Analog Keyboard Technology
The capabilities of computer keyboards have not changed significantly over the last few decades, yet keyboards are ubiquitous in offices and homes. New functionality could be added to them if it was possible for software to register how far down key switches are pressed instead of sensing only a single actuation point. Alltrons has made a functioning prototype that is capable of this by using inductive sensors. This a cost effective and scalable method that has not been implemented in a keyboard as of yet.
How can ordinary keyswitches be analog?
Instead of modifying existing mechanical keyswitches or creating a new type of mechanical switch, we were able to make this technology work with unmodified mechanical keyswitches from the Cherry MX series and similar switches from competing manufacturers (Gateron and Kaihua Electronics).
Our advantage is that only a simple modification to the PCB of a keyboard is required to make it analog. This is cheap and does not require a lot of R&D for already existing products to implement.
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Beneath each keyswitch, we place an inductive pressure sensor. Instead of sensing the pressure you put on a keyswitch, this device senses the amount of metal that comes close to this. The further you press a keyswitch down, the more the spring inside will be depressed. Since there is no actual movement or force exercised between the keyswitches and sensors, the measurements steady and trustworthy.
Development Kit / Proof-of-Concept
The proof-of-concept for our technology consists of a pcb with eight keyswitches with an inductive pressure-sensitive sensor below.
To limit the magnetic field of this keypad, we added a case made from a metal sheet.
By making use of hot-swappable sockets for the MX style keyswitches, we ensured that this development kit could be assembled and disassembled without the need of any tools. As can be seen in the picture, we made use of different keyswitches from multiple manufacturers.
#2: Toolless Assembly
The development kit is assembled by sliding the PCB inside the C-shaped metal plate. Both the holes in the PCB and the feet of the device are threaded. This means that the PCB can easily be secured on its location by tighting both the rubber feet and PCB down with the metal plate inbetween.
The hot-swappable sockets can be seen on the bottom of the PCB. The inductive sensors are in this current version of the development kit only located at the top-side of the PCB.
#3: Modular Design
The inductive pressure-sensitive sensors are printed on a seperate FPC (flexible printed circuit board) which is secured to the main PCB using specially designed connectors.
These FPCs are actually not required to make the inductive sensors work, the coils drawn in these ultra thin circuit boards could be part of the main PCB as well. For this reason, we will work on a revision of our initial design before we start selling this product.
The Cherry MX footprint is copied by many manufacturers, such as Kaihua and Gateron. This is super cool, since it means that all these different switches could be used in this analog development kit.
We found out that some switches give us a larger measurement range than others. Switches that are most similar to the internals of an original Cherry MX switch seem to be working better than the boxspring style switches.
#5: Dev-kit or MacroPad?
This is what an assembled development kit looks like! As you can see, it looks more like a keypad or macropad than an actual development kit. We even tried multiple different finishes, such as powder coating which (in our opinion) looks best. The prototype seen on this page currently has a brushed finish.
The result is not just a cool macropad that only has the normal binary functionality of keyswitches. Instead, it measures full range analog input without making a single change to the mechanical switches. In addition, you can always re-assemble it with other switches to your liking without the need of a single tool!
We are still working on the software side of this development kit. Not only do we need to output the analog data to your computer, we also need to remove noise. One of the cool features we would love to talk about more is our filtering algorithm for EMI (electro magnetic interference). To be continued ...
What is next?
We are currently working on a revision of the development kit, which we plan to start selling soon for people to evaluate our new technology.
- USB-C connector
- ARM Cortex M4 chip
- four RGB indicator Leds
- Embedded audio speaker
- two extra push-buttons on each side
- Pressure sensors made part of the PCB
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We have a special webpage dedicated to this development kit which you can find here. We hope to get this little device in your hands as soon as possible.