Keyboard Build Log 2023

2024-04-24 – #Hardware #Desktop

Idea and Design
Build
Retrospective

Important

In less than two months (June 22nd 2024), the mechanicon in Frankfurt is taking place again for the second time after the pandemic.

Idea and Design

In late 2023 I wanted another keyboard. I like using split keyboards. But that’s not because they are split but because they normally come with a thumb cluster and ortholinear key arrangement. These features are also provided by most other ortholinear keyboards. So I decided to build something like a Planck keyboard but with a lower profile (choc switches) so I can also travel with it.

Build

PCB

For the PCU, I decided to do small changes to the MIT-licensed Horizon PCU instead of designing my own.

However, I wanted to have five columns per hand like the Planck instead of six like in this design. That way, the keyboard would be small enough to fit in the front pocket of my laptop bag. I also didn’t really want to change the electronics of the PCB because I don’t know about this magic. So instead I added holes that would allow to break off the last columns of the PCB.

Figure 1. Inspiration was the Corne PCB with the option to break off one column (source: Thomas Baart build log)

I know this technique from the Corne PCB as shown in Figure 1. It allows for more flexibility in using the same PCB. This is the only thing that I added to the PCB. And of course I also changed the image in the silk layer. At that moment, I thought the backside of the PCB will not be visible after the build anyway and so I didn’t put much thought into the image but I like how it is anyway.

Figure 2. Preview of the PCB in JLCPCB showcasing the break-off holes

The two major features changed in the inital gerber files (break off holes and silk layer) are display in Figure 2. That’s how I ordered it from JLCPCB. Five PCBs for under 20 Euros (because it was my first purchase).

Onto this PCB I soldered the MCU (Microcontroller Unit) which was some Pro Micro from berrybase. I also soldered the Choc switches onto this PCB.

Mid layer

Figure 3. "Postprocessing" after the 3D print didn’t fit the screws

In FreeCAD I constructed a mid layer that should act as a spacer between PCB and bottom layer. Figure 3 shows my first error: The holes I designed were too small and couldn’t fit a M2 screw. I decided to break away parts of the construction and hope that the middle layer will be kept in place anyway.

The screws that I needed were bought at "Modellbau Dersch". Construction shops don’t sell screws smaller than M3. I also didn’t want to order a big box of all sort of screws just because I needed a handful. For that the small shop in Wehrda was perfect: 10 screws for one Euro.

For the M2 standoffs, I removed them from an existing keyboard which had a lot of standoffs and where I don’t notice when four of them are missing.

Bottom layer

I also wanted to 3D-print the bottom layer. However, when I was at the makerspace in Gießen, I talked to people there before starting the hours long print and the guy I talked to used the laser cutter to create plates in his project. I thought lasers are inherently cooler than printers. So I took my FreeCAD project and exported the scratch as a DXF file which I then imported in inkscape just to export it again as a SVG file. I then took a leftover acrylic glass and cut my bottom plate within less than a minute with the laser cutter. As a nice side effect the acrylic bottom plate looks fancy and I can still look at the silk screen from Figure 2.

Figure 4. Combining the different keyboard layers

MCU box

Since this keyboard is meant as a travel keyboard, I can’t keep the MCU open because it could damage easily. That’s why I designed and 3D-printed a small box around the MCU.

One problem I encountered here is that the Horizon keyboard normally would have more keys at this place. This means that the box has to be slim enough to not interfere with the keycaps. However, I didn’t saw this problem until after the print. Luckily, the print fits just right.

Figure 5. Finishing the build

Retrospective

I think the final keyboard looks neat!

One thing I didn’t know beforehand: MBK keycaps sit VERY tight in these switches. If I were to do this again, I would go for hotswap sockets. Together with a switch plate, there should be nothing loose when thrown into the backpack. It surely would have made my case design way easier. It would have been better to solder cheap sockets instead of expensive switches which might not be reusable now.

Another thing I did was that I tried to solder one switch with very little solder and test its functionality through a voltage meter. That way I thought I could reverse a mistake early on. But this became somewhat of a mind virus: I put so little solder onto it and maybe also didn’t use the voltage meter properly and so the "functionality test" didn’t yield the right result. This left me in a troubling state. This is dumb, I should have just soldered the parts normally the first time. "Checking" the functionality and guessing in between if I already broke something wasn’t worth it. Of course saying that I should have just soldered it completely on the first try NOW is an easy call but I’m willing to make it anyway.

The last point I have is about choc switches. I’m not a fan anymore. If I were to do this again, I would have just hand-wired MX switches with a similar layout. I don’t think the extra millimeters in height are worth it to buy into more expensive switches and keycaps.

Despite all of this, I’m overall happy with the result. But now I need to get rid of four PCBs somehow.