PF68 68 key keyboard with LCD, RGB, captured hot swap sockets by GH_Leslie

Last crawled date: 3 years ago

This came about after seeing various hot swap boards that didn;t work how I wanted.
After a lot of false starts using other designs I started from scratch and came up with this. The Hot swaps are held captive between the "pcb" and base plate so they can actually function as hot swaps, holding themselves in place. Best of all, no pcb to be damaged during swaps either.
Geekhack page with a bit more documentation about this project:https://geekhack.org/index.php?topic=109345.0
Printing test and template for the socket system is here:https://www.thingiverse.com/thing:4791698
Warning!!!!!This is as done as this project will get. If you want help it's better to catch me on GH however don't expect much help as I don't recommend actually building this as it is, remix it, use someone else's remix. The difficult part of the design is done but I'm burnt out on this project.
Warning #2
There's a lot of info here and it's necessary if you plan on building this.
Take note, there is NO FIRMWARE included, there is a keymap but nothing more, this is because how you wire from the PCB to the Teensy changes the firmware and it's honestly better to remap the firmware than try to redo the wiring. It will take a while but worth it, especially since once you do it you can do any board you want. This is why no one includes firmware, you would have to micro manage every last wire.
Notes: (Important stuff!)
While mine is done, this is a horrible project if I'm honest. I'm posting this so others can use the hot swap system and steal ideas but it's not an easy build, the wiring channels are really, really tight. Also note that unless you duplicate my exact pinout your firmware will not work, so it's a lot of tedious bits that if done wrong will need reworking. Also unless you have a large printer you will need to cut up the body. For RGB I simply drilled a hole through the base and foot and routed power, ground and signal, to get RGB underglow, it's not built in, just attached to the bottom (sorry no glamour shots, this was mostly to see if it worked). The mini B cable into the Tensy was expected to be used, I ran out of room and patience and just soldered direct to the board, a bit more hacking with a hot knife or minor changes and it could work but after doing it, I'd probably just solder it direct again.
Bottom line, remix it, don't use it as is.
It was a nice idea and it works, it's just not easily reproduced.
Features:
Very low profile, the body flat and extremely thin (11mm to top of plate, less than 1/2in).
Easy to print, (near) vertical walls means no stairstepping
Kailh hot swap sockets are locked in place yet easily replaced if they go bad.
PCB and plate mount switch compatible (no more trimmed legs!)
LCD to display layer and hotkeys
Teensy 2.0 with QMK so it's programmable.
RGB (sort of)
Port is a Mini B, Micro B or Type C depending on choice of breakout board (Adafruit).
Trim is replaceable for easy color swaps, I have two types, flat/flush and pencil grooved and is replaceable without no disassembly of the keyboard.
Status:
Everything printed, tested and working.
Parts needed:
About 1.1kg of plastic (see below for recommendations)
Teensy 2.0
0.91 Inch I2C SSD1306 OLED Display (Amazon)
Kailh Hot Swap sockets
Adafruit USB breakout board (see below)
rubber feet (10x10x2.5mm Kitchen Cabinet Door Pad silicone squares, amazon)
wire (I used solid core cat5 for the pcb and an old usb cable for the breakout)
solder
Switches and keycaps
3x M5x15mm bolts (or similar, just put them in hot to create new threads)
15x #2 screws (or similar, just put them in hot to create new threads)
Flux, you need flux to tin the hot swaps, it's MUCH easier. Rosin core will clog them if you rely on that one to tin them.
Breakout board links (available from other places)
Mini B - https://www.adafruit.com/product/1764
Micro B - https://www.adafruit.com/product/1833
Type C - https://www.adafruit.com/product/4090
:::::Tips:::::
Printing
Petg works, but at this scale it can be a bit of a challenge. Forget ABS, too large and too much shrinkage. If you plan to chop it into parts ABS and PLA are fine, but nothing really likes sticking to PETG.
Beware stuck support under the LCD, the top has a habit of ripping off the overhang, be gentle here. It shouldn't be a huge problem on PLA but it can be on PETG.
PETG will give you a more satisfying thunk, more like a plastic board with an aluminum plate, almost as stiff as one as well with 30% infill. PLA will give you a higher pitch sound but will also be stiffer and easier to print. It's also more likely to deform over time, hence my use of PETG. If you can do it as a single part, I would use PETG again, it just sounds more solid.
You only need support under the lower overhangs on stabs and under the LCD, everything else prints great as you would expect. Beware heat soak from retraction on the base, I made the pegs larger which helps but if you keep failing here that's likely your problem. Strings are better than failure, you have been warned.
