Stepper motor characterization

AN3991

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DocID022332 Rev 2

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Stepper motor characterization

Determine Rph, the resistance per phase, and Lph, the inductance per phase for the

stepper motor. These are available from the stepper motor datasheet. These parameters

are needed to optimize the back EMF compensation. Also Ke, the motor back EMF constant

is needed. This is easily measured as described in the evaluation software help file (see

also dSPIN Ke measurement in Section : Motor back EMF constant (Ke) measurement on

page 11 of this document).

1.8 degree stepper motors are used in this evaluation.

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Running the motor evaluation

After connecting the power supply and the stepper motors, and setting JP2 on each

EVAL6470H, turn on the power supply. Run the dSPIN evaluation tool.

You can find the application shortcut in the Windows start menu:

Start|Programs|STMicroelectronics|dSPIN evaluation Tool|dSPIN evaluation tool. Select the

STEVAL-PCC009V2 interface board.

Connect the USB connector from the STEVAL-PCC009V2 to the PC’s USB port. Complete

the driver installation as described in the dSPIN evaluation tool help file.

Click the “Connect Board” button in the toolbar (or select the menu item ToolsIConnect

board). The board connection status is indicated in the lower left corner.

The positioning tab is highlighted.

The device 1 is highlighted at the top of the display. The device 1 is the motor 1, the first of

three motors.

Physically move the shaft of the motor 1 to a position defined as “home” for demonstration

purposes.

Next, implement the back EMF compensation. Click the BEMF icon (or Tools|BEMF

compensation). Fill in the application parameters and motor parameters (Rph, Lph, Ke).

Click “Evaluate”, and then “Write”.