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[BUILD] Magic Keyboard 2 but mechanical

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Limentic:
Hey folks,

I've been quite occupied this month, but I still managed to squeeze in some time to work on this project :)

Taking a break from the electronics side, especially the Touch ID part where I haven't quite figured out how to reverse engineer the ribbon, I've mostly wrapped up the CAD work, and it was crucial to kick off the CAD anyway.

How am I supposed to design the final circuit board if I don't know the size and shape? And where I need to put the connector to line up with the one on the Apple motherboard? What shape and size should the touch ID ribbon be, etc.
Basically, it was needed to figure out how the components will be laid out in the case.

Given my unconventional keyboard layout, I scoured the internet for hours but couldn't find THE keyboard case I was after. So, I took matters into my own hands, which makes more sense for my project anyway.

I wanted a case that kinda looked like the original Magic Keyboard, and that's exactly what I've done.
I've replicated the lighting port centered on the back, the angle of the front plane where the keys are, and the overall shape and look. Obviously, I redid everything from scratch since my keyboard is a bit larger than the original.

Here are some pictures of the 3D model of the case:




As you can see, I added a battery holder for the Magic Keyboard battery at the bottom.

The battery will be stuck in place by some iPhone battery strips. Those strips are everywhere, dirt cheap, and they do the job. No need to complicate things with extra pieces of plastic or screws.

The lighting plug will be held in place with hot glue and a snug fit. It's the only way I found to keep it in place because the original method involves two little tubes that go through the connector. Those are tapped, and the connector is screwed into those tubes. It's impossible to find a brass insert that small that could be inserted into a 3D printed plastic tube with such thin walls that passes through the lightning plug without destroying the hole for the inserts, so hot glue it is.

However, the Apple motherboard will be held in place by screws and brass inserts :)

Here's what the original mounting contraption for the lighting plug looks like:


My PCB will be mounted on top, with brass inserts and screws as well, essentially closing the keyboard case.

Here's what the finished case looks like with the PCB mounted on top:


Now, let's talk about the Touch ID keycap!

This keycap is going to be printed in two parts.

The first one is the bottom part, which is the structural part of the keycap. Where the keycap stem is, and where the Touch ID sensor and its frame will be mounted and secured.



The little squared hole is for the ribbon.




The second part is the top part, which is actually just a cover for the metallic frame of the touch ID sensor. It will be held in place with some double-sided tape to the frame of the Touch ID sensor. It's actually what Apple does with the original keycap :rolleyes:.




Here's the final result:



This keycap is going to be printed out of resin or nylon because of the thinness of the top part. It's way too small to be printed with FDM. However, the main case is going to be printed out using FDM (ABS or PLA, I don't know yet), because it's much cheaper for larger pieces.

I don't have access to a 3D printer, so I'll be using a 3D printing service. I'll probably use PCBWay, since I will be ordering the PCBs from them anyway.

Here's the final result of the keyboard case with the PCB and the Touch ID key:



And here's the PCB on KiCad:



I still need to route the traces, but I'm waiting for the ribbon to be reverse-engineered before I do that.

That's it for today; I hope you enjoyed this update! Stay tuned for the next one.

Cheers!

Limentic:
Hi guys,

Today, a quick update on the project.

I've been able to reverse engineer the ribbon cable of the Touch ID sensor!
I'm now sure that the button behind the sensor is hooked up directly to the Apple Motherboard, not to the sensor itself.

How I've done it considering how small the pins are?
I've used a microscope camera, spring-loaded needle probes, a multimeter, and a LOT of patience.

A huge shout-out to my local university for letting me use their equipment!
I wouldn't have been able to do it without the equipment they have.

The setup:


As you can see, I taped the ribbon cable to a marble to keep it flat.
I then placed the two ends of the ribbon where the connectors are, close to each other, so I could see and probe them using the needles.


- On the left, the connector to the Apple Motherboard, the Molex 505070-1422
(datasheet https://www.molex.com/pdm_docs/sd/5050701422_sd.pdf)

- On the right, the connector to the Touch ID sensor, the Hirose TF22-16S
(datasheet https://www.hirose.com/fr/product/document?clcode=CL0480-0346-0-00&productname=TF22-16S-0.175SHW(800)&series=TF22&documenttype=2DDrawing&lang=fr&documentid=D169701_en)

To put this picture into perspective, the pitch between two pins on the Hirose connector is 0.35mm (0.0138 inches) and the pad itself is 0.2mm (0.0079 inches) wide.

How did I find where the button was connected?

First, I removed the glue covering the little tiny pads on the Touch ID button.


Then, I probed the pads on the Touch ID button and the pads on the Molex connector to check for a connection between them.
And indeed, there was!

The top pad is connected to the ground and the bottom pad is connected to pin 9 of the Molex connector.

MolexHirose16, 16, LOCKPAD, 1, 326, 16, LOCKPAD, 1, 3324NC546NC7581197101011812913121414, 13, 15
Now that I have everything I need, I can start designing my custom ribbon, route the final PCB and 3D print the firsts prototypes of the case and the keycaps.

Still a lot of work to do, but there is light at the end of the tunnel!

See you next time!

WizMeister:
I registered on this forum to pay respect to your determination! Iím a long time Mac user / software engineer and recently switched to a mechanical keyboard. Touch ID is the reason I have the Magic Keyboard still on my desk.

Would be super awesome to see a ready made kit in the market :) 

Limentic:
Hey man, I really appreciate the support, and your message means a lot to me!

I've already considered putting together a DIY kit for those interested.

However, keep in mind that the project will be open-sourced once it's ready :)
In theory, you could send all the files to PCBWay (not sponsored, but I wouldn't mind, lol) for the PCBs and 3D files.
It might get a bit pricey, and you will end up with 5 PCBs even if you only need one, but you'd still be able to build a keyboard ;)

I'm not against the idea of creating a kit, but I need to assess the level of interest. If only two people are interested, that won't cut it, xD.

Here's a sneak peek for you, at the current state of the project:

ankit:
insanely cool, can't wait to see the finished result

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