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3. Calibrate

The driver learns your motor: you give it three values from the datasheet, and calibration measures the rest.

1. Restore the defaults

First the factory defaults, so that calibration does not start from another motor's values or from junk in the EEPROM.

Press Default in the settings.

#Default
What else #Default resets

It also resets the serial number, hardware version and batch date stored in the EEPROM; from firmware 109 it keeps the CAN node ID.

2. Enter the motor 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).
The three values on a typical datasheet, here for the 17HS16-2004S1: 1.8°, 1.1 Ω, 2.6 mH.
Figure 1: The three values on a typical datasheet, here for the 17HS16-2004S1: 1.8°, 1.1 Ω, 2.6 mH.

STEPFOC does not measure these; calibration fails on a value left at 0.

We recommend a Motor GUI preset

In Motor GUI's Presets tab, a preset enters these values for you, with safe limits and gains. For a Source Robotics product, pick its preset. For any other stepper, pick Generic motor and type the pole pairs, the resistance and the inductance from the datasheet: the preset writes them with a low current limit and soft loops, so the motor calibrates safely. More: Motor GUI.

Enter Pole pairs, Resistance and Inductance in the motor settings and apply them.

#PP 50
#R 1.1
#L 0.0026

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.

More: Motor parameters and calibration.

3. Calibrate

  1. Fix the motor to the bench, with nothing on the shaft.
  2. Set the supply to 24 V.

  3. Start the calibration:

    Start the calibration. The GUI switches to Calibration mode and shows the driver's log step by step.

    #Cal

  4. Keep the shaft free until the end, about a minute more after the log below.

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

Calibration success!
Next, by itself: the encoder table, then anti-cogging (about a minute; keep the shaft free). Everything is saved when they finish (#Encal state, #Cogcal state)
Going to idle!

The driver then goes on to measure the encoder table and the anti-cogging, and saves everything when they succeed.

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.

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.

More: Motor parameters and calibration, with the whole log and every message.

4. Set the current limit and save

The current limit is the motor's rated phase current in mA. It is 1700 mA after #Default, more than a small motor's rating.

Calibration uses its own 1600 mA for its steps and puts the limit back when it ends, and the encoder table after it runs at 80 % of the limit, so on a small motor set it before you calibrate (step 3); set it now in any case.

Set the current limit in the limits, then Save (the GUI warns about unsaved changes until you do).

#Ilim 1500
#Save

Without saving, the calibration is gone at the next power cycle. The LED now shows three short flashes and a pause: normal operation.

Three short flashes and a pause
Figure 2: Three short flashes and a pause.

Check

After Save, Motor GUI no longer marks unsaved changes, and after a power cycle #Info prints Calibrated. Saving explains which settings are kept.

More: Current limit and loop tuning · Saving the configuration.

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