Tri-Fold Writer

11/5/25

So a bit of major shift in the project scope...

After tinkering with the PG1316S switches, I had some major concerns about a few things

• Most importantly these switches are surface mounted, which inherently makes them far less easy to repair and replace. A genuine  concern given there are numerous reports that they have questionable reliability. The idea behind this project has always been that it would be as DiY friendly as possible and if its difficult for the average user to repair that defeats the purpose

• Also, these switches are quite pricey and quite difficult to source. This also applies to the key caps, which are even harder to find; this would require custom manufactured caps further driving up costs. 

Unfortunately the decision to not use these switches complicates things a bit. The smallest widely available MX style switch still adds about 30-40% thickness to the entire device. Making the device far less 'pocket-able' then I want. At that point, why not just make a thinner bi-fold device? 

We also came to the decision that the display we were thinking of using was just too low of a resolution. The display was small and ergo the text needs to be small and clear to maximize the usability. So back to square 1 on this too.

So with these revelations, I decided to take a short break from the project. Mainly to focus on some other projects around the house and to give some thought to the problem. To be honest, It was a bit frustrating. In the end I was really left with three choices:

1. I could just go with the scissor switches and hope that they prove reliable enough and the overall cost remains reasonable 

2. I could go with the standard low profile MX style switches and just deal with the thickness the best I could

3. Or, I could use the MX switches and rethink the design entirely to work around the additional thickness they add. 

I'm considering all these options. But during my testing of the gear hinge, I had an idea of another potential design. Instead of having display folding on top of the folded keyboard, having the screen sandwiched in-between the keyboard halves, integrated within the center hinge. There are numerous challenges with this, chief among them the fact that the width of the display directly correlates to the thickness of the device. And then there are challenges with ensuring we can fit the rest of the components within a smaller area. I've been sketching up some concept ideas, and on the surface, there seems to be a possibility that it could work if we can get the right display.  

Thankfully not all the work has gone to waste. The hinge design can still be used (with some modifications), and systems like the charging/power circuits can still be used even if the PCB design shifts.

So what next?

So all-in-all its been fairly discouraging to have such a major set back. But with any luck this new idea might pan out, and the device will be far better. So I'm returning to the drawing board, and will start designing around this new concept. There is a chance it won't pan out, but we won't know until I start plugging in real numbers and printing out a couple prototypes. 

For now, I'll leave you with a couple concept renders. Bare in mind these are in no way functional, purely made to illustrate the very broad design concept. 

10/28/25

Quick update:

• Upgraded printer to a smaller nozzle. Impressive results. Vastly improved the fine details of the smaller parts.

• Reverted some changes to the hinge, as they didn't play out like I thought. However the latest revision (2) is excellent. Very smooth and robust even using standard PLA. 

• Did some work with the keyboard PCB's, and getting closer to ordering prototype boards.

• Received PG1316S switches.Will be experimenting with them and printing caps 

• Testing of the power and charging circuit system is currently in process 

On Deck

• I will be working on printing a full mock keyboard enclosure as well as a mock PCB. Then temporary mount the switches/plugs to see how everything feels and fits. Hopefully a cheap and easy way to catch any simple issues before shelling out for real PCB prototypes 

• Need to finalize the routing of the main cable between keyboard and main board. And then work through finalizing PCB designs.

• Continuing to progress on 'bread boarding' power systems and display

10/24/25

So I ordered up a smaller (0.2mm) printer nozzle to replace my current 0.6mm one. My hope this will allow for much more fine detail in the hinge assembly, particularly the gearing. 

I made some more changes to the hinge design, mainly adding more support and locking both gear sets in rotation. Hopefully this will further eliminate any unwanted movement. I also redesigned the stops on the gears to hopefully be a bit more solid. The current case design also acts as a rotational stop. I also reduced the length of the gears by about 50%. This will hopefully reduce the slight levering effect that was causing some misalignment in my testing. Tolerances are tight between the rotating parts, so I suspect there will be further tweaking there.

