Step 2: The Circuit

Picture of 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.
Remove these adsRemove these ads by Signing Up
tejask2 years ago
can i gt the schmatic circuit diagram of the circuit above
jeff-o (author)  tejask2 years ago
It's right there under the text, called "laser guitar.sch." You will need Cadsoft Eagle to open the file.
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 (author)  theunexpector3 years ago
To view the schematic you'll need Cadsoft Eagle, get it at 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.
Andreonh4 years ago
Hello! i am having trouble finding the ic10 on the parts list for sale please help me if you are willing =D
jeff-o (author)  Andreonh4 years ago
Wow, it seems to have become obsolete! I found some at 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!
DrPizza7774 years ago
i have eagle, but the BRD and SCH downloads download as unusable temp files. what do i do?
jeff-o (author)  DrPizza7774 years ago
Have you tried renaming the temp files as .brd and .sch?
Broly2885 years ago
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 (author)  Broly2885 years ago
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.