscillator) and the other acting as a Sync generator.
I designed the Prism to plug into any regular guitar amp, with no computer required. In fact, there is no programming involved at all in this project! It is just as portable as
a regular guitar, and meant to be used at gigs or wherever else an "alternative" instrument is needed!
Here is a video showing the basic functions:

And here I demonstrate the on-board effects:

Visit the Sample page to hear me "jam!"

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Step 1: How It Works
I searched the Internet for days looking for the perfect solution. At first I considered making the Prism a MIDI device, controlled by an Arduino (like the Laser Harp seen in
MAKE Magazine). Ultimately, I decided to make it completely standalone, like a normal electric guitar, requiring a minimum of external equipment and compatible with
everything.
That led me to research various (all-analog) oscillator possibilities. This time simplicity was key, since it all had to fit inside the body of the guitar. There are a number of
single-chip voltage controlled oscillators out there, but the only one that is actually in production is the XR2206. This neat little device takes a control current or voltage
and produces either a sine, triangle or square waveform that is proportional to that control. The control can be as simple as a potentiometer, or something more complex
like the infrared range finder I used. During my search I happened upon a most excellent design by Thomas Henry. It had everything I needed to get started.
The Prism is based on Thomas' design, with a few modifications. I removed some of the control inputs, such as the exponential FM and voltage-controlled Skew. I then
added my own custom-designed laser-controlled capacitor bank, a hard-wired LFO generator (based on an XR2206 reference design from the datasheet) and a hardwired "sync" circuit based on a 555 timer. Oh, and a Sharp Infrared rangefinder to control the pitch.
So how does it work?
Well, I mentioned before that the output frequency is controlled by an input voltage. The three input control voltages, Coarse (the range finder), Fine (a trimpot on the
board), and LFO are all mixed together and converted to a current (taking the place of a potentiometer). This current, along with a capacitor from the capacitor bank,
determines the frequency produced by the XR2206.
Normally you'd only use a single fixed capacitor, but I wanted each laser "string" to select a different frequency range. The Prism accomplishes this by having each laser
trigger a phototransistor, which in turn controls a comparator. If the laser is blocked, the phototransistor turns off and the comparator goes low. This causes a solid state
relay to turn on, connecting its corresponding capacitor to the XR2206's capacitor input. When no lasers are blocked, no capacitors are connected and the oscillator
produces a frequency above the audible range.
To control the pitch, I used a Sharp infrared rangefinder. You've probably seen this used on autonomous robots, and perhaps some theremin-type instruments. This neat
little device measures objects between 10 and 80 cm away, and generates a corresponding analog output between 2.4V and 400mV, respectively. This voltage swing is
quadrupled with a simple op-amp on the board.
The desired output waveform is selected by turning a rotary switch, that selects between the sin/tri output and the square output. The frequency and amplitude is the
same no matter which waveform is selected.
The skew knob causes the triangle and Sine waves to skew - that is, they get chopped up and lean to one side or the other. For instance, the triangle wave can be made
into a ramp for a slightly different sound. The effect is even more pronounced with the sine wave, which goes from a nice clean sound to very harsh and metallic.
The LFO effect can be varied by turning a knob, and turned off by pushing the knob (a very clever design, if I do say so myself!) Its effect can be varied from a slow rise
and fall, to a nice vibrato, to a high pitched trill sound.
The Sync only affects the Sine and Tri waves. It is also controlled by a rotary knob, and can be switched off. Each time it transitions it causes the main VCO to reset,
chopping up the sound in interesting ways.

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

There are also a few more on-board trimpots, used for tuning the output waveform. These are only touched once when the Prism is first constructed.
The Prism can be plugged into any regular guitar amp, or it can be modified to control a separate synthesizer setup.
A separate power supply is also needed, that produces +15, -15 and +5V. The lasers are driven by a 3V regulator that "spoofs" the voltage the lasers are expecting.

Image Notes
1. This is how the board looked after all the modifications I did to it. The final
version of the board has no cris-crossing wires!

Image Notes
1. Mods

Step 2: The Circuit
Everything is contained on a single 3x5" double-sided circuit board. I designed the schematic and PCB in Cadsoft Eagle, but unfortunately the size is above the limits of
the free version. You can still view the files, but you can't edit them without at least the student/non-profit Standard edition.
Feel free to experiment with component values, but be aware that some of the values are rather specific, and changing them too much will adversely affect the operation
of the circuit, potentially causing damage to components on the board or to devices connected to it.
All of the "external" controls - the ones that are used by the musician on a regular basis - are connected to the board using header connectors. This is optional, but I do
recommend it since it makes troubleshooting and assembly easier (or possible, in some places!)
At first I was going to design my own power supply, but then I found a nifty pre-built power supply with exactly the specs I needed. It's a little pricey at $60 but I think it
was worth it. Who wants to mess about on something trivial like the power supply? The Prism was designed to run on +15, -15 and +5V, though it may work just fine on
+12, -12 and +5V, which means you could use a modified computer power supply. I haven't tried it though, but it certainly wouldn't harm the circuit.

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

File Downloads

laser guitar.brd (58 KB)
[NOTE: When saving, if you see .tmp as the file ext, rename it to 'laser guitar.brd']

laser guitar.sch (294 KB)
[NOTE: When saving, if you see .tmp as the file ext, rename it to 'laser guitar.sch']

PrismPartsList (9 KB)
[NOTE: When saving, if you see .tmp as the file ext, rename it to 'PrismPartsList']