If you use the parts labeled "with pads" they have breakoff tabs that help hold the parts down and stable. They have a 0.1mm separation gap so they should snap off relatively clean and not leave an exposed infill pattern. On the top and base you may need to hot glue or CA glue these to your bed to get adequate adhesion, especially with PETG. Beware, doing such things can destroy print beds, particularly Borosilicate glass. There's more tips on how I printed these in the Geekhack thread at the top of the page. I did not use a heated bed.
VERY VERY important!!
The base, and pcb need to be printed 90 degrees from the rest of the parts. The reason for this is printer skew. You may think your printer's X and Y axis are a perfect 90 degrees but have you ever actually tested and verified it over long distance? Two 30mm parts fitting together is a lot different than two parts ten times that size fitting together. I loosened the tolerances to help but we're talking tenths of a mm across 300mm span, this is particularly an issue for CoreXy where the belts can twist the carriage.
Assembly
Build the pcb, if you look one pic shows it with stubs hanging, I did this using the diode legs and solid core cat5 cable so it's stiff. From this you can solder jumpers from here to the Teensy. A few Teeny I/O pads line up with the collums, use those when you can.
The pcb should lay in the base flush, or very little sticking up, /25mm or so, if it sticks up more than that, like the thickness of a wire it means it's not sitting flush against the base. You need it to push down all the way in order to support the hot swaps.
LCD presses in from under then the lcd support bolts in holding it up, beware wiring.The little C shaped clip labeled USB support sits under the LCD and lcd support and clamps down the usb breakout board. alternatively you could just hot glue the breakout board in place or just leave it without anythin, it has very little wiggle room regardless. Top and base sandwich the pcb, use the #2 screws around the perimeter.
Trim is inserted from the top, and screwed in from below using #2 screws and this must be done before you install the foot which is done last.
Assembly Tips
Whatever you wire from the Teensy to the USB breakout, beware, some companies swap the wire color codes.
Insert small hot swap end first.
Do NOT push on the metal, if you need to exert any force on the swaps, push against plastic. If you damage a metal clip, toss that swap, don't try and use it. Swap sockets are cheaper than switches, not to mention desoldering and dealing with wiring. You may be able to bend it back but these already have a limited lifespan and you damaged it, how long will it last now? If you insist on using it for instance you have no spares, put it on left control, or any bottom row keys as these will be the easiest to replace later.
Soldering
The hot swap are not pre-tinned on the flat tops where we will be soldering, technically we're soldering to the opposite side they intended. Do a small pre-tin, I HIGHLY recommend getting a tiny brush (trim it down to really small) and apply soldering paste. Using Rosin core solder works, but it's very easy to damage a socket. Beware getting too much solder, you can get extra on the outside ends, but if you get any solder on the inside contacts the hot swap is ruined. Expect to ruin a couple, the solder flux helps a lot by allowing less to do the job but will probably still ruin one or two. Seriously this helped a TON.
Solder the columns first then the diodes, it makes it easier to run, I did it in reverse and it created some issues. Wire the whole thing as stubs as shown in the pcb pic, then attach jumpers from the controller to the stubs this way you keep it all as tight as possible.
Bending Diodes, on the negative side leave 2mm clearance then bend 90 degrees. On the positive side bend the lead immediately out of the diode until it intersects the other lead at a 45 degree angle. If you need wiring to go from one diode to another, you can use the legs you cut off from others as jumpers Don't worry if each diode looks bad individually when starting, as a group they look good by the time you get a few soldered.
Don't start with the top row, it needs to be tucked in tight and you want to practice bending the others first.
It's plastic, if something gets in your way, melt it and make some room. Just beware the pegs from the base, if you intrude on those you will need to alter them as well. Try and keep things flush as there is no room to spare between parts. This is why this is such a challenging project.
If stabs will not go in, clean up underside support, space bar is especially fickle.
If you do break off a few small bits of the top plate, it will likely be fine.
Screws
The M5 holes for the foot are threaded, the rest are not.
You can run a tap through the M5 but it's not necessary, just put the bolts/screws in a thread or two then hit them with a lighter (use the blue part of the flame), when it starts to sag or lean, screw it, then allow it to cool. Do this during a prefit without the mating art or you may melt them together. A lighter works better to create threads than a tap for smaller screws in PLA or PETG, this can also be used to repair threads.
The screws for the housing are #2 screws you can get at any hardware store but any small screw will work. Beware the pencil trim (grooved) if you use #2 it's easy to poke out the tips, I recommend trimming off a mm or so off the tips. Not necessary if you use the flat trim.
I recommend using the heated screws to create threads on all the parts prior to final assembly to make it easier and ensure you don't melt things together.