Driving a bi-polar stepper motor with the

SN754410NE double H-bridge

Bi-polar stepping motors use only two coils and are easily recognized because they only have four wires. Most unipolar steppers can be used in bipolar mode by ignoring the two centre taps. Because bi-polar stepping motors produce the rotating magnetic field by reversing the current in both coils, controlling them is much more complicated than controlling their unipolar cousins.

My circuit makes use of a SN754419 dual h-bridge chip, which takes all the hard work out of designing an interfacing circuit. As can be seen in the circuit diagram below, my circuit merely connects the chip to the relevant terminals. In fact, the board is so bare that I added a power on LED out of pure embarrassment. I run my motor at 5V. If you use a motor with a higher voltage, you have to split the supply via the link and provide a 5V logic supply via a tap from the Velleman board. The motor supply will then be connected to pin 9 and the logic positive to pin 8.

Below is a suggested PCB layout at 2*magnification. Notice that the four centre earth pins also serve as a heat sink. This of course explains the large copper area.

My program drives the motor in both directions at nine different speeds. It allows both half step and full step mode.

Below is a link to a zip archive with the BBC Basic file and also a self-executing file which allows you to try the program whether you have BBC BASIC for Windows or not.

K8055_bi-polar_stepper_1_0.zip

Here are the same two files for the K8061

K8061_bi-polar_stepper_1_0.zip

10 REM Bi-polar stepper driver 20 REM For The Velleman K8055N USB interface 30 REM Jochen Lueg 40 REM http://roevalley.com/newsbrowser/v-projects/v-index.htm 50 REM Limavady, May 2012 60 REM Version 1.0 70 80 ON ERROR PRINT ERL;" ";REPORT$:END 90 PROCK8055_init 100 PROCinit 110 PROCwindow(600,400,"Bi-polar stepper driver") 120 OFF 130 ON ERROR PROCerror 140 SYS K8055_CloseDevice% 150 SYS K8055_OpenDevice%,0 160 SYS K8055_WriteAllDigital%,%11110000 170 ON CLOSE PROCclose 180 PRINT 190 PRINT " Motor controls" 200 PRINT 210 PRINT " Left . . . . . . Z" 220 PRINT " Right . . . . . . C" 230 PRINT " Stop . . . . . . X" 240 PRINT " Full step . . . . . . F" 250 PRINT " Half step . . . . . . H" 260 PRINT 270 PRINT " Fastest . . . . . . 1" 280 PRINT " to" 290 PRINT " Slowest . . . . . . 9" 300 PRINT 310 PRINT " Press 'Q' to leave the program" 320 330 REPEAT 340 Key$=INKEY$(0) : REPEAT UNTIL INKEY(0)=-1 350 IF Key$="c" OR Key$="C" Direction$="Right" 360 IF Key$="z" OR Key$="Z" Direction$="Left" 370 IF Key$="q" OR Key$="Q" Direction$="Finished" 380 IF Key$="x" OR Key$="X" Direction$="Stop" 390 IF Key$="h" OR Key$="H" Mode$="Half" 400 IF Key$="f" OR Key$="F" Mode$="Full" 410 IF Key$="1" T%=150*S% :Speed$="Fast" 420 IF Key$="2" T%=200*S% :Speed$="Fast-1" 430 IF Key$="3" T%=300*S% :Speed$="Fast-2" 440 IF Key$="4" T%=625*S% :Speed$="Fast-3" 450 IF Key$="5" T%=1250*S% :Speed$="Half" 460 IF Key$="6" T%=2500*S% :Speed$="Slow+3" 470 IF Key$="7" T%=5000*S% :Speed$="Slow+2" 480 IF Key$="8" T%=10000*S% :Speed$="Slow+1" 490 IF Key$="9" T%=20000*S% :Speed$="Slow" 500 IF Direction$="Right" AND Mode$="Full" THEN PROCfull_step_right 510 IF Direction$="Right" AND Mode$="Half" THEN PROChalf_step_right 520 IF Direction$="Left" AND Mode$="Full" THEN PROCfull_step_left 530 IF Direction$="Left" AND Mode$="Half" THEN PROChalf_step_left 540 IF Direction$="Stop" PRINTTAB(1,18)"Motor stopped " 550 IF Direction$="Stop" SYS K8055_ClearAllDigital%:Direction$="Wait" 560 IF Direction$ <> "Wait" PRINTTAB(1,18);Mode$;" step. Turning ";Direction$;" with speed ";Speed$;" " 570 UNTIL Direction$="Finished" 580 PROCclose 