After some playing around with a ribbon cable I came up with a possible solution to the slight tension that occurs when the keyboard is closed. The center hinge has been slightly hollowed out and the ribbon cable is double folded. This gives the ribbon a spring effect when either end is pulled and allows plenty of spare cable length to accommodate for the tension without having the cable 'bulges' at either end. I just need to make sure the ribbon cable bend radii in the middle aren't excessive; I may design in some guides to ensure no damage occurs during assembly.

Once I get the smaller nozzle, I'll be printing this revision, testing, and making any adjustments where needed. Once I am confident there aren't any further major revisions needed, I'll be shifting my focus to the keyboard PCB itself. I'd like to have a fairly complete keyboard PCB in my hands before I splurge and get MJF nylon prototypes made up of the hinge. 

10/23/25

After a few prints, I finally finished a proof-of-concept design of the hinge. As the name implies, this is primarily to test the concept and see if the hinge functions how I expect it to. And after a few tweaks I was very happy with the result. The folding action is very smooth and accurate. Despite this success, it is after-all, just a proof of concept; there is many tweaks and improvements needed. Especially to ensure proper alignment and reliability.

• After preliminary testing with FPC ribbon cable hot glued in place, there will be a bit more leg work to ensure that the cable folds neatly and the 'bulge' is properly hidden. There will also be some kind of protection of the exposed cable when the device is closed. There are no major pinch points or sharp angles which were the major concerns. Overall this portion went about as well as I thought it would, I knew there would be some additional designing regarding this. The good news is that this design seems like it will work given the correct design changes are implemented. I have a few changes in mind that can be integrated into the hinge assembly and/or the case assembly portion to solve these issues.

• The gear teeth are too small to be printed to the accuracy needed. So they end up kinda just being spikes than the proper profile. things still mesh surprisingly well, but I might tweak it more. I am going to try using a smaller print nozzle to see if I can get better accuracy. It's very likely I will get the hinge components made via MJF printed, so this may be a non-problem as that method is far more accurate than a standard 3d printer. However I'd still like to make the design accessible to the average DiY'er 

• Right now I threw in a rudimentary stop in the gear itself and it works, kinda... I need to design a much better and robust solution.

• The entire assembly and gearing can be downsized further by a few millimeters to decrease the overall folded thickness.

• There needs to be some refinements to ensure accurate printing (like the holes, edges, and etc). This is low priority at the moment and will be done at the very end.

All-in-all a successful PoC. Now we begin the process of refinement, and I'm sure this design will go through several more revisions

The next step will be finishing the design of the actual keyboard PCB and getting one of those made up. Once the main hinge set it finalized, I will likely get some prototypes manufactured from the aforementioned MJF printing process. In the end, hopefully we will be left with an actual working keyboard prototype. I may also make a second prototype utilizing the more widely available Kailh PG1232 (or similar) MX style switch. 

On another note, the screen test board has been soldered/wired up and we should hopefully getting that working and tested. The main goal here is mostly to confirm functionality of our circuit designs. Secondarily, we get to throw up a variety of text onscreen to see how things look and function. Will update with that once we get it running.

In addition we have received the charge/power evaluation board and are currently running tests; this should result in a completed circuit for the charging and power related systems. After we hammer that out, the rest of the circuit design should progress fairly quickly. Fingers crossed we get a working V1 prototype board in hand in the near future.

10/21/25

We ordered up some components and developed/ordered a PCB test board for our screen. This is basically to test the functionality of our system and play around with the display/ESP32 combo before spending the time and money on the full 'motherboard'. More or less a fancy bread board to allow us to test  part of our circuit design. We should get those PCBs in a week or so. Should give us a good indication if our choice in screen type/size was correct, and let us change it out before we get too far. 

In addition we also purchased a battery/charger evaluation board. Seeing that the battery and power circuit is arguably the most critical we are ensuring that our design is safe and efficient. This is more of a tool than a component, allows us to gather data on our designs and also give us an easy way to experiment with different parameters of the charging system.

