In this post I will try to recall which parts I bought and which I really needed as well as how much time I spend on designing, programming, testing, soldering, drilling, grinding, sawing, wiring and gluing the keyboard. I will begin with the parts that are now integrated in the final – may it be prototypical – version of “TheTasTaTur Mark1”, ordered by expensiveness starting with the most expensive in sum:
- Cherry ML key switches. Originally I ordered 80 pieces. Later I ordered a few (20) more, because I broke some while hunting down the tension bug. The price for each is around 90 cents. In the end there are 79 usable key switches integrated. This sums up to around: 70€.
- Two Arduino Uno for 26€ each: 52€ in total.
- 12 AAA Sanyo Eneloop, to always have a charged set available and two chargers, roughly 45€ in total.
- One BlueSmirf HID: 36,50€.
- 5 sheets of indo ply wood. 3,30€ each, sums up to: 16,50€.
- Three TriPad Stripboards for 3,50€ each: 10,50€ in total.
- Solder, different color wire, glue: roughly 10€.
- Wooden strips of different dimensions and wood type around 9€ in sum.
- As I learned later an unnecessary 5V boost regulator (but it is still integrated): 5€.
- A 4mm force sensing resistor: 5€.
- Thumb slide joystick: 3€.
- Around 100 diodes (I can’t remember exactly but I guess this ones) for the price of 2 cents each: 2€.
- Around twenty 10k resistors for 10 cents each: 2€.
- A power switch, extracted from a toy: 0€.
- Switches for the mouse buttons, extracted from another toy: 0€.
- OpAmp (LMV358) extracted from our old burglar alarm: 0€.
- An old USB cable: 0€.
- A potentiometer extracted somewhere I can’t recall: 0€.
- Screws I already had somewhere: 0€.
If I haven’t missed anything that’s a total of around 270€. If I would have been able to build the keyboard without any trespasses, I already had all tools and I ignore the labor costs I saved around 90€ compared to buying the Kinesis Advantage Pro. But that is naive fallacy. Alone the parts that are now waiting in my spare parts cabin for a new project: 4 LiPos, 2 LiPo charge circuits, another 5V boost regulator, RF sender and receiver, another BlueSmirf, 2 Analog/Digital MUXs … maybe more, would rise the costs above the 360€ deadline. But when it comes to labor costs the comparison gets totally pointless.
Soldering the keyboard matrix took around 16 hours effort. The case around eight hours. Creating the key caps was the hardest and most time consuming part. I sat for three weeks almost every evening for three hours in our basement. I first glued two sheets of ply wood together to make the key caps a little thicker. I then glued a printed out stencil of the keys on the ply wood and sawed the keys following the stencil lines. The most difficult part was to properly attach the key caps to the key switches. I found some metal pins (they were too long, so I had first to shorten them) that fitted tightly in the openings of the key switches. I drilled four holes in every would-be-key-cap (remember the stencils) and glued the metal pins in. Unfortunately this connector is a real weak point. Because it was nearly impossible to get the distances right. So some key caps are quite loose and fall off when you turn the keyboard up side down. But hey, why should I turn it up side down … aargh, every time I have to change the batteries … Painting the letters and varnishing the case and the keys took me the final eight hours of manual labor.
Coming to the brain work. Planning and research took around 16 hours effort. The programming, bug fixing and testing around 50 hours effort in total. I’m not able to separate the effort spent by feature. I know that the bluetooth low level communication and the radio communication between the keyboard parts were bigger points as well as the late integration of the mouse behavior. I took an incremental approach and switched back and forth from brain to manual work. From creating the case and wiring the circuit to program and test it.
I started in December and “finished” in March. And even when I spent a lot of time with this project, alone the things I learned and the good feeling of having created a keyboard which is still fun to use are priceless. Somewhat geekish … I have to thank my wife for tolerating this.