Step 3: The PCB
I made the circuit board using the toner-transfer method. It's my new favourite method of making boards! It's faster than the photo-resist method, and it's easier to
produce good results. Oh, it's also cheaper and doesn't produce as many waste chemicals.
I won't go through the whole process here, there are plenty of guides online. But, I'll go over the basics.
Start by printing out the PCB artwork. The toner transfer method requires you to print using a laser printer on glossy photo paper - use the smoothest, shiniest stuff you
can get. The bottom artwork should be printed normally, and the top artwork should be a mirror image.
Cut a piece of plain double-sided copper clad board slightly larger than the artwork, and place either the top or bottom artwork with the printed side towards the copper.
Be sure the copper is clean to ensure a good transfer. You may tape the artwork to the copper clad using heat-resistant tape, to prevent it from sliding around. Now, place
the board on an ironing board with the artwork on top, and lay a piece of plain paper on top. Some photo paper contains plastic that will melt onto the iron - the plain
paper prevents this.
Now, with the iron on the hottest setting (and no steam!) , press down on the board for a few minutes. It's not necessary to move the iron unless the board is bigger than
the iron.
After a few minutes, remove the iron and place a heavy, heat-resistant object like a cooking pot or glass baking dish on top of the board. This will keep the paper pressed
against the board while the toner cools.
When the toner and board are cool, peel off the photo paper. If you're lucky and are using photo paper like I have, it will peel right off leaving the toner securely adhered
to the copper. Some photo papers may require you to lightly scrub off the paper under running water.
Now, note the four mounting holes in the corners. Drill a 1/32" pilot hole in three of them. Take note of which holes these align with on the second piece of artwork, and
punch a small hole in these locations on the artwork with a pin. When you line up the second piece of artwork on the copper clad board, make sure these holes line up
PERFECTLY.
To prevent the toner that's already transferred from sticking to anything, lay a plain piece of paper on the ironing board, then a piece of unprinted photo paper, then the
board and remaining artwork. Apply heat with the iron as before.
When both sides are transferred, inspect the board carefully for any toner that didn't transfer, and for any other damage. Repair the damage using a black fine-tip Sharpie
marker.
Etch the board in either Ferric Chloride or Ammonium Persulfate according to the directions on the bottle. Inspect the board regularly to make sure that the toner and any
repairs are not being etched away. When the etching is complete, thoroughly wash and dry the board with a lint-free towel. The toner and Sharpie marker are easily
removed using nail polish remover and a cotton ball.
The last step is to drill the holes. I used a 1/32" bit in my drill press. This step seems to take forever, but be patient and be sure to drill in the exact centers of the holes.
I may order a bunch of professionally-made boards from a boardhouse, at a cost of about $12 each plus shipping. If you're interested in a group buy, let me know!
*

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Image Notes
1. Glossy inkjet photo paper
2. Save paper - print the top and bottom on one sheet!

Image Notes
1. Taped to the copper clad board using heat-proof Kapton tape.

Image Notes
1. A sheet of plain white paper prevents the plastic in the photo paper from
melting to the iron.

Image Notes
1. Apply even pressure for 3-5 minutes.

Image Notes
1. I used a glass baking dish to apply weight to the transfer while it cools.

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Image Notes
1. Damaged traces that need to be repaired. This could be the result of
insufficient toner on the paper, from an air bubble, or from dirt on the copper.

Image Notes
1. It's hard to see, but you can repair traces using a few coats of permanent
marker.

Image Notes
1. Once one side has toner transferred, drill an alignment hole at the exact
center of the mounting holes.

Image Notes
1. Punch the exact center of the alignment hole with a pin, and use that hole to
align the second layer pattern with the board.

Image Notes
1. Align the punched holes on the paper with the drilled holes on the PCB.
Perfect alignment is critical!

Image Notes
1. Ooo pretty! Ammonium Persulfate is much nicer than ferric chloride.

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Image Notes
1. Clean off the toner using nail polish remover (or just plain acetone).

Image Notes
1. Most of the holes were drilled with a 1/32" bit in a drill press. The headers
may need one size larger, like 3/64."

Image Notes
1. All drilled and ready to be soldered!

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Step 4: Parts List
Did I mention how many parts are needed? A lot. And no, I'm not interested in making up kits - I just don't have the time! All the electronics can be obtained from three
sources: Digikey, Mouser, and DealExtreme. Apologies to you folks living outside of North America, you're on your own...
UNIQUE ITEMS:
A donor guitar - should be solid core, either a regular electric or electric bass.
A few scraps of wood - for building the sensor and laser blocks
Spray paint, in your choice of colours (only necessary if you strip and refinish the guitar)
Something to make a pick guard from (if your guitar doesn't have one that can be used or re-used)
A case of some sort for the power supply (project box or something custom-made)
DealExtreme:
Four 10 mW green laser pointers (if you live in the States, get 5mW lasers because 10mW is apparently illegal) In hindsight, a red laser would probably work just was
well, but it just doesn't have that "cool factor..."
Mouser and Digikey:
Everything else comes from here. I used all metal film resistors for better tolerances (and in some cases, to get just the right value). Use ceramic and aluminum
electrolytic capacitors for the power supply bypass capacitors, and higher quality polypro caps for the audio-signal capacitors. Any of the specialty components, such as
the phototransistors, relays and ICs are marked on the schematic.

Image Notes
1. The Victim.

Image Notes
1. Rotary switch
2. Fancy pant potentiometer
3. Shiny potentiometer-switch combo
4. Sharp IR Range Sensor
5. 4-pin DIN-style connector
6. Standard 1/4" phono jack

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Step 5: Tools
Oh yeah, you also need quite a few tools.
For the Electronics:
- A soldering iron with a fine tip
- wire strippers
- wire cutters
- tweezers
- needle-nose pliers
- a drill press
- a heat gun (for heat shrink tubing)
- solder
For Guitar modification:
- A drill press
- A hand drill
- assorted drill bits, including Forstner bits and countersink bit
- A router with a 1/2" flat-bottom bit
- a scroll saw, table saw or band saw
- a screwdriver
- tools for refinishing a guitar (scrapers, sandpaper, palm sander, respirator)
For Testing and Calibration:
- A multimeter
- an oscilloscope (not absolutely necessary, but very, very, very helpful)
- headphones or a guitar amp
- mono patch cable (if using a guitar amp)

Step 6: Build the PCB
So, have your boxes from Mouser and Digikey arrived, packed with goodies? Yeah, they cost you a bit but it'll be worth it.
Print out the component layout and parts list and set them out in front of you. The parts list will tell you what part in that big box corresponds to each designation, and the
component layout will tell you where to put it.
I tried very hard to make as few top-side solder joints as possible. If you are using a pro-manufactured board this isn't an issue, but if you made your own board some of
those joints will be tricky. You can place components in whatever order you wish, but in general it will be easier to install the potentiometers first, then work from smallest
to largest where possible. For each component make sure you solder both top side and bottom side connections, since some traces rely on this top-to-bottom connection
for continuity.
Also make sure that every component is installed in the right direction. The component layout drawing will show you how polarized components (like the big capacitors,
ICs and diodes) are meant to be installed.
There are a few pads and traces that are very close together. Again, I tried to minimize traces passing between pins, but I couldn't eliminate all of them. This isn't as
much of a problem on pro boards, but be sure that you don't make any solder bridges. Shorts like this can be harmless, or they can make stuff blow up. Be careful.
Finally, a note on the tiny temperature compensated resistor. Thomas' original design used an ordinary through-hole component, but I was unable to get one in a
reasonable amount of time. By all means, if you can get a 2kohm 3500ppm through-hole tempco resistor, use it! Otherwise you'll have to rig up a surface mount part like I
did.
When everything is soldered in place, inspect your work for mistakes and soldering errors. Now inspect again. And again.
***Please note that your board won't look exactly like my pictures. The pictures below are of the "alpha" PCB, which has since undergone heavy modification. The files I
provided are all up-to-date.***

Image Notes
1. Parts layout
2. A big, scary parts list
3. Hours of work ahead...

