AN3208

Driving stepper motors using STM8A and STM8S microcontrollers

Doc ID 17411 Rev 1

11/19

The current in the motor windings is controlled by varying the PWM duty cycle values. The

PWM duty cycle for each microstep depends on the phase angle of currents in the two

windings. The duty cycles of Table 1 are calculated using the current waveforms of

Figure 10. The same table can be generated for other motors using the same method. For

more details about duty cycle calculation see Section 5.2: Software description.

Note:

Table 1 shows theoretical duty cycle values. Contact the stepper motor supplier for

exact/customized values.

Table 1.

PWM duty cycles for an M-S motor

Step no.

Step

angle

(°)

Phase

angle (°)

coil 1

Phase

angle (°)

coil 2

Sine value

(°)

coil 1

Sine value

(°)

coil 2

PWM duty

cycle (%)

coil 1

PWM duty

cycle (%)

coil 2

1

0

60

120

0.87

0.87

87

87

2

15

75

135

0.97

0.71

97

71

3

30

90

150

1.00

0.50

100

50

4

45

105

165

0.97

0.26

97

26

5

60

120

180

0.87

0.00

87

0

6

75

135

195

0.71

-0.26

71

26

7

90

150

210

0.50

-0.50

50

50

8

105

165

225

0.26

-0.71

26

71

9

120

180

240

0.00

-0.87

0

87

10

135

195

255

-0.26

-0.97

26

97

11

150

210

270

-0.50

-1.00

50

100

12

165

225

285

-0.71

-0.97

71

97

13

180

240

300

-0.87

-0.87

87

87

14

195

255

315

-0.97

-0.71

97

71

15

210

270

330

-1.00

-0.50

100

50

16

225

285

345

-0.97

-0.26

97

26

17

240

300

360

-0.87

0.00

87

0

18

255

315

15

-0.71

0.26

71

26

19

270

330

30

-0.50

0.50

50

50

20

285

345

45

-0.26

0.71

26

71

21

300

360

60

0.00

0.87

0

87

22

315

15

75

0.26

0.97

26

97

23

330

30

90

0.50

1.00

50

100

24

345

45

105

0.71

0.97

71

97

25

360

60

120

0.87

0.87

87

87