I've also purchased a handful of the Kailh PG1316S/M to do some initial tests on. I still have my doubts on these switches, but given they are the only real available option on the market for it's size profile, I'll give them a go. 

I'm finishing up the initial design for the newest hinge design, which has changed a lot from the early concepts. I just need to buy some hardware and start printing for the first test run. There are a lot of tweaks needed now and I'm sure more stuff will come up, but the first prototype is to test the general design concept and confirm whether it works in practice as well as it does in my head.

This concept barrows a lot of concepts from the DM30 and some other folding keyboards from the community. I really wanted to work in the gear design idea from the DM30, it really helps with axis stability and cleans up a lot of erroneous movement slop when opening/closing. I anticipate some tweaking on the gear design itself, given the small tooth size, I'm guessing there will be some challenges printing accurately. My back up plan is to buy some commercially available gears and integrate them into the housing rather than printing them as part of it.

I'm considering the possibility of getting the final design manufactured via Multi Jet Fusion (MJF) out of nylon. The cost may be relatively low, and this method would provide a extremely robust and accurate part, which may be critical especially for that gear portion. I've had great luck with this printing method in the past.  In a perfect world, I'd love to manufacture the entire outer shell parts from nylon and MJF, but I suspect this will end up being cost prohibitive.

I'm also work on the 'stop' mechanism; basically ensuring it opens and stays flat.  The way it's currently designed requires it to be on a flat and hard surface to remain open. This kind defeats the point of a ultra portable device where the use-case is likely to require the use of uneven surface ( ie your lap). This was a challenge with the DM5 and DM30 writers, and will present a interesting problem with this as well. I'm working through some ideas for latching systems and see what I can come up with.
 

The outer case and keyboard cover are still a W.I.P. But this gives an idea of the general concept. These components can be easily 3d printed and swapped for some customizability. Also allows for the keyboard to be easily adapted to a wide variety of projects by simply modifying the case; allowing the hinge to remain consistent.

Now this design is notably missing a MCU unit, as the idea is to have that externally. I'm working through various options for output headers. There may be various versions of the PCB to allow some flexibility (IE FPC ribbon, USB, pico-blade, and etc). Depending on the progress of this hinge mechanism, I may branch on later to design a more complete keyboard with a MCU, but we'll see. 

Obliviously there will need to be multiple rounds of the prototyping, but the concept is solidifying a bit!

10/16/25

So its been a couple weeks, and I thought I'd throw up a small update. Although fair warning, there isn't much in the way of progress. 

Admittedly, there has been little movement on the project overall. Primarily because the team has been has been pretty busy with personal things and work, we haven't been blessed with a whole lot of free time to work hobby projects. Hopefully things will settle out a bit, and we'll make some actual progress soon.

Again, the main hurdle is the electronics, specifically the control board/screen. While I could maybe design a workable product, to achieve the quality we want I'm leaving that portion to the more qualified individual. So instead of tiddling my thumbs while that gets worked on, I've shifted my focus to the other challenging bit of the mechanical design. The keyboard and the hinge mechanism.

Folding Dev Keyboard
Recently I thought maybe I'd make a 'quick and dirty' concept utilizing an off-the-shelf folding keyboard and a raspberry pi. To help figure out ergonomics and such. But after some digging I was surprised to find that there wasn't really any folding keyboards of that type which were entirely wired and didn't have BT and batteries. Which gave me an idea. Instead of designing this keyboard as a fully integrated part of our device why not design a sort of 'dev' fold keyboard. Basically a barebones folding keyboard PCB that can be integrated into many projects easily. The focus being something geared towards the maker community.

I have several sketch concepts I'm working through of what that might look like. The greatest challenge being the development of a reliable and easily manufactured hinge mechanism. 

9/21/25

Just a small update. Most of the last few days has been spent researching and discussing components and circuitry. The primary focus has been on the main control board. We are also in contact with a PCB manufacturer to get the final design shipped fully assembled and soldered. The 'main board' is the main focus right now, and it's a big hill to climb.