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Image Notes
1. Potentiometers first. It's just easier, especially for the ones that need top-side
solder.

Image Notes
1. An example of top-side solder on a connector. You can solder the bottom first,
then slide the plastic up, and solder the top. When the solder is cool, slide the
plastic back down on top.

Image Notes
1. Top-side solder on an electrolytic capacitor. Use a fine-tip soldering iron.

Image Notes
1. I designed the board to use vertically-oriented resistors, to take up less space.

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Image Notes
1. If you have a choice, put the end with a longer lead through the hole that has
a top-side solder joint. It just makes things a bit easier.

Image Notes
1. All done, except for one part...

Image Notes
1. 3500ppm temperature compensation resistors. These keep the output stable
when the temperature increases.

Image Notes
1. Cut a tiny sliver of Kapton tape to attach the resistor to the IC.

Image Notes
1. Cut two scrap component leads and solder them between the mounting
holes and the resistor.

Step 7: Wire up the External Components
Each of the external controls connects to the PCB using a short piece of wire, terminated with a female header connector. Unfortunately, the tiny pins that crimp onto the
wires require a special tool, one that is expensive and hard to get. Fortunately, you can get close enough by painstakingly crimping them by hand with needle-nose pliers.
For wire I used a bunch of stuff that I fished out of the trash at work. It was perfectly good wire, just too short for most applications. You may not be so lucky and will have
to buy wire. Get lots of colours to make assembly easier later on.
Start with the audio jack, it's the easiest. Measure out a length of wire that will easily reach from the eventual mounting position, to where the connector is when the board
is mounted in the guitar. Solder the wires onto the terminals on the audio jack, and slide heat-shrink over the terminals for a neat finished look. On the other end, strip
about 3mm of insulation from the wire, and fold the tiny wings of the pin around the wire. If you've never done this before, you'll probably screw up. The wings will need to
be folded flat enough that the pin can be inserted into the connector. But don't insert the pin all the way! For extra security, drop a small amount of solder onto the
connection as well. Then, being mindful of which wire goes into which position (pin 1 is marked with an arrow), insert the pins into the connector.
The Skew potentiometer is the next easiest, with just three wires. Do these the same as the audio jack, and twist the wires together to keep them neat.
Next up are the LFO and Sync knobs. These are harder, and require a bit more planning. These knobs have both a potentiometer and a switch inside. Don't mix these
up! Use different coloured wires if you can, to help keep them separate. Make sure you solder to the correct pins for the switch, and also make sure the right wires go to
the right positions in the 5 pin connector.
The rangefinder connector is hard to do, since you have to crimp pins onto both ends. If you thought the regular pins were hard to do, wait till you try the miniature ones
on the sensor end! It's maybe a good thing that you have to buy a minimum quantity, since there's a good chance you'll destroy at least one pin in the process.
Alternatively, you can buy this sensor with a pre-made wire and save yourself the hassle.
Last up is the rotary switch. This one's hard. If you use the same switch as me, you'll first have to configure it for triple-throw. That is, three switch positions. This is done
by removing the lock nut and washers from the threaded section. There is a small washer inside with a pin that fits into one of 10 slots (2 to 11 positions) - place it in the
position that will give three positions (or two clicks). You'll see what I mean when you try it. Put all the washers back on, and then proceed to solder on the wires. There
are three "sectors" here, consisting of one pole and three positions. If you bundle the sectors into groups of four and maintain the same colour amongst the different
positions (ie. black for all the poles) then the resulting three connectors will be interchangeable. It's complicated, but you're smart. You'll figure it out.

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Image Notes
1. Rotary switch
2. Fancy pant potentiometer
3. Shiny potentiometer-switch combo
4. Sharp IR Range Sensor
5. 4-pin DIN-style connector
6. Standard 1/4" phono jack

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Image Notes
1. A crude layout to help determine cable length.

Image Notes
1. Make sure you know which pin on the photo transistor is emitter and collector!

Image Notes
1. These are all interchangeable. The black wire goes to pin 1 on each of
them.

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Image Notes
1. These are a pain to crimp with pliers!

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Image Notes
1. Tricky, fiddly work.

Image Notes
1. Notice the wires switch.

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Image Notes
1. This green, yellow, red pattern is the same for all the pole positions, so that the
cables are interchangeable.

Step 8: Wire Up the Power Jack and Power Supply
I used standard 4-pin DIN connectors for the power. You could use any 4-pin connector you like, but I like these DIN connectors because they lock in place and are very
sturdy.
Anyway, these connectors are actually really easy to hook up. Both the plug and receptacle ends use solder cups - simply insert a short section of stripped wire, and feed
in some solder. For the two sockets, be mindful of the pin number (there are tiny numbers printed on the connectors), and maintain the same number and wire colour
throughout to keep yourself sane.
I would have preferred to use some nice stranded power cable for this, but all I had was 8-conductor ethernet cable. I grouped the wires in pairs (blue/blue,
orange/orange, etc.) and managed to fit two of these wires in each solder cup. I highly recommend using a shielded 4-conductor stranded cable for this, if you can. The
assembly of the connector itself is tricky, and the order of the various sleeves is critical. Do one end first so you know the order, then thread the sleeves on the other end
BEFORE soldering on the second connector. Fortunately the connector I chose is easily rebuildable so if you make a mistake it'll just cost you time, and not money...
As I mentioned earlier I used a pre-made +15, -15, +5V power supply. This cut out a lot of development time for me, and the end result was a supply that is smaller and
lighter than anything I could have made. It's almost small enough to fit in the guitar itself! I desoldered the existing connectors and hard-wired an AC jack to one end, and
the power jack to the other. You will also need to do one modification to the power supply: solder a single wire between the +5V ground and the +15V/-15V ground, so the
two grounds are at the same potential. You may craft a custom enclosure for the power supply, or just stuff it into a project box.

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Image Notes
1. A +15, -15, +5 Volt power supply

Image Notes
1. I didn't know which connector was compatible with this receptacle, so I
desoldered it and hard-wired my own connector.

Image Notes
1. I also removed the power-in connector.

Image Notes
1. A power jack, stolen from an old printer.

Image Notes
1. Make sure the wires go to the right hole!

