Isomorphic Piano Keyboard Is Button Madness

[nikescar] sent in a link to a huge isomorphic MIDI keyboard. We might have missed it the first time around, but that doesn’t diminish such a great looking project.

According to the project page, this humongous keyboard is the work people at Louisville Soundbuilders’ efforts to clone the AXiS-64 MIDI controller. Instead of looking like a ‘normal’ piano keyboard, this isomorphic keyboard puts notes in a hexagonal pattern. This keyboard layout is very useful – fingerings for chords are the same across all keys – but these keyboard layouts are fairly rare and MIDI controllers are expensive as a result.

To make the keyboard in the video velocity sensitive, there are two layers of PCBs. The top layer uses Cherry key switches, while the bottom PCB is an array of tact switches. Measuring the time between the top and bottom key presses gives the on board microcontroller velocity information that is converted to MIDI notes. This setup has a few downsides, namely the huge amount of switches, components, and pins needed for two keyboard matrices.

The project page hasn’t been updated for a few months, so we’re pretty curious about the current status of this build. If any of the Louisville Soundbuilders have an update on this project, send it on in.

15 thoughts on “Isomorphic Piano Keyboard Is Button Madness

  1. Those are seriously a lot of fun to play. Even without musical theory training, you can play certain rows/patterns on the keyboard and they will all fall within a scale. Easily the fastest way to come up with complex musical melodies I have ever used.

  2. You would think some sort of dual position switch would make the over all layout simple. Instead of having 2 seperate push switches you could use a single switch with multiple position points. This way you only need on ground connection and a single switch to do the same job.

    1. I’ve been searching for just such a switch. Know of any? I could probably fabricate my own, given time, but that would blow up the cost.

      I’m horribly rusty on electronics, but I thought maybe a hall effect sensor with two Schmidt trigger circuits (set to different thresholds) would work even better. Giving you the ability to separately work on the feel of the key and the reliability of no mechanical switches… at the cost of power and circuit complexity.

      I’d love to buy a pair of Axis-49s, only they’re hideously expensive and have only the most basic of MIDI functions. I’d love to build a pair using this or a similar idea with a Teensy++ driving it. Add some dials and wheels, some basic programming. What’s not to like?

    2. That’s a good thought Nelson! Someone else suggested that about a month ago, but as we’re still prototyping v1 we have tried this type of switch.

      I’d love to know if anyone has tried a similar dual press switch and what the tactile feel is.

      The big design concern when this was first being designed, was a tactile feel for the key presses. Cherry switches seem ideal since they were mechanically designed for finger presses anyway. It was the best option outside of more advanced fabrication of a silicon keyboard membrane… which was outside the scope of what we can reliably do DIY with no experience. At least for now..

      1. The main problem with the Digikey switch is the life expectancy, which is 10,000 cycles. If you played any key more that 27 times a day, it would be expected to fail in less than a year. If you played eighth notes at 100 bpm, these would surpass that after 50 minutes. The Cherry switches life expectancy is 50,000,000 cycles.
        (Same problems for the Cherry switches work out to 136,986 per day for the first and 173 days for the last.)

    3. Despite the lack of updates, there has been lots of progress on case and key design for this keyboard. I’ll get some updates written up tonight at our meeting and share them here.

      Also any folks reading this in the Louisville area that are interested, our Soundbuilders meeting is tonight at 8pm at LVL1 Hackerspace. You can see this keyboard in progress and other cool musical creations. All are welcome; bring something to show off or work on.

    1. You probably seen the photo here previously, but if you read the post you shouldn’t be asking if it’s a dupe. A follow up just like the full auto AA shooter article yesterday was a follow up.

  3. Same concept as any chromatic accordion (mot the piano style ones commonly seen). Been in use for decades, but mostly in Europe. Been trying to find an affordable one for years to no avail. Look up the video “Kid Shreds on Accordion” to see one in action. He blazes some Vivaldi.

  4. What about 3D printing both the silicone membrane and the hard matrix that holds the buttons. Seems that silicone would be simple to extrude and build up, like fake body parts.
    There are no replacements for the rubber contacts in many synths more than 10 years old. There are some thin self sticking contacts from 3M but some of these rubber things shred apart. Seems like an area to exploit, these just drop in on a cleaned base for a repair.

    1. This is an interesting idea. I’ve never seen a 3D printer capable of directly printing silicon. If such a thing exists, I’d love to know more. Alternatively, you could print a silicon mold on a 3D printer to use to cast silicon parts.

  5. I need find more info on the time delay velocity you have to write code? is it part of the key matrix? I am having trouble finding what i need for my midi bass pedals. Please help.

    1. We’re using some modified example keyboard code from the Midibox project. I’d recommend starting on the Midibox wiki to determine if this will work for your application.

  6. Here is a photo stream with shots of the Isomorphic Keyboard in progress.

    PCBs are mounted on a laser cut wood scaffolding to fit into the case. This isn’t shown in the photos here.

    Case is waterjet cut aluminum, painted black.

    Sides are laser cut acrylic, stacked and cemented together to wrap around the case edges.

    Keys are two parts. A hefty chunk of black acrylic, milled precisely for a snug fit around the cherry switch stems. On top of those are cemented a 1/8″ laser cut acrylic top in 3 different colors, with a raster pass first to add some tactile feel to distinguish between keys without looking.

    I’m still missing a handful of keys and need to finish the control panel design.

    I plan on making a new video once these last pieces are complete to demonstrate the whole thing.

    Thanks everyone for the interest.

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