In theory, the main control unit is basically a self contained unit. So hook up a power source and an input device and it can function as a writing device. This means that its possible to utilize that base control board in any number of form factors. 

Charging Circuit

This is what we are considering as one of the most critical aspects of this and thus, most of the work has been on finalizing this. Essentially selecting battery type and designing the charging and power circuits within the board. Making sure everything is safe and will be powered sufficiently. A lot of technical details here, but I'll write up a more significant run down once we hammer out a more finalized design.

ESP32/MCU

The original plan was to use a ESP32 dev board, but now that the 'team' has a much more knowledgeable EE, we are likely are going to skip right to integrating the ESP chip directly onto the PCB. This a couple advantages, but chief among them is this will allow us to cut the size of the board by 30-40%. 

Keyboard
I'm designed preliminary boards based on the PG1326S switch. The preliminary PCB design is complete and is super simple, considering there isn't going to be an onboard MCU. However I want to do more research on the switches themselves. I've read that they may not be overly reliable long term. The alternative is one of the many super low profile MX style switches, but even those will add a noticeable thickness to the overall design. The PG1316S are not cheap (0.75$ / switch), but I might see if I can grab a couple to play around with and test.

Here is a glimpse at the first concept design for the housing. Obviously there is still some prototyping to do to hammer out the hinging mechanism, and it doesn't have IO, but the concept is there. We are sitting at about 8.5mm thick for the keyboard assembly and about 30mm for the entire unit (closed). This will likely fluctuate as we move forward though. 

Also should note that the current keyboard layout is for demonstration purposes only. Given the size, we will have to tinker with layouts to find which setup is the most comfortable to use.

9/17/25

Made some changes to PCB to reduce the footprint and the thickness.

Rang up an old co-worker who has far more experience with electrical  engineering and PCB design and they are lending some assistance get this to a working reality. Hopefully a little collaboration will make things easier/faster. The keyboard is definitely in flux, as I would like to use the scissor switches, but I'm not entirely convinced of their reliability and availability.

I know I promised no 'vapor-ware' renders. But I drew a beginning concept of the folding keyboard case. Obviously it's missing some major parts, but gives a good idea of the form factor I'm shooting for. Right now we are sitting about 35mm thick, but I want to continue to shave off thickness where I can. However if I abandon scissor hinges in favor of a standard low profile MX switch, things will end up thicker than expected.

 I'm also currently experimenting with micro detent hinges, as they offer a simpler solution and eliminate the need for lid closure latches/magnets. The downside being, of course, limited opening angles.

The priority right now however is the main board and the case/hinging components.

9/16/25

I had to step away from the project for a few days, I was getting a little overwhelmed. I was having a hard time deciding where to start and where I wanted to see the project go. Particularly, the form factor and the keyboard. How things fold and move, and how I can make it as portable as possible with the tools I have. I still don't a have a concrete idea yet, but I figured regardless of the direction I take one thing will probably remain the same: the 'motherboard'.

I've managed to design a preliminary PCB board based around the ESP32 and NewHaven display. I'm having a second more practiced set of eyes look it over, refine, and possibly bread board out a concept. I'm positive things will change and move around (ie the battery plug)....But its a start, and at the very least it gives me an idea of the foot print needed for an enclosure. 

9/9/25

A continual challenge I have with design work is my tendency to 'start over' with designs and concepts. These 'writer' decks are a great example, my workspace is littered with prototypes and designs in varying degrees of completion. 

After tinkering more with the MicroPad design/PCB, I've been forced to admit that I'm not a huge fan of the overall design. The one handed concept definitely has a niche use case. I can definitely see it being useful in many scenarios, but I'm just not super satisfied with it as my own personal device.

I find myself a bit discouraged abandoning/pausing yet another concept. I'd like to get one of these across the finish line AND be personally satisfied with using and making it. Although to be fair to myself, each failed attempt I come away with greater confidence, more refined ideas, and greater knowledge of how to better design the systems involved. Still, its difficult to regain the momentum and motivation to go back to the drawing board. Thus, is the unfortunate plight of tinkerer with ADHD.