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Image Notes
1. This wire connected the two "grounds" so they are at the same level.

Image Notes
1. I used ethernet cable - use a proper 4-conductor shielded cable if you can.

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Image Notes
1. The various bits and pieces should be in this order before you solder on the
connector.

Image Notes
1. The two end plates are marked for holes.

Image Notes
1. I cut out these holes on my scroll saw using a metal-cutting blade.

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Image Notes
1. As clean as can be!

Image Notes
1. The completed power supply!

Step 9: Initial Testing
Oh, fun! With everything wired up you can actually test the circuit.
The first thing to do is to measure the power supply rails for shorts. With a multimeter, measure all the combinations of +15V, -15V, +5V and Ground and be sure none of
them read zero ohms. Next, plug in your power supply without the Prism circuit board connected, and make sure you have the right voltages coming from the right pins.
All set? Ok, so far, so good...
Plug the following external controls into the board, making sure that pin 1 on the connector goes to pin 1 on the board: LFO control (with switch turned off), Sync control
(with switch turned off), rangefinder, and any three of the phototransistors. Don't hook up your amp or headphones yet - instead, connect an oscilloscope to the output, or
at the very least a multimeter set to DC voltage.
Power it up, and see what happens. Ideally, nothing special. If you see smoke, UNPLUG EVERYTHING! You made a mistake - go back and fix it (and replace whatever
part made the smoke). Ideally, there should be a waveform of some sort visible on the oscilloscope, most likely with a DC offset. If you're just using a multimeter, you may
just see a steady DC voltage. The first thing to do is to adjust the offset, this is done by turning trimpot R33. Adjust it so that the DC offset is as close to 0V as possible.
Note that the sine waveform controls (Rxx and Rxx) will mess up the offset to the point that you can't get it to 0V - if that's the case, adjust the sine shape trimpots at the
same time.
The rest of the calibration is virtually the same as described on this page. Follow those instructions and you should do fine. Note that movement around the range sensor
will cause the frequency to change (as it should) - if this makes the circuit too hard to tune, then plug the skew control potentiometer into the range finder's input, and set
it to about mid-level. It will remain stable while you're tuning.
If you have a scope, you can also test the function of the LFO and Sync generators. Probe the LFO on pin 2 of the LFO XR2206, and pin 3 on the 555 timer. Adjusting
the controls should cause their output frequencies to change accordingly.
Hopefully, everything will work out the first time. I spent countless late nights working out the bugs in my design so it should work fine for you. If something isn't working,
I've found the top causes to be:
1. Solder shorts
2. unsoldered pins
3. backwards and incorrect parts
4. debris or bits of wire on the board
5. bad connector/wire connections
If you have a scope, it's pretty easy to trace the route a signal takes, and note where it stops (or gets messed up or whatever). With just a multimeter you can still do
some testing, such as making sure the chips are getting power, and checking DC voltage levels where appropriate.

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Image Notes
1. A somewhat dangerous thing to do: 120V within easy reach!
2. The board is ready for testing and calibration!

Step 10: Modify Your Guitar - Refinishing Part 1
Make absolutely sure that the guitar you're devoting to this project is one or more of the following:
- unusable as a regular guitar
- a cheap knockoff that you don't mind hacking to pieces
- not worth restoring as a regular guitar
- one of many guitars you've got lying around and you don't mind hacking up
Well, you get the idea. Once converted to a Prism Laser Guitar, it can never go back.
Start by removing all the hardware from the guitar - strings, pickups, jacks, knobs, pick guard (if there is one), etc. Strip it down until all that's left is wood and paint. But,
do save the pieces because some of them may be reused (or at leased used as a reference).
The old bass I'm using appears to be a Gibson Explorer clone (a garage sale score, graciously donated by my best pal for this project). It was in pretty rough shape, with
paint worn to the wood in some places and a lot of nicks on the fretboard. I decided to refinish it.
I started by removing the neck of the guitar. This wasn't an easy task - the previous owner (not my friend) glued it down with epoxy. I literally had to snap it off across my
knee like a piece of kindling. Thank goodness the epoxy bond broke and not the neck! I chipped off the old epoxy with a chisel.
I then scraped off the old paint. This was far easier than I had anticipated - it literally flaked off in big chunks using nothing more than a sharp 1" wide chisel. No wonder it
was worn so badly! All that was left was a layer of primer, which easily sanded off using an oscillating palm sander. If you use a palm sander for this task, wear breathing
and eye protection because the paint dust gets everywhere! Do this outside as well, if you can.
Since the laser guitar has no strings, I filled in the holes where they used to pass on the back of the guitar by gluing in 3/8" dowels and planing them down to the same
level as the body. I filled other holes, like those left by the thumb rest, with carpenter's putty and sanded them smooth.
I guess this was a fretless bass, since all it had were grooves cut into the fretboard, rather than raised metal frets. I decided to make it REALLY fretless, and filled in those
grooves with putty as well. I sanded the fretboard as smooth as I could manage.

Image Notes
1. Remove the neck for refinishing.

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Image Notes
1. I was lucky and the original pain came off in big flakes.

Image Notes
1. All that's left is some thin primer.

Image Notes
1. Originally, the strings passed through the guitar and attached on the
underside. I filled the holes with wood dowels.

Image Notes
1. The primer came off easily with a palm sander. This photo is a fake - I did all
the work in my garage with a respirator on!

Image Notes
1. It cleaned up really well!

Image Notes
1. The palm sander could reach this section, I did it by hand.

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Image Notes
1. The holes and cracks are filled with wood filler.

Image Notes
1. I'm not sure if the frets were removed by accident or on purpose. I filled them
with wood filler too.

Step 11: Modify Your Guitar - Cutting Big Holes
The PCB will need a place to go, and that means cutting out a big 3x5" cavity right in the middle of the body. After doing this, there really is no turning back!
Using the PCB as a reference, locate a suitable position somewhere on the body. Try to use as much of the space taken up by the pickups as possible, to minimize the
amount of cutting you have to do. Mark out the space with a pencil. I was fortunate, there was enough space where the old knobs were to mount the four new ones.
When choosing a location for the board, also ensure that you can eventually cover it with a pick guard of some sort, to protect the electronics. Also make sure you leave
room for the sensor block and laser block.
Drill out the majority of the wood using a 2" Forstner drill bit. It's easier and faster than using a router for everything. Drill to a depth of 0.75-1" depending on how much
space you need for your PCB. There should be enough room to plug in the connectors, but no more. With the majority of the wood removed, finish the edges using a
router with a 1/2" straight bit. Also cut channels to where the laser holder, sensor block and (if necessary) the control knobs will go. These channels don't have to be as
deep as for the PCB itself; just enough for the wires.

