MIDI and CV/Gate to Stepper Motor 12HP Eurorack

Introduction Video

https://youtu.be/hMhLqPYqAdg

Description

MotorPot is an automated high torque step motor that can work in a standalone mode or being controlled externally. It has an OLED screen to show current operation state which is selected and configured via simple MIDI commands such as Note On/Off and CC values.

MotorPot can be controlled by MIDI via USB MIDI Class Compliant, MIDI input (TRS-A or TRS-B selectable) and via CV/Gate for certain parameters. The incoming data over TRS MIDI is transferred to USB out too. This allows to record all incoming messages into DAW from external MIDI controllers without reconfiguration.

Step motors are very precise in the positioning, however, keep in mind there is no position feedback from them, i.e. they don’t know the actual position and can only rely on counting steps during operation. This results in two limitations. You need to set the 0-point at power on if position is not a zero. If the load on the motor is heavy and exceeds stepper power (say you control a tough rotary switch) it may skip a step. On a positive note it brings many advantages, as step motors are more powerful than servos or automated potentiometers. You’re also able to control multi-turn pots or other custom actuators with very high precision. It’s very flexible.

Unlike other Eurorack modules, MotorPot may require external power to operate. Very often 12V rail is limited in Eurorack PSUs. Given that stepper motor consumption can approach 2A at peak loads, it’s recommended to use a dedicated 12V PSU connected to the back of the unit (2.1x5.5, center positive). Other logic such as a microcontroller kept powered from Eurorack or USB input depends on the controller pin configuration (refer to the assembly guide).

MotorPot has several operational modes which are saved in its non-volatile memory together with other parameters. You can set and remember positions and recall them with MIDI notes, track a modulation wheel with CC1, rotate it at the constant speed or bounce between two positions (refer to the manual for the setup and usage).
MotorPot firmware is open source under BSD 3-Clause License making the contributions easy and welcomed for the community. Additional functionality can be added and merged into the existing repository.

Purchasing options:

• DIY Kit: Comes with everything that's needed to build the board except Teensy 4.0 and the external 12V power brick.
• Assembled board: this option has limited availability depends on the production load.
• Optional Programmed Teensy 4.0: you can by Teensy directly from PJRC or get it from us with the latest loaded firmware.

Assembly instructions:

Refer to Github for Schematics, BOM and detailed assembly instruction: GitHub Link

Github file repository:

https://github.com/Deftaudio/Midi-boards/tree/master/Eurorack_MotorPot

Andrei Kudryavtsev, Deftaudio 2008-2023.