The Prism: A Laser Synth-Guitar

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.

Comments

[tejask]

can i gt the schmatic circuit diagram of the circuit above

[jeff-o]

It's right there under the text, called "laser guitar.sch." You will need Cadsoft Eagle to open the file.

[theunexpector]

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]

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.

[Andreonh]

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

[jeff-o]

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]

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]

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]

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]

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]

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]

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]

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]

Sure. you could use a terminal block like this one:

http://ca.mouser.com/ProductDetail/Phoenix-Contact/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]

the soldering directly sounds really easy too mess up... im moderately confused about this board but if it replaces jp 1-14 ill get it

[jeff-o]

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]

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

[jeff-o]

Those are all the trim potentiometers. Are you asking if they're necessary, or are you having trouble finding the right ones?

[Andreonh]

im having trouble finding the right ones

[jeff-o]

OK, I'll see if I can dig up some part numbers...

[Andreonh]

okay nevermind... i got it handled... but i need to know where you found you short lasers because the only ones ican find online are way too long

[jeff-o]

Sure! Any one of these should work:

http://www.dealextreme.com/details.dx/sku.13378

http://www.dealextreme.com/details.dx/sku.46391

http://www.dealextreme.com/details.dx/sku.5900

And actually, they may work better. If you use IR phototransistors instead of visible light (like I used), then your guitar should be much more resistant to interference from ambient light than mine was. Since I chose to use green lasers I needed to use visible light phototransistors or they'd be "blind" to the green wavelength. What I didn't realize is that in bright light my sensors basically could not turn "off."

But, IR phototransistors and red lasers should play together nicely.

[Andreonh]

thank you sir for all of you help =) i finally have the partlist and board ordered... but i will say that figuring out how to turn the brd file into gerber files was quite ridiculous! haha

[jeff-o]

Wow, it's great to hear that you've made so much progress! I think you might be the first to follow these instructions.

And yeah, converting to gerber files can be tricky! So many things to check...

[DrPizza777]

i have eagle, but the BRD and SCH downloads download as unusable temp files. what do i do?

[jeff-o]

Have you tried renaming the temp files as .brd and .sch?

[Broly288]

Do I have to make thes images black and white to transfer them seems like a stupid question but i need to know

[jeff-o]

It's best to print directly from Eagle. When printing the top layer, make sure that only the top traces (in red), the pads and vias (green) and board outline (white) are visible. You can select which layers are visible by clicking the Layers icon in the top-left of the toolbar. When you hit Print, a dialog box will appear with a few options. Make sure you select "Black" and "Solid." For the top layer only, also select "Mirror." To print the bottom layer, make sure that the bottom traces (blue) are visible along with the pads and board outline. In the Print dialog box, just "Black" and "Solid" should be selected.