Hidden Touch ID for Apple Magic Trackpad

Touch ID is super convienient when using macOS, but it is restricted to Apple keyboards and those are not really something I enjoy or want to keep on my desk. SnazzyLabs' standalone Touch ID module inspired me to build something similar, yet I wanted to avoid additional clutter. So I set out to seamlessly attatch the Touch ID button to something that's always sitting on my desk: Apple's Magic Trackpad. The product is a tenting stand that hides most hardware below the trackpad. 

Features: 

• Touch ID sensor is angled down at the back to stay out of sight 
• sensor button retains its clickability and is comfortable to reach
• hardware is precisely layed out and held in place within the model
• <5 deg added tenting angle
• edges are flush with the trackpad on top for minimum added bulk

Required hardware:

Apple Magic Keyboard with Touch ID 60% version without numeric keypad. 

The PCB of the larger keyboard with numeric keypad will not fit. Compatible with both Lightning & USB-C versions of the keyboard (special thanks to @ccadigan90 for providing the measurements to make this possible!). 

You will not be able to reassemble the Magic Keyboard properly! Please avoid using new keyboards for this project. Check your marketplace of choice for partly damaged keyboards (missing keys and such) to save money and help reduce electronic trash at the same time.

Disassemble to get the following individual parts:
(See this guide by Khaos Tian,  Jeff Geerling's video and Thomas Hartmann's video for tips on the disassembly process.)

• PCB, 

• Li-ion battery, 
• Touch-ID button (the glued-on white Keycap/Trim can stay attached if you do not plan to replace it with e.g. a colorful print. It is very delicate and breaks easily.),
• metal spring plate, 
• Lightning or USB-C port flex cable, 
• rubber feet (not shown in photo), 
• 4 screws from button assembly, 3 from PCB and any other 4 from the keyboard.

• optional: rubber mounted metal cylinder from original button assembly for the second mouting plate

   

Choosing the correct model for your print

There are 4 variants in total. Which one is right for you depends on your specific hardware revision of both the Magic Trackpad and the Magic Keyboard with Touch ID.

First you need to determine the version of your Magic Trackpad. As shown in the photo, Trackpad 3 (released 2021) has a larger fillet radius compared to Trackpad 2.  This becomes more obvious when looking at the space between the device's edge and its rubber feet. Also the bottom side on the Trackpad 2 I had at hand was shiny whereas the Trackpad 3 bottom plate is matte.

Having determined that, next you can choose the correct files to print based on the connector of your Magic Keyboard, which will either have a Lightning or USB-C connector.

Printing recommendation:

• Most top surfaces are slightly slanted. Choose a very small layer height (0.08-0.1).
• Tolerances were chosen pretty small. Using “silk” filament can cause issues here due to its foaming properties. Usage of more dimensionally stable filaments is recommended.
• Use the Arachne wall generator.
• ideally the clickplate should be printed on a smooth build plate

Assembly

These awesome guys provided additional information on the process:

• build log by Jordan Elver, which provides way more details plus some crisp photos for every assembly step. 
• YT video [German] by Thomas Hartmann, who shares his entire build process of a mirrored print in 4k res, starting from keyboard disassembly.

You can follow the assembly process in order of the gallery photos starting at photo 5:

1. Attatch the rubber feet to the tenting base. Mine still had the original glue on them, which adheres well enough to PLA.
2. Slot the PCB and connector into place. Use the original screws to secure the PCB in place. The screws will act self-tapping when applying a little bit of pressure while screwing them in. Be careful, as they are easily made useless by overtightening them. 
3. Choose your mounting plate: 
   1. the simple flat one will do just fine. 

   2. the second option will give a slightly dampened, lower frequency clicking sound to the button. It has a recess for the optional gasket mounted metal cylinder, which simply has to be inserted into the cutout before slotting in the Sensor/button assembly. In case the mounting plate's overhang has not printed cleanly, gently scrape off some material with a flathead screwdriver to make it somewhat even

4. Slot the Touch ID sensor/button into the mounting plate - correct orientation is guided by the rounded corner and cable cutout. Insert the metal spring plate from the bottom (silver corners should be visible) and screw everything in place.
5. Slot the long flex cable through the hole in the sensor's mounting place and orient it such that it later allows for the 90° bend. Avoid twisting either end of this fragile cable independently
6. Gently try to press the mounting plate into its slot. If it does not click into place easily, avoid excessive force on the button, and instead use a flathead screwdriver to apply force on the mounting plate directly (you might need to remove the key trim to do that).
7. Route the flex cable underneath the lid rest above the pcb and connect it.
8. Insert the wedge to secure the Lightning/USB-C connector in place.
9. Connect the battery to the PCB and slot it into the recess.

10. Insert the lid and secure it in place using 4 screws. Again be careful to not overtighten them.

    Congrats, you did it!