DIY digital piano: a janko variant

Mike Filip · 2024-12-27T17:38:32+00:00

Hello everyone; Ive gotten into a bit of a rabbit hole last year that started with learning chords and improvisation, continued to music theory and isomorphic keyboards, and spiraled out of control into janko keyboard layout and a DIY project for a fully custom digital piano with realistic (or as realistic as I can get) action. Gotten to the point I have a prototype action (with sensors and everything) working, so I started posting some progress reports and putting together youtube videos about the project. Some of the posts here (CyberGene's original designs and the stem-piano) were exceptionally useful, though I ended up going with something different for the electronics. I cant exactly post images here yet, but I wanted to start this post to talk about the design as well as post updates, along with the following locations: Facebook Group: Its a janko piano group, but due to the nature of isomorphic layouts Im pretty sure nearly everyone is a bit of a DIYer here. Have also been lurking in the background the past year and only recently started posting about the progress. Its got some pictures of the design right now, plus a couple videos. Youtube Channel: I just recently put it together, so at the moment it just has a single 'promo' clip that I will be using as the opening or intro to the other videos; but I plan to start adding the actual videos to the channel after new years. Already got a couple clips talking about the project, janko layout, and the piano action; just need to finish editing them. About the design (Janko Layout) So I am a bit of a self-taught pianist, having started playing piano in university when I transitioned to it from guitar (for which I did have a year or so of lessons, though none of it focused on theory). Up until now I relied mostly on learning pieces through muscle memory and 'hearing' when a note sounded wrong in context. Last year I decided to learn music theory so as to be able to learn pieces 'better', which lead to 12TET tuning and isomorphic keyboards. The Janko layout was where I ended up - its an alternative piano layout invented in 1882 with was supposed to be the 'next big thing', so much so that even Franz Liszt thought it would it would take over the piano market… but yea - turns out that switching keyboard layouts isnt easy. Since then there have been several attempts at a similar concept, but obviously nothing can push the piano off its pedestal. PS: quick explanation about isomorphic layouts: the 'big idea' is that on a regular piano (which is non-isomorphic) you have to memorize 6 different positions for each chord - so a C major is all white keys, while D major is white-black-white, and so on. This makes transposing a song (or a piece of a song) difficult as the fingering will be completely different, and makes it less intuitive to play (same shape corresponds to different intervals, so at least personally this meant that as I was memorizing pieces I could remember which keys to press, but not recognize that I was playing an F major arpeggio). With a janko layout (as with all isomorphic keyboards), the 'shape' of a given chord is the same - so if you play a C major and want to play a D major you just have to shift your fingers one key down the keyboard without modifying your hand's shape (C# would be the same shape, but up on a diagonal). For a 'simpler' isomorphic keyboard think about what would happen if you moved the white keys C,D,E into the back row and the black keys C# and D# into the front row (so your 12 key octave will have 6 keys on the front and 6 on the back - here is an example); so a C major would be upper-upper-lower shape, and D major would also be upper-upper-lower (C# would be lower-lower-upper… so not true isomorphic, but instead of 6 shapes you have 2 mirrored shapes - bit easier to remember; the janko is basically this concept just with adding more rows of the same keys so as to make 1 shape instead) About the action (Hickman action) After trying out a bunch of digital pianos in the shop I came away preferring the acoustic actions, so ones like Novus NV10 and similar. Once I started working on the DIY project it seemed only natural to try and incorporate that instead of going with the simple 'weighted hammer' approach. This posed issues, as the janko layout necessitated narrower action (in the acoustic janko layout the piano keys were placed on angled levers to shrink the octave span, but I figured just narrower action parts would be easier), meaning I had to make custom action parts… which would be difficult with the complexity of the Erard double escapement action. Around the time I was starting my design in fusion 360 I came across the hickman action. This offered a much simpler design while retaining the 'realistic grand action feel' that I was chasing, so I pivoted to it instead. This did end up meaning that I had to learn all about key guide pins, center pins, action bushings, and all the rest… So now my workshop is a mess of piano felt + hardware and 3d printed parts + tools. The action did turn out to work beautifully, so I have that going for me at least. About the electronics Initially I took inspiration from CyberGene's work and started working on an 8 key double-optical slit sensor board that would be connected in series with a main board that would scan through each board consecutively to read the sensors, but one thing lead to another and I ended up with each 8-key sensor board having both 2x optical sensors to pick up hammer velocity and a hall-effect magnetic sensor to read the (analog) key position (so 16 optical + 8 magnetic sensors). These sensors would be read by a dedicated STM32 microprocessor that would talk via 2x SPI channels to the boards to the left and right of it, with a single 'controller' board placed at one of the ends that would 'request' key data (with that request being echoed by each board down the line), and the receive the data (once again, echoed by each board back to the controller). The controller would then package that data into a MIDI format, accounting for things such as velocity curves and pedal input. Essentially the sensor boards would be in charge of keeping track of the key states and accurately measuring the velocities with timing down to a couple microseconds, while the controller would just get a 'key press' or 'key release' data every millisecond or so and send it as MIDI to the mini-pc running pianoteq. Current state of the project At the moment I have finished the final design of the 8-key prototype and am printing out the parts needed for a full piano. I have the prototype working with the control board & mini PC running pianoteq, though with only 8 (chromatic) keys Ive only really got the first 5 notes of the A major scale to play with - enough to play the 'beginner' version of ode-to-joy, but not much else. Ive taken the prototype over to a piano technician in the Toronto area, which they marked as being 'quite good, almost feels like an acoustic grand', though we did spend quite a bit of time tuning the letoff mechanism in-shop. As of right now I am mostly taking the time to finish up the videos talking about the project instead of working on the finished build, mainly because I have thoughts of making a 'timelapse' video of it being put together, which means I need to knock out the other videos first… Design files and CADs I have plans to release the fusion 360 files along with the electronic board designs (made in easy eda), though at the moment its all just stored locally on my computer (or at least as 'locally' as fusion 360 and easy-eda with their cloud storage can be). I think I can make them 'publicly viewable', but doing anything like that is just extra work on top of this project so it depends on when I get around to it.

