The most challenging part of all this wasn't creating the schematic and deciding what parts to us. The challenge was in laying everything out on a PCB. This was further complicated by the need to create a single sided PCB layout so anyone could build this on a perforated board/ peg board/ breadboard (for the sake of this istructable we'll call it a breadboard). If i had done a two sided PCB then routing the traces wouldn't be an issue on such a basic circuit like this. In the end i played around with a couple of revisions to the layouts of the components before settling on Rev 2. Rev 1 was laid out in, what seemed to be, the easiest way i could lay it out and run the traces. With little consideration on how the user will interact with the board. On Rev 2 i decided i needed to focus more on how the user will handle it so i focused the part arrangement on placing key items like the terminal block, USB connector and power switch. I also thought it would be nicer to have the LED indicator in the middle of the board.
With a breadboard layout in mind i have included a PDF file of Rev 2's PCB layout without the copper fill. I picked up a Dual Mini Board Breadboard
from Radio Shack for about $2.19. This Breadboard is just slightly bigger then my PCB layout. Best of all the PCB layout lines up to the grid of the Breadboard. So you'll be able to print off the PDF of the PCB layout below and overlay it onto the Breadboard.
Now to get things pieced together.
Once you print the layout cut it down to size and tape it to the side of the board without copper pads. Line up the bottom right corner of the layout with the bottom right corner of the board. Hold the board and layout up to the light so you can see through the paper where the holes are and get everything lined up. To help ensure the holes all line up take one of the components and use it to punch all the component holes out. If things are not quite matching up then make adjustments as needed.
For the most part you will be able to solder the components together similar to the PCB layout but there will be some sections where you may have to make adjustments. We'll get to that in the next steps. I'll break the assembly down into several steps to help insure you get everything plugged into the right places and soldered together.
I've included the PCB files for Rev 2 below in extended Gerber, PDF , and Eagle CAD files if you want to try etching your own board. I've also included a Fritzing
file of the REV 1 Board which has a simple prototyping breadboard layout if you want to prototype it before putting everything onto a PCB or peg board. The finished board is only 40mm x 40mm. As you can see there is still a good bit of open space on the board. It can be made much smaller for final PCB production. I did consider having the resisters mounted on end to help shrink things down a little more. But we don't want to make things too small otherwise it becomes difficult for the hobbyist to assemble. I hope to get money together and have a small production run of boards made in the near future. I may get through a couple more of revisions before that happens.