Creating the Obelus Kit
The image above shows one of the first built prototypes of the kit. From the beginning, it was designed for easy assembly and modability. The board runs the open source QMK firmware, creating a completely programmable and customizable USB based peripheral. Here it functions as a numpad.
Hand Wiring Prototypes
The Obelus board is an extension of lessons learned working on previous projects. One of the best ways to learn how a keyboard works is to hand-wire one. This project utilized an Arduino clone called a Teensy 2.0 running firmware to act as a keyboard controller. The matrix circuit to serve the key switches is hand-wired in place.
Learning How Circuits Work
Utilizing rough hardware prototyping, I tested circuit designs on breadboards before committing them to PCB (printed circuit board) fabrication. Here, I'm testing a circuit to control brightness of in-switch LEDs, as well as creating music with a pezio speaker borrowed from a gift card. All of these functions are supported by default in the QMK firmware, so building hardware support was a matter of designing to standards.
Creating the Schematics
To be able to speak with PCB fabricators, a design needs to be communicated through standardized file formats. I used Kicad, a free and open source tool for the project. The schematic for the keyboard is shown here.
PCB Layout
After the basic logistics of the schematics are determined, next comes determining where the actual components are located and connected on the PCB itself. Often components exist in libraries, but some custom footprints had to be created to accept some uncommon pieces, such as the pezio speaker. Once all the cad work is done, files for fabrication can be exported for manufacturing.
Printed and Assembled PCB
The final pcb is fully assembled, save for the components students will hand-solder in the workshop. The board is essentially an Arduino clone with some special on-board components which make it function as a keyboard, given the right firmware. All the components are cheap, readily available, and well supported by the QMK firmware. All unused pins on the controller are pulled out and made accessible at the edge of the board so it can be further integrated and used for testing on future projects.
Prototype Testing
Once the first batch of test boards came, these were assembled and tested to make sure everything worked as expected. Here, a caseless board is assembled to test out the in-switch led capabilities.
Case Design
Utilizing SketchUp I created a number of prototypes before a 3D print was made. This case design is created with 3D printing or CNC milling in mind. The large beveled bezel is a nod to the original Apple M0110 mechanical keyboard, a favorite classic design of mine.
Finished Prototype
The finished prototype has a handsome presence on a desk, and is extremely flexible and capable for its size. It's simple enough for a novice to assemble, and, utilizing open source firmware and flexible hardware, creates a great platform for experimentation and hacking.