Image Notes
1. The location of the PCB is marked out.

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Image Notes
1. One big drill bit! This is a 2" Forstner bit.

Image Notes
1. The damage is done. There's no turning back now!

Image Notes
1. A rough cavity is cut with the drill press.

Image Notes
1. Use a router to finish cutting the cavity.

Image Notes
1. Tape used to help with routering, to better see the edge.

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Step 12: Modify Your Guitar - Refinishing Part 2
With fresh holes cut into the guitar's body, you can repaint it however you wish (assuming you stripped off the old paint).
I chose a dark blue and black colour scheme for my guitar, with a bit of sparkle. I used spray paint for everything. I started with a coat of dark blue on the body, enough to
hide the repair work and the stripes of the wood veneer. I then dusted the body with Duplicolor Metal Flakes paint - enough to give a bit of sparkle, but not enough to
obscure the dark blue base coat. I then finished the body using Duplicolor Acrylic Enamel.
I spray painted the neck of the guitar jet black. This was done for a few reasons - first, because it looks cool. Second, to hide the repairs done to the chipped frets. Third,
because it would help the performance of the range sensor (ok, that's probably the most important reason!) The neck was also finished with acrylic enamel.
When repainting your guitar, make sure the various spray paints you use are compatible with each other. Do a test on a piece of scrap wood. You definitely do not want
the solvent from the clear coat dissolving a layer underneath!!

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Step 13: Build the Sensor and Laser Blocks
Custom holders need to be built, onto which the sensors and lasers are mounted. There are two blocks needed, one to hold the range finder and phototransistors, and
one to hold the laser pointers.
I started by measuring the distances between the strings, and the distance between the strings and the body of the guitar when they were still mounted. I found that the
strings were just under 2cm apart, and about 1.6mm off the body. I rounded off those numbers to 2cm apart, and about 1.8cm off the body.
The sensors are mounted inside 1/4" brass tubing, which happens to have the perfect inside diameter to fit a 5mm LED-style phototransistor body. The tubing helps
prevent stray light from reaching the phototransistor, which is important because it is sensitive to the same wavelengths as the human eye. I had to use this type of
phototransistor because I used green lasers - typical phototransistors are not sensitive in the 550nm range which is what the green lasers produce.
I drew 1:1 scale patterns on graph paper to plan out how the blocks should be built. On them I indicated the basic dimensions and where the holes should be drilled.
The blocks themselves are made of two layers of Baltic Birch plywood (something I have on hand all the time these days!), one 1/2" and one 3/4". I glued them together
with carpenter's glue, then pasted the patterns directly onto the wood.
The sensor block consists of four 1/4" holes on one side, into which the brass tubes are fitted. The fit is tight enough that no glue is needed. The side of this block and the
tubes themselves are cut off at a 45 degree angle, purely for aesthetic reasons. The other side of the block is flat, and provides a place for the range sensor to be
mounted. A single hole is drilled below the range sensor for the wires to pass through.
On the underside of the sensor block, I drilled holes that would meet up with the brass tubes. The phototransistors are inserted after the tubes are installed, and held in
place with a dab of hot glue. I stuffed some black electrician's tape in around each phototransistor, to prevent light from leaking from one sensor to the other. Two
counter-sunk screw holes are drilled at opposite ends for mounting the block to the guitar.
The laser block is built in a similar way, with the laser pointers spaced to match the brass tubes (2cm apart). This block was a little harder to make. The problem is the
switches on the lasers - I was unable to get at the "guts" of the laser pointers, so I had to build the block to both hold the body of the laser pointer and push the button at
the same time. I did this by first drilling a smaller hole along which the button would slide, then a larger hole for the body of the laser. The pointer slides in place and if
you're lucky, the button is pushed down due to tight tolerances. This only happened for two of my lasers, so I had to add screws to push them down permanently. Drill
one 9/64" access hole for each button in the bottom of the block (measure carefully!) and screw in 8-32x1/4" set screws to "push" the buttons. Finally, drill three
countersunk holes for the mounting screws. Make sure you don't drill holes where the lasers or wires will be!
As I mentioned before, I was unable to open the lasers without damaging them. Instead, I unscrewed the barrel holding the batteries and soldered wires directly to the
terminals. Well, that's half true. I soldered the negative wire to the spring in the center, and used conductive silver epoxy to glue the positive wire to the case. I wish there
were a less expensive way to do this! (Please let me know if you think of one.) I terminated the wires in connectors, in the same way as the sensors and controls
described earlier. The lasers were a tight fit and I didn't need glue to hold them in, but by all means add a dab of epoxy or hot glue if you find that they don't stay in on
their own.

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Step 14: Mount the Sensor Blocks
The sensor blocks should be mounted before designing the pick guard, since the pick guard needs to be designed around the blocks. Alignment is critical, so take your
time and get it right the first time!
Start with the sensor block. It should be mounted so that the range finder is centered relative to the neck of the guitar, and so that the sensor is pointing straight down the
middle. I actually used a carpenter's square to make sure the sensor was perfectly aligned. Also remember that the minimum sensing distance of the range sensor is 10
cm - it should be placed a few centimeters from where the neck starts, so that the player's hand cannot get too close to the sensor. When you're satisfied with the
position, advance the screws so that they poke out just a bit. Push the block onto the body of the guitar, to make dents where the screws should be. Use the dents as
guides to pre-drill the holes, using a drill press.
Mounting the block can be tricky. Bundle up the cables so that they exit the bottom of the block in the same location - as close as possible to the channel cut into the
wood. If everything is lined up properly, the block should sit flat on the body of the guitar, and none of the wires pinched underneath. Screw down the block when it's lined
up.
Now, using the sensor block as a reference, mount the laser block in a similar way. The lasers should each point directly at a sensor tube. Use a ruler for alignment, or
even power up the lasers to get it perfect. As before, use the screws to make dents in the wood, then drill the holes. And, as with the sensor block, bundle up the wires
and make sure they travel down the cut channel to the main cavity.