Mike Filip

Posting the video about the hickman action - going to start a new sub-thread focusing on the action, such as 'how does it work', and 'how do the centerpins function' ,etc.

Mike Filip

Posting the video about the parallelogram linkage of the keys. Will just leave it in this thread instead of starting a new one as its not really as complex as the other topics.

In summary, regular pianos feature a simple lever for their keys - which makes playing the same note at constant volume require different amounts of force based on where you play on the key (playing along the back requires ~2x more force and has 1/2 the travel distance than playing along the front). In the Janko piano this is further worsened by the keys being longer, so either the lever needs to be longer as well or the player needs to accept 3x or more difference between the front and back rows.

To solve this a parallelogram linkage is used to ensure that the key has a consistent 10mm of dip throughout the entire key - no matter if you play on the front row or the back row.

PS: just to clarify; the difference in key dip along the length of the key on a classical piano isnt exactly a 'problem' for players - you pretty much never think about pressing 'harder' when playing along the backs of the keys - you just do it subconsciously. However as anyone who played on a cheaper synth keyboards with like 1mm key-dip along the backs of the keys can tell you there are limits here - 2x difference is kind of the sweet spot, and on a Janko keyboard with its longer keys it becomes harder and harder to stay within that sweet spot for all rows - hence the parallelogram approach.

Plus, having consistent key dip is kind of nice in and of itself. Almost like taking off a weight you've been carrying for so long you no longer notice its there.

Mike Filip

Well, time to start covering the actual prototyping and design instead of just the theoretical stuff.

Posting the video about the initial prototype, along with going over it in Fusion 360. As you can imagine I probably printed out enough parts to make 2 prototypes (at least based on weight of plastic) before I felt satisfied with the prototype… or at least until I realized that any further changes would require nearly a complete redesign.

Mike Filip

Time for the electronics (video here). I expect this to be a bit more interesting for those in this forum, and I will be making a new thread for it here.

Mike Filip

Video covering the final prototype that I am going to be using in the full 88 key build is now out. Just got one more video to go talking about the design (will cover the mini PC, MIDI interface, DAC, touchscreen, Pianoteq, etc) before the assembly of the full piano.

