The EUCLIDEAN
Build Guide

Looking for the User Guide? Find it here
Looking for the firmware source? Find it here

Circuit boards

The EUCLIDEAN is comprised of 2 boards — an upper board with the pots, encoders, switches and their associated chips (MCP23017s for the switches and encoders, and a CD74HC4067 for the pots), and a lower board with the Teensy 4.0, the Teensy Audio Shield, plus the MIDI I/O and power circuits. The two boards are connected by standard a 20pin cable with 2x10 headers.

Although the boards can simply be stacked vertically, they are designed to fit the Pactec PT-8 enclosure.

Two additional boards function purely as panels — a top panel for the controls and a rear panel for the connections.

Upper circuit

Lower circuit

Upper layout

Lower layout

Bill of materials

Upper board

Lower board

Other
  • 3 x 10K vertical pot, linear, 25mm shaft (tempo, volume and drum volume)
  • 8 x 10K vertical pot with centre detent, linear, 25mm shaft (sequencer step controls)
  • 3 x 24 pulse vertical encoder, 25mm shaft with switch (select, meter and preset controls)
  • 4 x 24 pulse vertical encoder, 25mm shaft w/o switch (general controls)
  • 13 x 3mm red LEDs
  • Optional 0.1uF ceramic capacitor (MUX bypass)
  • 8 PB-86-A1 single LED switches
  • 2 PB-86-A2 double LED switches
  • 4 TS5 9.2*9.2mm Momentary SPST Mini Push Button Tact Switch With LED
  • Adafruit 1.8" Color TFT LCD display with MicroSD Card Breakout - ST7735R
  • 10 pin SIL header for LCD
  • 2 x M2 screws and nuts, 2 x 4mm and 2 x 6mm spacers to mount LCD
  • 2 x 10 pin male header (recommend polarising slot)
I used D shaft rotary controls, with these knobs for the encoders and these for the pots.
  • C1 10uF electrolytic capacitor
  • C5 0.1uF ceramic capacitor
  • C6 10nF ceramic capacitor
  • R32 1K resistor
  • R33, R36 220ohm resistors
  • R34, R37 47ohm resistors
  • D15 1N4148 diode (or similar)
  • OK1 6N138 optoisolator (8 pin DIP)
  • Ferrite bead (I used a Murata BL01RN1A1F1J)
  • 4 x 14 pin SIL headers for teensy and audio shield pins
  • 4 x 14 pin SIL female sockets for teensy and audio shield
  • 3 pin SIL header for audio shield line-out
  • 3 pin SIL female socket for audio shield line-out
  • 2 x 10 pin male header (recommend polarising slot - optional right angle)
  • S1 SPDT right angle PCB mount mini toggle switch
  • PWR_SEL 3 pin header and jumper, or small SPDT switch for internal power selection
  • PCB mount stereo jack socket (RS Components 913-1021)
  • 2 x 5 pin DIN connectors (PCB mount - wide spacing on front two pins)
  • Right-angle through hole PCB mount type A USB connector
  • Right-angle through hole PCB mount type B USB connector
  • Teensy 4.0
  • Teensy Audio Shield 4
(See the layout image for the footprints for the DINs and USB connectors.)
  • 4 x 25mm nylon screws and nuts to attach the control board and main panel
  • 4 x 10mm nylon spacers to separate the control board and main panel
  • 20P cable with 2x10 female connectors to join the boards
  • Pactec PT-8 enclosure (Mouser part 616-82399-501-000)

Building the Lower Board

Follow these steps to construct The EUCLIDEAN lower (microcontroller, audio and I/O) board.

At each stage carefully check continuity according to the schematic, orientation of components, and ensure there are no short circuits.

Components and panel for the lower board
Solder the pin headers to the Teensy and Audio Shield as follows to ensure proper alignment with the rear panel holes when placed in the sockets
Solder the resistors and diode first
Then the other low-profile components
The capacitors and ferrite-bead for the power input circuit
The MIDI, USB and interconnect sockets
Solder the sockets for the Teensy and Teensy Audio Shield, taking care to keep them vertical. Also the power select header to choose between power from the dedicated USB power input (best when complete because you can provide enough current to drive a MIDI controller from the USB MIDI port), or the Teensy USB input (more convenient if regularly re-programming the Teensy)
Cut between the pads as shown to disconnect the USB voltage and the Teensy voltage input
Then solder wires to connect the USB host pads and the USB voltage
Place the Teensy and Teensy Audio Shield into their sockets to complete the lower board. The prototyping area provides a line of ground holes, a line of 3.3V holes, and multiple other 2.54mm holes, and could be particularly useful for providing additional controls connected to the extra pins on a Teensy 4.1

Building the Upper Board

Follow these steps to construct The EUCLIDEAN upper (controller) board.

At each stage carefully check continuity according to the schematic, orientation of components, and ensure there are no short circuits.

Components and panel for the upper board
Solder the PB86 switches — take care with the LED polarity (the ground pin is on the right hand side for all diodes except the two LED switches where the inner two pins are ground)
Add the other switches and the rotary controls
Place the upper panel (with some knobs to hold it) and check alignment
Solder the interconnect socket and the diodes, using the panel to ensure the diode height is correct
Solder the LCD pins, add spacers to adjust the height, check alignment and all diode heights. Check all rotary controls turn easily and widen holes if necessary
Optionally add a bypass capacitor to the MUX
Secure the top panel and upper board to the enclosure and add the knobs
Secure the rear panel and lower board to the enclosure
Add the connecting cable, then complete the enclosure

Congratulations! You're done.

The EUCLIDEAN Build Guide — © Ken Wessen 2020