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Step 15: Make the Pick Guard
This part is also tricky, and will be different for each guitar depending on its shape. The pick guard in this case is less used to protect the guitar from errant picks, and
more to protect and hide the electronics underneath! It can be made from whatever material you wish; metal, plastic, carbon fiber...
I studied the design of pick guards used on other Gibson Explorer guitars (and its many clones) and came up with something that I think is pretty close to the original,
while adding extra coverage for the electronics. It needed to extend between the sensor and laser blocks to hide the channels, and over to the controls as well. I suppose
this covers a lot of the shiny blue paint. If I make another guitar like this one, I'll try harder to cut channels under the surface of the wood, so that I can separate the
pieces.
This part was done almost entirely by hand. I traced the outline of the guitar body on a piece of paper, then drew a pattern for the pick guard freehand. I went through
three revisions of drawing a pattern, cutting it out, laying it on the guitar, and making note of adjustments to make. When I was satisfied with the design, I transferred it to
a sheet of 1.6mm thick aluminum sheet, and cut out the pattern on a band saw. I finished the rough edges and got the fit around the blocks perfect using a belt sander.
I used Illustrator to plan out the spacing of the control knobs. I printed out the pattern and laid it on top of the cavity where the controls would be, with tape facing stickyside up. When the pick guard was laid on top, the pattern transferred into the exact correct position on the underside of the pick guard. It was then an easy matter of
drilling out the holes for the controls on a drill press.

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Finish the pick guard by drilling screw holes all around the edge for mounting. I used flat-head #3 1/2" screws, so I countersunk the holes as well. You don't need that
many screws, maybe one in every corner and then every three or four inches.
You will also need to make a new mounting plate that holds the power cord and the 1/4" jack. This one's much easier to make; just measure the appropriate spacing for
the jacks and cut a plate to match.
Depending on what material you used to make the pick guard, you may want (or need) to polish it. I used increasingly fine grades of automotive sandpaper to polish the
aluminum. I also decided to etch the knob labels, a laser caution label and my signature onto the aluminum using electrolytic etching, as described in my Valvelitzer
Trifecta Instructable. This step is optional (and only possible if you use a metal pick guard!)

Image Notes
1. I traced the outline of the guitar onto a large sheet of graph paper.

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Step 16: Final Assembly!
At last, the time has come to put everything together in a playable package!
Start by mounting the Prism circuit board in its cavity using a screw in each corner. Plug in the sensors and the lasers, being sure to observe proper polarity.
Next, mount the 1/4" output jack and the power cord onto their plate, thread the wires through the hole, and screw the plate onto the side of the guitar. Plug in the cables
and flatten the wires down against the bottom of the cavity.
Mount the various controls in their positions on the pick guard (or on their own separate plate, if that's the case on your guitar). Tighten the nuts being careful not to
scratch the pick guard. Plug the cables into their respective positions, again being mindful of polarity. Route the cables into the cut channels, and lay the pick guard flat
against the body of the guitar. Screw it in place.
With the pick guard in place, attach the knobs onto the control shafts.

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Step 17: Play It! Tune it! Play it Some More!
Hopefully, the tuning you did in step 9 is still okay. Before plugging the guitar into power, again check to make sure nothing is shorted by testing with a multimeter. Before
plugging the guitar into an amplifier, measure the output with an oscilloscope (or in a pinch, a multimeter) to make sure there is no DC bias, and to make sure the output
is 1 Volt peak-to-peak.
If the output is happy, go ahead and plug the Prism into an amp and play around! I haven't played with mine nearly enough to have developed a technique, so feel free to
play yours in whatever way produces the best sounds. Play around with the knobs and experiment with the sounds it produces. Take some time to get used to "plucking"
laser strings that you can't feel, and can barely see. Note how your hand position on the neck influences the frequency in a non-linear way.
If anything doesn't sound quite right, you may have to open up the guitar and do some fine tuning of the internal potentiometers. Here is what the various potentiometers
do:
R34 changes how sensitive the range finder is - that is, through how many octaves the frequency changes from close to far range.
R40 is also used for tuning sensitivity, at higher frequencies.
R33 adjusts fine tuning - this can pull the overall output frequency range higher or lower. It also helps "squelch" noise produced by the range finder.

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R36 adjusts sine "roundness" - adjust this for a good sine curve
R39 adjusts sine and triangle wave symmetry (ie. how far they lean to one side) - adjust this for a centered waveform.
R35 adjusts sine and tri offset - aim for zero DC offset.
R38 adjusts output amplitude - line-level output (for compatibility with guitar amps) should be 1Vp-p. If you're controlling another synthesizer, adjust all the way up to
10Vp-p, or as needed.
R58 adjusts sine distortion of the LFO output. Adjust for a good sine curve.
R59 adjusts the DC offset of the LFO. Aim for zero offset.
R60 adjusts the amplitude of the LFO, from a slight flutter to drastic up-and down changes

Step 18: Video and Audio Samples!
Bear in mind that prior to building the Prism I'd never even touched an electric guitar, so I'm very much an amateur when it comes to playing it! Most of the people who
have tried out the guitar are also not guitar players and get similar results to me. However, I'm sure that in more capable hands this instrument will yield some impressive
noises!

Stay tuned as I add more multimedia!

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Step 19: Future Fixes and Revisions
There are a few little bugs to work out that still need to be fixed. The posted schematic and PCB will be kept up-to-date to reflect changes I make. The biggest problem is
a small amount of noise generated by the IR range finder. I've managed to get the noise level very low using a huge power supply filter capacitor and single pole lowpass filter at the input op amp, but I may upgrade to a double pole filter. I also want to add a very short "attack" delay to eliminate "switch bounce" when the laser is
"plucked."
Another big change that I am considering is to provide a separate oscillator for each "string." This would allow the Prism to be "open tuned", so that it can play chords. As
I wrap up this project I'm looking into ways of simplifying the design to fit such a change in the same space. Hopefully, I'll be able to yank out the old board and pop in the
new one...
I should also add that the Prism doesn't get along well with sunlight. Don't even bother playing it outside during the day, or in a brightly lit room. The ambient light will
cause the phototransistors to stay "on" all the time, preventing any tones from being generated. Perhaps when I get some time I'll figure out a solution, but in the
meantime stick to darkened dance clubs, bars, and basements...
If I get the time, I'd also like to add the following improvements to the Prism Laser Guitar:
1. Adjustable sustain and decay, so the last note played slowly fades rather than abruptly ends
2. Make the whole thing surface mount so that it fits in a smaller space
3. Add user-feedback LEDs (LFO frequency, selected waveform, etc)
4. Add harmonic or under/overtone generator?
5. Built-in delay effect? (similar to change #1 I suppose)
6. Possibly find an alternative to the IR Range Finder?

