laser-synthitar from a guitar-hero-like toy guitar

I was very inspired by all the youtube videos of laser harps but i found them all too big to bring along for a jam session or they needed a complicated setup and a pc etc. I thought of a guitar with lasers instead of strings.
Then I found a broken toy guitar similar to a guitar hero controller at a flea market. I'm already gathering too much electro-junk but i had to make something out of this. With some cheap laserpointers I was ready to make a

Laserguitar Synth
or a laser-triggered analog synthitar

No computer interfacing, no microcontroller, just 3 oscillators (its a first prototype, I wanted to keep it simple and started with 3) that are triggered by 3 photodiodes and 3 lasers. The buttons on the neck are used to change the pitch.
I'm a beginner in electronics but i had made some 555-Circuits so far, so i used 555s as the oscillators, the square waves sound similar to e-guitars. To mix the 3 oscillators i used an opamp as an audio mixer.

It looks messy, with exposed electronics and duct tape and hot glue and it sounds as ugly as expected but im glad that it actually works. Its a first prototype and proof of concept. Now that I know it works, I will probably make a next version.

This is my first instructable and english is not my native language, so plz be nice :)

Video below: too bad that i suck at playing it, but you can see it works.

Please vote for this instructable at the art of sound contest...

Step 1 Materials you need

- a toy guitar or some other guitar-shaped casing
- ne555 ICs - as many as you want "strings" on your instrument
- an opamp
- an inverter chip for between the photodiodes and the 555s, i used a 74ac14, with that 6 "strings" would be possible
- 100K pots for tuning of the fret buttons, this guitar has 5 of them
- 3 x 10K pots
- 0.1 uF capacitor
- audio jack
- perfboard

for each oscillator or "string" you need
- cheap laserpointer
- IR photodiode
- 100K pot
- 500K pot
- 4,7K resistor
- 1M resistor
- 2 x 10K resistor
- 0.1uF capacitor
- 0.2 uF capacitor

- solder
- hot glue

Comments

[Chrishugh]

This is awesome, you even played a little smoke on the water. I'm inspired.

Ausgezeichnet, und auch mit eine classiche Lied. Nun will ich ein machen.

[datenkrieger]

It's been a while since I updated this, my laser synthar stopped working some time ago and i haven't fixed it yet. The part with the photodiodes and the inverter ic seems to be the problem. Just as a warning, you will have to experiment to make it work.
Maybe the solution is to use the remaining unused opamps of the quad opamp for amplifying the output of the photodiodes. Maybe I give this another try one day but i have no time for that atm. But wish you Good Luck.

[timnolan]

This is unrelated but until I read it I had no idea you weren't a native english speaker.

[macattackct]

Does anyone know where I can find instructions for a laser harp?  Detailed instructions.  I want to modify this synth with the harp so it has no need for buttons.  I also want to use and arduino.

[king7pin7]

Hello, just wondering what type of photodiode you used/recommend for this project?

[lukaj2003]

Great Instructable! I was thinking of taking a look at the local flea market in a few days time to build this and was wondering if you could upload the eagle file or make a more simplified circuit? I have some electronics experience, but I can't make heads or tails of it. Keep up the good work!

[Virtual Adept]

Do you have larger images of the schematics? I've been trying to get a better view of the oscillators, in particular how they're hooked into the laser triggers, but the image is blurry enough that I can't make out how they're patched together. I've been trying to figure it out for a week but haven't had any success yet.

[datenkrieger]

sorry for that but if you click on the "i" on the top left of the image and then "original file: (809x445) 12 KB" you get the original GIF file in full size. It gets blurry when it's resized automatically, but the original file has all the details. Basically the trigger is connected to the reset pin of the 555. I found that the laser trigger circuit is not working reliably when the 9V battery is not brand new. I recommend to swap the 10K resistor and the 500K pot so it can be adjusted better (pot can be another value) but i have to test it yet. I will post the changed schematics soon.

[Virtual Adept]

Hey - thank you, I missed that. Much better! That makes sense. I'll give it a shot in the lab this week. I'll hunt through the parts bin at the lab and see what pots I can dig out. Maybe there are some hidden in there that'll work better. I'll let you know what I come up with.

[jeff-o]

So what are your plans for the next version? I'm impressed with what you accomplished here as a beginner in electronics!