Quick start¶
From the box to a calibrated motor that follows commands, on one page. The quickest way through is Motor GUI in the browser; every step also shows the terminal commands, and ends with a link to the chapter that explains it. Follow the link when a step is not clear or something fails.
Read first
Reversed supply polarity, a daisy-chain cable the wrong way round, or 5 V on the UART port destroys the driver. The motor turns during calibration. The Safety chapter is two minutes long.
1. What you need¶
| Where to get it | |
|---|---|
| STEPFOC driver | single driver or the starter kit, which has everything below except the motor and the supply |
| A bipolar stepper motor with a rear shaft: NEMA 17, 1 to 5 Ω per coil, 3 A or less | the tested motors are safe choices |
| The encoder magnet, diametrically magnetised; the stock one is 6 × 2.5 mm, another thickness is fine if it gives the 1 mm gap | magnet |
| A spacer for your motor length and four longer M3 screws | printable spacers in Stepper motor accessories |
| USB-to-serial adapter, 3.3 V, and its cable | serial adapter, UART cable |
| Power cable | power cable |
| A 12 to 29 V supply, 24 V recommended | a bench supply with a current limit is the safest start |
| For CAN later: CANvas USB-to-CAN adapter and a CAN cable | CAN adapter, CAN cable |
| Optional: 100 kΩ NTC thermistor for motor temperature protection | thermistor |
| Software: Motor GUI in Chrome or Edge, or a serial terminal | motorgui.com; PuTTY, the PlatformIO monitor or the Arduino serial monitor |
Read in more detail: What you need.
2. Fit the magnet¶
Press the magnet onto the rear shaft, centred, and glue it. It must end up about 1 mm above the encoder chip in the middle of the board, and it must not be able to turn on the shaft. A magnet that slips is the usual cause of a calibration that "succeeds" and a motor that then runs badly.
Read in more detail: The encoder magnet.
Check
The magnet sits centred on the shaft, and once the glue has set it does not move when you push it with a finger. If it does: The encoder magnet.
3. Mount the board¶
Remove the motor's four rear screws, put the spacer on, the board on the spacer with the encoder chip towards the magnet, and the longer screws in. Check the gap: 1 mm, not touching.
Read in more detail: Mounting on the motor.
Check
The board sits parallel to the back of the motor, about 1 mm above the magnet, and the shaft turns by hand without the magnet touching the chip. If not: Mounting on the motor.
4. Wire the motor¶
Find the two coils with a multimeter (the two wires of a coil show a few ohms; wires of different coils show nothing). Solder one coil to A+ and A−, the other to B+ and B−. Which coil is which, and which way round, does not matter: calibration detects it.
Read in more detail: Wiring the stepper.
Check
With the driver unpowered, a multimeter shows the coil's resistance, a few ohms, between A+ and A− and between B+ and B−, and no strand bridges two pads. If not: Wiring the stepper.
5. Connect power and the PC¶
- The supply to a power connector: DC+ to positive, DC− to negative. Check twice.
- The serial adapter to the UART connector with the UART cable (TX to RX, RX to TX; 3.3 V only).
- Power on. The LED blinks for about two seconds while the bootloader waits for a host, then the firmware starts and the LED stays on steadily: the driver is not calibrated yet, which it reports as an error state. (The serial adapter alone powers the driver's logic: it answers over UART without the supply, but reports a Vbus error and will not calibrate or move.)
Open motorgui.com in Chrome or Edge, choose the serial connection and Connect on the adapter's port. The driver's identity and state appear: hardware and firmware version, serial number, Not calibrated, No errors. If nothing connects: the port, the cable's TX/RX, the browser (Web Serial needs a Chromium browser).
Read in more detail: Motor GUI.
Open a terminal on the adapter's port, 256000 baud, line ending CR+LF, and type #Info. The driver prints its
hardware and firmware version, its calibration state and the motor parameters; #Error prints the active
errors.
Read in more detail: The serial terminal.
Read in more detail: Power and the CAN daisy chain · Connectors and pinout.
Check
The driver's identity and live state appear before you change settings. A missing connection is covered in Motor GUI or Troubleshooting.
6. Restore the defaults and enter the motor parameters¶
First the factory defaults, so that calibration does not start from another motor's values or from junk in the
EEPROM: Default in the Motor GUI settings, or #Default in the terminal. (It also sets the CAN node ID to 0,
and resets the serial number, hardware version and batch date stored in the EEPROM.) Then the parameters:
From the motor's datasheet, for one coil: the pole pairs (50 for a 1.8° motor, 100 for 0.9°), the phase resistance in ohms, the phase inductance in henries (2.6 mH = 0.0026). STEPFOC does not measure these; calibration fails on a value left at 0.
Read in more detail: Motor parameters and calibration.
Check
#Info prints the values you entered as Number of pole pairs, Single phase resistance and Single
phase Inductance (Motor GUI shows them in the motor settings). None of them may be 0.
7. Calibrate¶
Fix the motor to the bench, nothing on the shaft, 24 V on the supply.
The LED flashes, the motor turns in both directions, and the driver reports each step: the pole pairs, the magnet, the supply, the parameters you entered, the open-loop spin, the angle offset, the motor constants, and finally
A failed step names itself, and the log ends with Calibration failed!. Magnet test: Failed is the magnet;
Phase order is wrong! means the motor did not turn or did not respond: check the four wires, the supply, and
that the magnet does not slip.
Read in more detail: Motor parameters and calibration, with the whole log and every message.
Check
The calibration log ends with Calibration success!. If it does not, use the failed step in
Calibration troubleshooting; do not treat a stopped motor as
success.
8. Set the current limit and save¶
The current limit is the motor's rated phase current in mA. It is 1700 mA after #Default, and calibration leaves
it at 1600 mA: both are more than a small motor's rating, so set it now, after calibrating.
Without saving, the calibration is gone at the next power cycle. The LED now shows three short flashes and a pause: normal operation.
Read in more detail: Current limit and loop tuning · Saving the configuration.
Check
After Save, Motor GUI no longer marks unsaved changes, and after a power cycle #Info prints
Calibrated. Saving explains which settings are kept.
9. Move it¶
Use the jog controls: Jog velocity turns the motor at a speed, Jog position moves it to a position, Jog current applies a torque; Send setpoint sends a value in the current control mode. The plots show position, speed and current while it moves.
Position is in encoder ticks, 16384 per revolution; speed in ticks per second; current in mA. If the motor hums or whines, lower the current limit or tune the loops.
Read in more detail: Control modes · Current limit and loop tuning.
Check
The position and speed feedback follow the request, and Idle stops driving the motor. A motor that does not follow needs Troubleshooting before a load is attached.
10. Where to go next¶
| You want to | Read |
|---|---|
| get to know Motor GUI: the screen, the plots, recordings, several motors | Motor GUI, Working in Motor GUI |
| control the driver from a program over CAN | Over CAN, then With Python |
| put several drivers on one bus | give each a node ID and terminate the ends: Power and the CAN daisy chain |
| protect the motor from overheating | Thermistor |
| update the firmware | Firmware |
| look up a message or a command | API reference |
| understand why it does not work | Errors and recovery, Troubleshooting |
Comments
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