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Step 20: Special Thanks, and Resource Links
First off, a Big Huge thanks to my friend Dave, who gave me his old busted Gibson Explorer clone to hack up for this project. He also gave lots of advice on guitar playing
and how a guitar behaves, since I don't actually play guitar myself!
Thanks to my father-in-law, also a guitar player, who gave additional advice on how a guitar works and behaves.
A special thanks to Stephen Hobley, author of the Laser Harp article in Make 15. We chatted a bit and he was very helpful in helping me choose which direction to take
this project.
Thanks to Thomas Henry for his original VCO design based on the XR2206, and to Scott Stites for posting the design and how to use it on his site.
A shout out to all my pals at KWartzLab, our budding hackerspace in Kitchener, Ontario! If you're from the K-dub I encourage you to check it out!
Thanks to Instructables member gmoon for advice (and an excellent Instructable) on refinishing guitars.
And last (but definitely not least!) thanks to my wife for yet again letting me plunk down a chunk of change and a lot of time on another hare-brained project. Her hand is
also visible in the Refinishing step, gleefully chipping large sheets of paint off the guitar.
Important resources:
Thomas Henry's XR2206 VCO - upon which the Prism design is based
XR2206 datasheet - very useful to have, also contains a reference design used for the LFO
Sharp Rangefinder Datasheet
Google - to help me figure out what kind of guitar I was hacking up!
Mouser - for half the parts used on the Prism
Digikey - for the other half of the parts used
DealExtreme - a cheap source for lasers
Metal Supermarkets - a chain of stores in Ontario that sells metal to hobbyists
Sayal - a chain of electronics parts stores in Ontario

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

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Comments
50 comments Add Comment

theunexpector says:

view all 352 comments

Feb 28, 2011. 12:51 PM REPLY

Is it me or those schema and part list do not work, it ask me witch program I want to use to see it, have an idea guys?

jeff-o says:

Mar 1, 2011. 4:29 AM REPLY
To view the schematic you'll need Cadsoft Eagle, get it at www.Cadsoft.de. Or is your problem that they are downloading as .tmp files? In that case, try
renaming the file to what it was supposed to be.

Max "the bassist" Pratt says:

Feb 18, 2011. 7:34 AM REPLY

You would destroy such a beuty!!!!!
Just kidding nice project, might work on a variation as a side project =D

youngcustoms says:

Jan 22, 2011. 5:40 PM REPLY

I cant seem to open laserguitar.brd, laserguitar.sch, & prism parts list! Can U help me out?

jeff-o says:

Jan 22, 2011. 6:53 PM REPLY
.brd and .sch are Eagle CAD files; get a free copy of Eagle at www.cadsoft.de. The parts list is .txt, that shouldn't be a problem... Or are you getting .tmp
files? Try renaming them as appropriate. If that doesn't work, let me know and I'll email them to you.

youngcustoms says:

Jan 24, 2011. 2:21 PM REPLY

Sorry, I still having trouble with these!

jeff-o says:

Jan 25, 2011. 10:05 AM REPLY

Well, describe the trouble and I'll try to help...

ArtXander says:

Jan 2, 2011. 9:05 AM REPLY

Great man!!

Andreonh says:

Nov 9, 2010. 9:30 AM REPLY

How glossy would the paper need to be because im wondering if i am going to need to buy some very glossy paper online?

jeff-o says:

Nov 9, 2010. 10:17 AM REPLY
You shouldn't need to go online to find the paper. Glossy photo paper works well (I use paper marked "high gloss"), others have had success with glossy
magazine covers.

Andreonh says:
does it matter how long after i print it that i actually iron it onto our copper?

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Nov 16, 2010. 7:41 PM REPLY

jeff-o says:

Nov 16, 2010. 11:02 PM REPLY

I'm not sure. I always did the transfer within hours, to avoid the possibility of scratching the toner off the paper.

Andreonh says:

Dec 15, 2010. 10:13 AM REPLY
using these exact instructions i did this "laser printer and all" and i ended up with a barely transfered ink. this is very strange... are you sure it
doesnt need to be an inkjet printer

jeff-o says:

Dec 23, 2010. 8:12 AM REPLY

100% sure it must be a laser printer.
However, the toner transfer method can be a bit finicky. There are a number of factors that can affect the transfer - the type of toner the
laser printer uses, the "darkness" of the toner, the type of paper used, the cleanliness of the copper clad board, the temperature of the
iron, the pressure used on the iron, the amount of time the iron was pressed on the board...
So, I assume that the toner transferred in some places, but not others? Try cleaning the board really well with fine steel wool. That helps
the toner "stick" to the copper. Also try different types of paper. Some people have better luck with photo paper, others with glossy
magazine paper. Or, you could try the dedicated "blue" toner transfer paper.
Another thing to watch out for is air bubbles. I think, but have not confirmed, that air pockets can form between the paper and the copper,
preventing a good transfer.
Good luck!

Darwinfish says:

Dec 2, 2010. 1:22 AM REPLY
This is awesome. Makes me wonder what else this tech could power. Take a piano with a broken soundboard, some lasers... hmm... make that lots of
lasers...

jeff-o says:

Dec 2, 2010. 4:31 AM REPLY
A children's toy piano could be hacked into a laser harp. There's no point in using a full size piano, because the lasers can only convey on or off - not
velocity. It would be like playing a piano with a hammer.

Pie Ninja says:

Dec 1, 2010. 4:13 AM REPLY
I wonder if I can get the lasers mounted horizontally, rather than vertically. Also, you've probably been asked this multiple times before, but how much do all
the parts come to?

jeff-o says:

Dec 1, 2010. 5:58 AM REPLY

What do you mean, horizontally? Like, sticking out of the guitar? It's definitely possible, I'm not sure why you'd do it though.
The parts came to around $300 I guess, though some are now obsolete and hard to find.

Pie Ninja says:

Dec 1, 2010. 9:17 PM REPLY

Well, the spaces didn't work in the second bit of ASCII art, but you get the point.

Pie Ninja says:

Dec 1, 2010. 9:16 PM REPLY

Horizontally as in, instead of this:
|----- < laser
|----|----|----Like this:
_._._._._
||||
| | | | < laser

jeff-o says:

Dec 1, 2010. 9:31 PM REPLY

Yeah, that'll work as long as the sensors are lined up with the laser beams.

Pie Ninja says:

Dec 2, 2010. 11:00 PM REPLY
I understand if it would be too time consuming, but could you tell me what parts are outdated/discontinued? (And if possible, suitable
replacements)
I'd really appreciate it.

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

jeff-o says:

Dec 3, 2010. 4:26 AM REPLY
SSM2210 (IC10) and the XR2206 (IC1, IC6) will give you trouble. The rest of the parts are either available or have an easy-to-find
replacement.

