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Prototype 3D printable lever steno machine.

Part List

• 24x Hall effect sensor: AH49ENTR
• 3x 8:1 Muxes: CD4051BE
• 1x Microcontroller: Seeed Studio RP2040
• 76x Magnets: 5mm x 2mm
• 1x Axle: 5mm x 185mm

PCB

KiCad files for the PCB are in PCB.

AH49ENTR and CD4051BE footprints from DigiKey. RP2040 footprints from Seeed Studio.

3D Printed Parts

machine.3mf contains the assembly with all the parts to be 3D printed.

Firmware

Firmware was written in Arduino and is in firmware.ino.

On first boot, the machine enters calibration mode. Press each key fully down to calibrate the sensor, once all keys have been calibrated the machine will begin to send keypresses.

Assembly

Solder the components onto the PCB. It fits around the second row of pillars in the case.

The "keycaps" for the asterisk and pinky keys are printed separate and can be fit onto the corresponding levers.

Each lever has a magnet hole below the key which is used for sensing. The magnet in the hole on the side should attract to the corresponding magnet hole in the case.

The escapement has 10 magnet holes in the bottom which pair up to the 10 holes in the case, as well as 2 more holes on the side. I learned this was very overkill. I only left 2 pairs of the bottom magnets in. The magnets in the escapement should be repelling the ones in the case.

After all magnets are in, place the escapement and keys in the case and thread the axle through.

Current issues/limitations

• Magnets are stronger than I'd like, makes the escapement mechanism not all that effective. Could either switch to smaller magnets or come up with some system for adjustable strength?
• Key travel on top row is much less than the vowels (though is this just how it is on lever machines?)
• PCB needs to be better positioned and secured
• Axle is not actually attached in the machine at all
• Haven't implemented any actual steno protocols in the firmware. Since I couldn't get Arduino NKRO to work, it only sends the keys on stroke release.