"PipKey" Bluetooth MIDI Instrument
Description
PipKey is a handheld MIDI instrument that iterates on the concepts displayed in my ‘MagneTrack’ project. It works wirelessly using BLE and a new keystone system for tracking. The goal was to create a highly portable and musically intuitive design that uses a second passive component, the arm slide, to track the position of the all-in-one device as it moves like a cello/guitar up and down the arm. Rather than use magnetic pogo pin connectors, I opted for a smooth yet springy battery connector and a series of conductive PLA ‘keystones’ that create a pattern of connections that can be read by the microcontroller's input pullup as different finger positions. The buttons play notes at that given position and the joystick shifts either up or down an octave. For reference, you can find the previous iteration of the PipKey project, the MagneTrack, over here: https://www.printables.com/model/931106-magnetrack-midi-instrument - - - - - For better text/list formatting, visit this project's Printables page: https://www.printables.com/model/995672-pipkey-bluetooth-midi-instrument - - - - - If you are genuinely considering messing with the PipKey, please contact me for more info. Please also know that the project is not in an entirely secure state (this is a checkpoint, but it's still technically a WIP). The following does not include an assembly/component guide, but I'd be happy to share more information about the project. Materials: PLA or PETG for everything (PETG is recommended for the buttons) Conductive PLA Solid-core wire ½ Breadboard Various M3 Screws/Nuts Various M2 Screws/Nuts Adafruit Feather 32U4 Bluetooth Spring compression contact battery connector (https://www.aliexpress.us/item/3256805371942024.html?spm=a2g0o.order_list.order_list_main.23.7f561802mBhhgB&gatewayAdapt=glo2usa) Hot glue -Soldering onto the battery connector can be tricky. Use hot glue on the flattened wires afterward. I've included a jig. No images of this, sorry. 4x Kailh Choc keys (plug-shaped top) PSP Joystick 40mm Stretchy fabric -2x segments for securing the rail to your arm -1x 20mm segment (cut in half) for the back of the main body 3x 14mm Magnetic Snaps 1x On/off switch (SS12F15-G5) 2-pin JST connector 3.7v Lipon battery (802030) 6mm HSS Rod 150mm 2x 10x3mm Cyldinerical Magnets -For keystone-positioning on Main body 12x 6x3mm Cylindrical Magnets -8 for use as keystone-position magnets, 4 for use in gripping the metal rod. 5x 30x10x3mm Rectangular Magnets -Technically optional, but supposedly helpful for better battery connector contact -The ones I received were closer to 9.8x29x2.8mm for some reason and the model reflects this design… Notes: Everything is printed at 0.2mm layer height. Print all the keystones at 95% X and Y proportions. At one point, the PipKey supported the use of a simple vibration motor for haptic feedback. However, the motor was found to be too slow to react to most movements. The code still supports the feature, but the features on Main.3mf have been removed to keep things simpler. Perhaps an LRA will be used instead of that sluggish ERM in the future. -Haptic feedback is now sort of provided by the 6mm magnets on the Slide interacting with the 10mm magnets on the Main. The code requires a BluefruitConfig.h file to work. Visit this guide on how to make the Adafruit Feather 32U4 BLE work on Android (with Multisynth): https://www.phippselectronics.com/make-a-midi-controller-with-adafruit-32u4-bluefruit-le/ Room for Improvement: The battery connecter should be completely flush with the bottom of Main to provide as much pressure as possible against the conductive keystone elements. Conductive PLA is convenient for making shapes but I don't believe it's as precise as perhaps a PCB with copper pads would be. (Conductive PLA has a high resistance, but it doesn't affect the internal resistance of input_pullup. Or at least I think it doesn't) The code is still operating in MagneTrack's set of fours instead of more typical finger positions. More testing needs to be done regarding the transition between each keystone and what sort of signals it creates. I'm finding the joystick to not be particularly helpful. Perhaps it could be replaced by a fifth button. -Shifting/effects could be done using a Wii Nunchunk in the right hand.
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