Pie Ninja says:

Dec 5, 2010. 5:13 AM REPLY
Thankfully, there is one listing for the SSM2210 on ebay (which I am definitely buying tomorrow) and the XR2206 is, surprisingly, sold
at Jaycar (Australia's RadioShack, but with a crappier product range :P)
Thanks for the help, definitely going to post pics when this is finished.

Andreonh says:

Nov 29, 2010. 9:51 AM REPLY

another question... when printing from eagle do we need to make it mirrored or not?

jeff-o says:

Nov 29, 2010. 9:53 AM REPLY
The top side of the board should be mirrored, the bottom not. Try printing samples on thin paper or transparent acetate and line them up to be sure.

Visic says:

Nov 28, 2010. 5:02 AM REPLY

Just curious, but did you consider using a thermin type method to control pitch rather than the range finder?

jeff-o says:

Nov 29, 2010. 6:37 AM REPLY
Not really. Not only would it have been harder to implement, but you'd probably get interference from the player's body. The sensor really needs to be
uni-directional, and even the optical sensor wasn't directional enough for my tastes.

Andreonh says:

Nov 19, 2010. 10:33 AM REPLY

so my teacher wants me to ask if there is a difference between copper clad and copper foil... if you dont know its okay

jeff-o says:

Nov 19, 2010. 11:14 AM REPLY
Well, you can buy copper foil, with or without an adhesive on the back. But what you want for the PCB is copper-clad FR4, which has a layer of copper
permanently fused to a panel of fiberglass (on one or both sides).

Andreonh says:

Nov 16, 2010. 9:49 AM REPLY

okay im wondering how you solder such tiny spaces... are you using a smaller soldering iron/solder wire?

jeff-o says:

Nov 16, 2010. 10:22 AM REPLY
Yes, and no. I have a fine tip soldering iron, that tapers to about the same width as a component lead. The solder, also, is about that wide (but in the
world of electronics is a normal size).
There are a few other tricks that you can use, like applying flux to the connection, a tiny blob of solder on the iron, and touching the tip to the joint.
But in general, a quality fine tip soldering iron is the key. It doesn't have to be expensive, either. I used a $30 Weller iron for this project.

mrinc says:

Feb 1, 2010. 1:28 PM REPLY
How Much Would You Charge To Build The Circut With All The Components, With Everything else Except The Guitar And Ship To South Africa.
I Have An Unlucky Time With Circuts That Are Complicated.
Thanks

jeff-o says:

Feb 1, 2010. 2:15 PM REPLY

About $400.

Night910 says:

Oct 30, 2010. 4:50 PM REPLY

what about Louisiana?

jeff-o says:
Wait, I'm working on an update. Dunno how much it'll be, though.

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Oct 30, 2010. 6:25 PM REPLY

Andreonh says:

Oct 6, 2010. 10:37 AM REPLY

Hello! i am having trouble finding the ic10 on the parts list for sale please help me if you are willing =D

jeff-o says:

Oct 6, 2010. 11:13 AM REPLY
Wow, it seems to have become obsolete! I found some at www.utsource.net. Their buying process is more complex than is necessary, but they're
trustworthy and reliable. Let me know if you need help sourcing any other parts!

Andreonh says:

Oct 7, 2010. 9:41 AM REPLY
Also im wondering about item c22 because the 3u3 value is new to me or is it a typo... please clarify... and finally i am wondering about the quantities
of the parts in the parts list

jeff-o says:

Oct 7, 2010. 9:46 AM REPLY

Oh, that's a short form method of writing "3.3uF." So, 2n2 would be 2.2nF. 5k6 would be 5.6 kilohms.
What about the quantities? Whether they are correct?

Andreonh says:

Oct 7, 2010. 10:00 AM REPLY
IC1 XR2206 XR-2206 DIL16 exar 1
IC6 XR2206 XR-2206 DIL16 exar 2
im confused on if this means i need to get three of them or if i only need two? or what part of it means the quantity

jeff-o says:

Oct 7, 2010. 10:37 AM REPLY
Nope, you just need two XR2206 ICs. They are IC1 and IC6 on the schematics. I'm not sure what the "1" and "2" mean at the end of each
line, but it's not the quantity.

Andreonh says:

Oct 8, 2010. 9:46 AM REPLY
also i am having a LOT! of difficulty with the pinheads because my teacher is telling me that i need
"http://www.mouser.com/Search/ProductDetail.aspx?R=22-28-0042virtualkey53810000virtualkey538-22-28-0042" this im not sure
about... i am partially new to this so i will probably have a lot of questions

jeff-o says:

Oct 8, 2010. 9:51 AM REPLY
Well, the header connector in the link you posted has a built-in lock. That's a good idea, I suppose, because it will help keep the
cables plugged in. But, you'll also need the matching connector that has a little ridge to engage the lock.
I think this is the matching connector:
http://ca.mouser.com/Search/ProductDetail.aspx?qs=mrPiglD9aYKHkmsc%2fKlL3g%3d%3d

Andreonh says:

Oct 8, 2010. 10:00 AM REPLY
well im wondering is there another thing thats less complicated or more basic that would do the same job with a little less
complication?

jeff-o says:

Oct 8, 2010. 10:27 AM REPLY

Sure. you could use a terminal block like this one:
http://ca.mouser.com/ProductDetail/PhoenixContact/1725672/?qs=sGAEpiMZZMvZTcaMAxB2AF3qQv3QF5c1cqzdDV%2fmZgo%3d
Then you'd simply insert the wires and tighten the screw.
Or, you could go super-simple and just solder the wires directly to the board, but that could complicate troubleshooting and
final assembly.

Andreonh says:

Oct 8, 2010. 10:39 AM REPLY
the soldering directly sounds really easy too mess up... im moderately confused about this board but if it replaces jp 114 ill get it

jeff-o says:

Oct 8, 2010. 10:46 AM REPLY
Well, soldering directly won't be hard, it would just be a pain to desolder wires in case anything needs repairs.
Since I knew my board would be connected and disconnected multiple times until I got the bugs sorted out, I
decided to use connectors. If you want to avoid crimping all those wires, I think the screw terminals are your best
bet. They come in multiple sizes (two, three, four terminals...) and should fit in the same space as the headers.

Andreonh says:
okay =)... sorry i know im probably getting annoying but also
r33-r40, r58-r60

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/

Oct 11, 2010. 10:19 AM REPLY

jeff-o says:

Oct 11, 2010. 11:02 AM REPLY
Those are all the trim potentiometers. Are you asking if they're necessary, or are you having trouble finding
the right ones?

view all 352 comments

http://www.instructables.com/id/The-Prism-A-Laser-Synth-Guitar/