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The purpose of this document is to describe my experiences developing the Ergo S-1 wireless keyboard that lead to it’s release as an open source project.

Preface

I, like many others, found myself unemployed October 2020. The engineering job market in Houston was a little thin at the time, so I decided to take the opportunity to tackle one of my more aspirational bucket list projects. I had been a keyboard enthusiast for years at this point and saw an opportunity in the existing products on the market (both commercial and hobbyist) to make worthwhile improvements on what was available. I roughed out a schedule to have the project finished in six months.

Brainstorming

My first step was to decide what price point I needed to hit to be competitive with other offerings on the market. This is an important first step because it will influence every single decision you make on the entire project from materials to design complexity.

I then spent a week roughing out conceptual models, similar to how clay models are made for new car designs. I’d start with a concept in my head, whip up a rough model on the computer, then imagine it in meat space and usually say ‘this looks like crap’ and iterate. This was the first time I really gave any focus to the aesthetics of a project and was likely more challenging for me than it would be for somebody more artistic. My projects had always started and ended at the simplest, most practical shape possible. I ended up taking a lot of inspiration from multiple open source projects like the Ergodox and the Dactyl as well as commercial products like the Advantage and the L89.

I also put some thought into the manufacturing processes I was going to use. I spent a lot of time researching thermoforming at first, but ultimately my focus became MJF for the keywell (switch retention is the most critical dimension in the design) and FDM for the case. FDM was chosen mostly due to the small production scale I was planning on. In general, manufacturing processes go from 3d printing –> thermoforming –> injection molding as you move up in production quantity.

I investigated designing for a thermoformed ‘skin’ over the printed case, but that idea was ultimately scrapped due to material availability of the sheet goods. The temperature requirements of thermoforming would have caused me to abandon PLA for the FDM process, which was otherwise a suitable material choice.

Keywell

This is where I initially expected to spend the most time. I started the keywell model first but most of the iteration happened in parallel with the case design.

During the process of iterating on key angles and positions I quickly realized that I wouldn’t be able to deliver the same typing experience across all of the different keycap profiles that are available. Initially I wanted to keep the design compatible with all the keycap profiles on the market, but eventually decided to narrow that compatibility to the most available profiles so my customers would have the easiest (and, importantly, cheapest) options open to them if they wanted to customize their board. Not doing this would have compromised the out-of-the-box ergonomics of the product.

This is also when I was experimenting with different switch retention mechanisms. The difference between a good fit that can hold onto the switch when a keycap is being removed, an overly tight fit that is prohibitively difficult to insert a switch into, and a loose fit that pulls out was a matter of a few thousandths of an inch. That is why products with injection molded keywells, like in the Advantage or L89, hot glue the switches into place. These kind of tolerances are difficult to hit with 30+ switches in any process.

Case – Basic Shape

Once the keywell models were far enough along, I started focusing on nailing down the shape of the case. Once again, this was a heavily iterative process. The first dozen iterations all included the necessary draft angles and geometry constraints of thermoforming, but that was eventually dropped in favor of FDM. At this point I went out and bought an ender 3 from microcenter. I had never used a 3d printer before, but my intention was to test multiple units later on for actual production.

I was regularly getting budgetary quotes for the different components of the design to make sure I was in the ballpark of the price point I wanted to hit. This is when I realized that MJF was not going to be the right process for parts of this size. For some reason I remembered MJF being priced similarly to FDM, but I had only used the process once before and I must have just been lucky.

Once I limited my manufacturing process to FDM, the keywell and case became one integral part to save on cost.

EMC Design Research

My two choices for PCB design software were KiCad and Eagle. I had used KiCad for some earlier projects, so I had some familiarity with the software and with circuit design in general. I ultimately chose Eagle for this project, as it has some specific routing features that I needed for the flex PCB that, at the time, were absent in KiCad.

I was also planning on obtaining FCC certification for this project, and had some idea that this is difficult to do.

I spent 3-4 weeks going through the modules on https://learnemc.com/. I felt like I was in college again with a lot of the theory but, overall, this was a positive experience. I used a handful of other references but this was my primary source of EMC information.

Split Case for Printing

Up to this point the models I had been printing were solid to make printing easier. Now I began breaking the case up into multiple parts that could be printed separately and assembled. I spent a good two weeks experimenting with different places to break the model up into two or three pieces. I put some effort into minimizing  supports to make cleanup easier but largely planned to address that after I finished the first prototype.

Design Mainboard & Keywell PCBs

One of the big features I was excited to work on was designing a polyimide PCB for the keywell. My design process eventually lead me down the path of mesh flattening. Turns out the software that does this is a huge, and almost completely proprietary, market in industries like clothing and boat sails. The pricing for the commercial software that does this was INSANE (i.e. normal industrial software prices). Luckily, mesh mixer can be made to do a good enough job with the right input.

I identified several key features early on that I knew I needed to incorporate into the design, which I plan on writing a separate article about later.