RIP

Mike Filip Just got one more video to go talking about the design

Congrats you've got quite far and solved quite a bit of issues on your own along the way. Impressive!

vagfilm

I am always amazed by anyone who can manage a Fusion project with dozens of parts. Congrats.

Mike Filip

Last video about this project (or at least the 'design' portion of it). Going to cover the 'covers' of the piano along with the 'controller' portion (mini PC, DAC, power supplies, VST, etc).

At the moment I am pretty much just working on the actual assembly (already at ~350h in terms of assembly time and probably 50 to 100 more to go), so…

RIP

Wonderful, thanks for the update

Mike Filip

Halfway point for the assembly; got the chassis, covers, and keys all done, so all thats left is the actual action for each of the 88 keys.

Been also working on the control board that will interface between the sensor boards and the rest of the piano (LCD panel, rotary encoder, 2x usb outputs, serial MIDI in/out, 3x pedal unit, 1x pedal unit,… plus 12 buttons and 6 sliders that are going to be left unconnected for now but in the case I decide to expand the front panel of the piano to feature buttons & sliders for stuff like piano selection and reverb control I will then not have to remake and reorder the control board.

RIP

Kudos to you, I'm impressed, especially with how fast you are proceeding!!!

Any chance that you are going to release the "blueprints" (3d step files, or other sources, firmware code etc)? Even privately for a fee? If not (which is totally fine, obviously), do you plan to find a retailer to sell the finished product?

@dore_m and @vagfilm in case you have missed this update!

dore_m

Man, such commitment. Looks like you upgraded your Prusa too.

Mike Filip

dore_m Looks like you upgraded your Prusa too

Yep - did that even before I started this project (or at least before I started printing the prototypes). Enclosure was kind of mandatory for ASA (which I use for the keys), plus highly 'recommended' for PETG (everything else). Besides that I did a bunch of upgrades (including a custom-design 'clicky' style probe to get consistent 1st layers along with the 'silicone' mod to get the print bed as close to flat as possible - both of which were mandatory to get the framework to fit together).

Probably (read: definitely) got more hours of printing done during this project than I had the other 7 or so years I had this printer (got it right when it first came out).

Mike Filip

Been a month, but I finally got to the point I have a proper update!

So - the piano is officially working, though the hammer action (and kind of the entire Hickman action actually) is still taking up space on my assembly bench. I had to hack apart my sensor board firmware to make the magnetic sensors pull double duty for note-on (with velocity) events as well as their official job of note-off events seeing as how without the hammers there is nothing to trigger the optical sensors. Still, this means I can actually start practicing on the Janko layout instead of thinking/designing/planning/printing/…working on it.

Finished up the main control board too - kind of funny how it took me over 3 months to get the initial sensor boards planned out and ordered, but the control board (which is ~2-3x more complicated) was finished up in under a month. Even better - both the sensor board and the control board worked perfectly on the first try, so no need to re-design and re-order! I will probably at some point invest in a proper oscilloscope and optimize the communication lines; I seem to get only 4Mbits/s SPI speeds while 9 should be possible for the chips; still - there hasnt been any communication breakdowns in the past 3 days Ive been running it so it should be in a good state as is.

Well, I will leave just 2 more video links for the two piano pieces I figured out in the 3 days I had to practice since getting the piano operational if anyone is interested:

RIP

Mike Filip So - the piano is officially working,

Wow, huge work and fantastic success! Hats off to you!

If you are not releasing your blueprints, do you plan to sell this, for parts or as a whole?
In any case, congrats and looking forward to how you'll learn music with it!

RIP

Also @Mike Filip have you considered participating at https://midi.org/innovation-awards ? I think you have good chances!

gzpiano

Impressive!

Mike Filip

RIP
Interesting competition. Might not completely mesh with what I am doing (after all, I am aiming towards more of a classical piano than an innovative synthesizer keyboard), but its not like I loose anything from submitting.

Deadline seems to be may 30th which is a bit tight, but even if I dont finish the assembly its not like I cant submit what I have and see what happens.

Thanks for bringing this up!

Mike Filip

Well, here is the video for the control board schematic. Think it should be a bit more interesting to those in this forum as opposed to the 'Janko layout' parts.

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