Board games

As for my damp project, I use KiCAD for schematic entry, board layout and gerber creation. I've tried a few different packages and this one is free and unlimited. Like all CAD software it has a few quirks, but once overcome it allows the design of a PCBs beyond the usual rectangular two layer 100 component designs that some of its peers are limited to.

At the headstock end, the board is going to have 20 LEDs across by 5 LEDs high. The board needs to be slightly trapezoidal to allow for the increase in width as the neck continues to the body. At this point I can either design another 3 trapezoidal boards, or I can make thin 20 by 1 LED boards and then just space them further apart as they reach the body. I'm opting for the strip boards as this will keep the costs down.

Either way, the connections between boards needs to consist of five data lines and at least one power and one ground. With several amps being consumed by these LEDs, I am going to keep to five power and five ground so that each row has its own power lines. This should keep the incremental resistance down without having to resort to server blade power connectors.

After spending time trying to find 15 way connectors that are humanly solderable and less than 2.5mm or so high, I eventually decide that the only way to join these boards up is by individual wires. I don't like it, but on the other hand, I don't want to fork out for a 600mm long board either.
The final head-end board schematic looks a bit like this:

The board design looks like this:

The pads for connecting to the previous set of boards can be seen at the left hand end amongst the first 3 or 4 LED columns. The thin end will be approx 5mm from the nut when installed. LEDs are on the top side, and the decoupling capacitors are on the other side.

The individual strip board schematics are surprisingly similar, but with only one row of LEDs! Here is the single row board design, the data interconnects are at the far ends (to keep the data wire length to a minimum) and capacitors again are on the other side:

Finding space for the interconnect wires was a little more tricky on the single row board as although there will be space between them, both the top and bottom rows will be at the edge of the neck. This means the bottom row will have to have the boards fitted back to front so that the interconnect 'tabs' will stick up and will mesh together with the fourth row

Here are two boards laid top to tail to demonstrate how the interconnect pads are interleaved in order that it can all fit in the space provided.

It will be a tight fit where it joins to the end board, but will get easier as the spacing relaxes.

Using KiCAD, the board layout files are converted into gerbers (and drill files) for the PCB manufacturers. A really handy feature in KiCAD is that it comes with a separate gerber viewer application. This can be used to double check that all the layers required are present, sizes, scaling and thickness correct and no unsightly overlaps between layers. It's like printing a word document on paper - your eye is always drawn to the typo.

The boards are going to be made by PCBWay. They do a good job at a good price. Amongst the options they offer, different solder resist colours are available. For good contrast I am going for black solder resist.

When they arrive, I need to solder 400 LEDs and 400 capacitors on :-(