590 END 600 610 620 630 DEFPROCfull_step_right 640 FOR J%=1 TO 4 650 SYS K8055_WriteAllDigital%,FullStep%(J%): FOR I%=1 TO T%:NEXT 660 NEXT 670 ENDPROC 680 690 700 DEFPROCfull_step_left 710 FOR J%=4 TO 1 STEP -1 720 SYS K8055_WriteAllDigital%,FullStep%(J%): FOR I%=1 TO T%:NEXT 730 NEXT 740 ENDPROC 750 760 770 DEFPROChalf_step_right 780 FOR J%=1 TO 8 790 SYS K8055_WriteAllDigital%,HalfStep%(J%): FOR I%=1 TO T%:NEXT 800 NEXT 810 ENDPROC 820 830 840 DEFPROChalf_step_left 850 FOR J%=8 TO 1 STEP -1 860 SYS K8055_WriteAllDigital%,HalfStep%(J%): FOR I%=1 TO T%:NEXT 870 NEXT 880 ENDPROC 890 900 910 DEFPROCinit 920 W%=0 930 Direction$="Stop" 940 S%=800 950 T%=S%*35 960 Speed$="Fast" 970 Mode$="Full" 980 990 1000 DIM FullStep%(4) 1010 FullStep%(1)=%1000 <<4 1020 FullStep%(2)=%0010 <<4 1030 FullStep%(3)=%0100 <<4 1040 FullStep%(4)=%0001 <<4 1050 1060 DIM HalfStep%(8) 1070 HalfStep%(8)= %1010 <<4 1080 HalfStep%(7)= %1000 <<4 1090 HalfStep%(6)= %1001 <<4 1100 HalfStep%(5)= %0001 <<4 1110 HalfStep%(4)= %0101 <<4 1120 HalfStep%(3)= %0100 <<4 1130 HalfStep%(2)= %0110 <<4 1140 HalfStep%(1)= %0010 <<4 1150 1160 ENDPROC 1170 1180 1190 DEFPROCerror 1200 PRINT REPORT$;" at line ";ERL : 1210 SYS K8055_ClearAllDigital% 1220 SYS K8055_CloseDevice% 1230 SYS "FreeLibrary",K8055_Board% 1240 END 1250 ENDPROC 1260 1270 1280 DEFPROCclose 1290 SYS K8055_ClearAllDigital% 1300 SYS K8055_CloseDevice% 1310 SYS "FreeLibrary",K8055_Board% 1320 QUIT 1330 ENDPROC 1340 1350 1360 DEFPROCwindow(WindowWidth%,WindowHeight%,Wt$) 1370 MODE 30 1380 SYS "SetWindowPos",@hwnd%,0,0,0,WindowWidth%,WindowHeight%,6 1390 COLOUR 128 1400 CLS 1410 COLOUR 15 1420 VDU 26 1430 SYS "SetWindowText",@hwnd%,Wt$ 1440 *FONT Lucida Console,14,2 1450 ENDPROC 1460 1470 1480 1490 DEFPROCK8055_init 1500 REM Typing errors in routine name do not generate an error message - they just hang up the program. 1510 REM These are all the system calls in the order found in the manual 1520 SYS"LoadLibrary","K8055D.dll" TO K8055_Board% 1530 SYS"GetProcAddress",K8055_Board%,"OpenDevice" TO K8055_OpenDevice% 1540 SYS"GetProcAddress",K8055_Board%,"CloseDevice" TO K8055_CloseDevice% 1550 SYS"GetProcAddress",K8055_Board%,"ReadAnalogChannel" TO K8055_ReadAnalogChannel% 1560 SYS"GetProcAddress",K8055_Board%,"ReadAllAnalog" TO K8055_ReadAllAnalog% 1570 SYS"GetProcAddress",K8055_Board%,"OutputAnalogChannel" TO K8055_OutputAnalogChannel% 1580 SYS"GetProcAddress",K8055_Board%,"OutputAllAnalog" TO K8055_OutputAllAnalog% 1590 SYS"GetProcAddress",K8055_Board%,"ClearAnalogChannel" TO K8055_ClearAnalogChannel% 1600 SYS"GetProcAddress",K8055_Board%,"ClearAllAnalog" TO K8055_ClearAllAnalog% 1610 SYS"GetProcAddress",K8055_Board%,"SetAnalogChannel" TO K8055_SetAnalogChannel% 1620 SYS"GetProcAddress",K8055_Board%,"SetAllAnalog" TO K8055_SetAllAnalog% 1630 SYS"GetProcAddress",K8055_Board%,"WriteAllDigital" TO K8055_WriteAllDigital% 1640 SYS"GetProcAddress",K8055_Board%,"ClearDigitalChannel" TO K8055_ClearDigitalChannel% 1650 SYS"GetProcAddress",K8055_Board%,"ClearAllDigital" TO K8055_ClearAllDigital% 1660 SYS"GetProcAddress",K8055_Board%,"SetDigitalChannel" TO K8055_SetDigitalChannel% 1670 SYS"GetProcAddress",K8055_Board%,"SetAllDigital" TO K8055_SetAllDigital% 1680 SYS"GetProcAddress",K8055_Board%,"ReadDigitalChannel" TO K8055_ReadDigitalChannel% 1690 SYS"GetProcAddress",K8055_Board%,"ReadAllDigital" TO K8055_ReadAllDigital% 1700 SYS"GetProcAddress",K8055_Board%,"ResetCounter" TO K8055_ResetCounter% 1710 SYS"GetProcAddress",K8055_Board%,"ReadCounter" TO K8055_ReadCounter% 1720 SYS"GetProcAddress",K8055_Board%,"SedtCounterDebouceTime" TO K8055_SetCounterDebounceTime% 1730 ENDPROC

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