Pity party aside, the last several days have been spent re-evaluating the project to better understand what I actually want to pursue. I found my sights firmly fixated on the enigma that is the 'trifold'. A form factor I love and have attempted in the past, but quickly pivoted away from because, admittedly, it was a bit overwhelming. But I feel more equipped to try to tackle it again.

So I've been concept sketching and figuring out the game plan.

Keyboard

One of the biggest challenges of a device like this is the keyboard. Traditional mechanical switches, even 'low profile' ones, result in a device that is just too thick to really be considered 'pocketable'. Alternatives like custom laptop scissor and membrane keyboards are far too complicated and expensive to be practical for a DiY/niche device.

Very few options exist when it comes to user buildable ultra low profile switches. And those that do, have availability issues. The best option currently is likely the Kailh PG1316s. They aren't perfect, Kailh still seems to ironing out issues. They aren't particularly cheap and they are a PITA to solder, but they allow me to achieve a keyboard of the ideal dimension.

Oddly enough, the keyboard is actually one the more simpler parts of this project when it comes to PCB design. And things can be tweaked to work around any changes. So while I have general direction, there will be a lot more research to solidifying the design and parts selection.

Screen/Electrical Comps

In the past I've been relying heavily on the Inkplate hardware and the work of the team at Zerowriter. However because of the overall size constraints I'm diverging on this device. I plan on building the system from 'scratch'. This is the first step I'm working on now: bread boarding and testing functionality. This will allow me to test things like ideal screen size/type, memory utilization, I/O and etc before spending money on an actual PCB.

The end goal is to have a complete PCB 'motherboard' that contains everything including the screen. Once I confirm everything will work how I want it to, I will start the process of PCB development and final parts selection. I've skipped this step in the past, so it'll add a significant amount of development time. The focus right now is primarily rudimentary hardware application.  I plan to try to integrate some of the many open source writer firmware GUI, but we'll cross that bridge when I get there.

Current hardware design specs:

• ESP32 Based

• SD internal / External USB C storage

• FSTN (Reflective) display 

• 1000mAH  + internal lipo battery

I'm experimenting with a rather small FSTN (New Haven NHD-C12864WO-B1TFH#-M) screen right now. These are great because they offer great visibility in bright light environments, have low power draw, and optional backlighting. I'm certain there will be changes will this, especially after testing. I have doubts regarding resolution and refresh rate, but this is just a starting point; and I happen to have one of these from another project.\

Enclosure

The enclosure here offers one of the more unique challenges, especially considering it with the restrictions of easily accessible manufacturing techniques (aka 3d Printing). It's early stages, but its looking like the design will more closely resemble the Pomera DM5 rather the DM30. The DM30 (and many of the trifold keyboards you can buy online) use a staggered keys to 'interlace' three parts to form a seemingly one piece keyboard. While this is doable, I'm opting to forgo this to simplify the design. Instead my thought is to design the folding halves to feel more a long the lines of a split keyboard. 

The hinges also present an interesting challenge. I think I might make post specifically talking about the fundamental challenges these types of devices face when it comes to hinge design and how devices like the DM30 ingeniously solve them.  For now I'll just say, eliminating the requirement that the keyboard halves 'slot' together into a single keyboard without a gap greatly reduces the complexity of the hinge design. 

Overall, the current goal is a sub 24mm thick device (when folded up). I'll probably never be able to match a true injection device when it comes to slim design, but want it as small as possible while remaining reliable and easy to repair. I have several ideas of how to implement several aspects of the design, but we'll see how this start to come together

Conclusion

It feels good to be working on this concept again, it has always been my unicorn when it came to writer decks. And who knows, maybe this time I will actually get this one over the finish line! I'm gonna try to limit any updates to when I have some actual physical progress and try to avoid things that feel like vaporware hype (concept renders and etc).