Project code, CAD files, and build guide
Teensycorder - A MIDI baroque recorder/blockflute with easy capacitive touch input, and breath control via differential pressure sensor.
Goals of this project:
Improve upon the Teensycorder Prototype #4 by implementing breath sensing via a differential pressure sensor.
In an effort to keep this project as inexpensive as possible, I initially planned to replace the arcade button used to detect "breath" input on prototype #4 by utilizing the one remaining touch pin I had available as a tongue sensor at the tip of the mouthpiece, however this was a bit more disgusting than anticipated, and beyond that the effect of saliva on capacitance is enough to make accurate detection difficult.
Especially with the threat of communicable disease lately, an interchangeable mouthpiece was a must, and with it came the added expense of a pressure sensor. That said, the cost of the MPXV7002DP sensor I used has tripled since I purchased in early-2020. I'm leaving the Amazon link as originally purchased, but it may be worth searching for compatible parts on Digi-Key, Mouser, or elsewhere.
The remaining touch pin was instead used as a "bell key" to add the additional notes made possible by covering the bell hole. Having only ever played cheap plastic recorders, it's neat having access to the full 2.5 octave range.
Shopping list used for this build:
Note: In total, parts cost approximately $60 USD for this project without modifications, as built in 2020.
1 x Teensy 3.2 or other Arduino compatible micro-controller with sufficient I/O pins
9 x 6mm x 6mm x 10mm Momentary Push Buttons
12 x Brass Plated Paper Fasteners (1/2" shank, 8mm head)
1 x MPXV7002DP Differential Pressure Sensor
Panel Mount Jack:
1 x Micro USB 5-pin Male to USB Type B 2.0 Female Extension Panel Mount Jack
1 x Kit 22 AWG Multicolor Wire
1 x Spool PLA Filament 1.75mm - Black
1 x Spool PLA Filament 1.75mm - White
All information in this guide is provided "as is", with no guarantee of completeness, accuracy, timeliness or of the results obtained from the use of this information, and without warranty of any kind, express or implied, including, but not limited to warranties of performance, merchantability and fitness for a particular purpose.
By following this guide, you agree to be responsible for any decision made or action taken in reliance on the information given, or for any consequential, special or similar damages, even if advised of the possibility of such damages.
Print all 7 case pieces in filament and colors of your choice:
Pressure sensor housing
USB port bell cover
Touch Pin Installation:
Insert brass fasteners through the touch button slots with the rounded end on the outside of the instrument.
Measure, cut and strip wires to length to connect each of the 12 fastener slots to the location in neck piece where the microcontroller will be housed.
Solder one end of each wire to the back of each of the 12 fasteners.
Hot glue all of the fasteners securely in place on the inside.
Momentary Push Button Installation:
Using a drill and bit with a slightly larger diameter than your push button stem, round out each of the push button holes to ensure they are round, and that friction will not interfere with their use. Place a push button into each of the 9 button housings in the rear body.
Measure, cut and strip wires to length to connect each of the 9 push buttons to the location in the neck piece where the microcontroller will be housed. Solder one end of each wire to the top-outside lug of each push button.
Measure, cut and strip wires to connect the bottom-inside lug of each button together into a common ground, and solder each of the bottom-inside lugs together.
Measure, cut and strip a wire from one the common ground lugs to the location in the neck piece where the microcontroller will be housed, and solder to the common ground lug.
Hot glue all of the buttons securely in place on the inside.
Remove the bottom stem of the pressure sensor with a flush cutters, being careful to cut cleanly and not obstruct the opening.
Insert the pressure sensor into the 3D printed housing, pushing the top stem through the hole in the housing.
Seal the area around the stem and hole using a small amount of epoxy, UV curing resin, or other water-tight sealant to prevent moist air from flowing into the electronics during use. Again, be careful not to obstruct the stem opening.
Flood the space around the body of the differential pressure sensor with hot-glue to hold it in place and make sure that it will not shift and crack the seal.
Once the moisture seal is solid, snip the remaining end of the stem so that it sits flush with the front of the housing.
Wiring to the Teensy 3.2:
Note: Left/right perspective is from looking at the face of the instrument with the button on it.
Touch Pins Front:
Touch Pins Rear:
Upper Set of Push Buttons:
Lower Set of Push Buttons:
Note: Don't forget to slide the neck piece over the wires before soldering the pressure sensor wires to the Teensy. It may be beneficial to snip these in the center, and connect with pin/socket connectors or small wire-nuts to allow for easier take-apart and maintenance later.
USB Panel Mount:
Attach the USB panel mount to the bell cover, fold the cord to fit inside the body of the instrument, and connect to the USB port of the Teensy.
Once everything is in place, gently fold the wires so that everything fits inside the body when closed.
Cut a strip of tape, and wrap one layer around both the top and bottom ends of the body, and another around the bottom of the mouth piece, folding a bit over the edge. This should hold the halves together, and provide enough friction to keep the pieces in place without glue, allowing for adjustments later. If you prefer a more secure fit, you can superglue the pieces in place later.
Gently press the neck piece, and the bell cover in place.
Gently press the mouthpiece in place into the neck.
Superglue the thumb rest into the slot on the back body.
Press fit the interchangeable mouthpiece over the pressure sensor housing.
If you've made it this far, congratulations!