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What you need

This page lists what a STEPFOC setup is made of, what comes with the driver, and what you buy or make yourself.

The driver

STEPFOC is sold as a single driver or as a starter kit in the Source Robotics shop:

Every driver is end-of-line tested and ships with the current firmware release and the bootloader already installed, so a driver works out of the box with a serial terminal, the Python library or Motor GUI. The firmware can be updated later without a programming adapter; see Firmware.

A stepper motor

STEPFOC drives bipolar (4-wire) stepper motors. It is made for the NEMA 17 frame, whose mounting holes match the board; it also works with NEMA 23 motors on the NEMA 23 spacer, and with other frames on an adapter you make. Look for a motor with a phase resistance of 1 to 5 Ω and a rated current of 3 A or less; the tested motors are known to work.

The encoder magnet

A diametrically magnetised 6 × 2.5 mm neodymium magnet on the rear of the motor shaft, about 1 mm above the encoder chip in the middle of the board: 6 × 2.5 mm diametrical magnet. An axially magnetised magnet, or one that wobbles, makes calibration fail or report bad positions. The 6 × 2.5 mm size is the stock one, not a requirement: another thickness is a way to set the 1 mm gap when a shaft or a spacer leaves the wrong distance. The encoder magnet says how to fit it.

Adapters and cables

Part Needed for Shop
USB-to-serial adapter (3.3 V) the serial terminal: calibration, tuning, any # command Serial adapter
CANvas USB-to-CAN adapter CAN control from a PC, the Python library, Motor GUI over CAN CAN adapter
CAN cable and power cable daisy-chaining several drivers CAN cable, power cable
100 kΩ NTC thermistor motor temperature protection (optional but recommended) Thermistor
JTAG programming adapter only for installing the bootloader on an older board, or for firmware development Programming adapter

Cable orientation

The daisy-chain cables for CAN and power are keyed by their orientation, not by their connector. A cable plugged in the wrong way round destroys the driver. Use the cables from the shop or follow Power and the CAN daisy chain exactly when you make your own.

A power supply

12 to 29 V DC, 24 V recommended; see Ratings and limits. Calibrate at 24 V: the motor constants come out wrong at a lower voltage. A bench supply with a current limit is the safest way to start.

Software

  • Motor GUI, in the browser, over the serial adapter or the CAN adapter: the usual tool for setup, calibration, tuning, plots and firmware updates; see Motor GUI.
  • Or a serial terminal: PuTTY, the PlatformIO monitor in VS Code, or the Arduino serial monitor; see The serial terminal.
  • The Python library Spectral-BLDC for CAN control from your own programs; see With Python.

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