Step motor control

[aratti]

You can improve your motor performance in two ways:

1) Use half step sequence ( here a sample code)

HStep           var byte    [8]     ' Half step sequence array
B0              var byte
C0              var byte
P0              var byte
W0              var word

TRISB = 0


P0 = 50   ' incrementing the delay will reduce the motor speed  (max 255)
C0 = 0
B0 = 0

HalfMode:                      
If C0 = 0 then gosub CW
C0 = C0 + 1
if C0 = 2 then C0 = 0
If C0 = 0 then gosub CW
If C0 = 1 then gosub CCW

for W0 = 0 to 8192   ' one turn of the gear shaft ( 64 motor turns)
PortB = HStep[B0]
B0 = B0+1   
if B0 = 8 then B0=0
pause P0
next W0

Goto HalfMode

CW:        ' half step sequence (clockwise)
HStep[0] = 1
HStep[1] = 3
HStep[2] = 2
HStep[3] = 6
HStep[4] = 4
HStep[5] = 12
HStep[6] = 8
HStep[7] = 9
return

CCW:       ' half step sequence (counter clockwise)
HStep[0] = 9
HStep[1] = 8
HStep[2] = 12
HStep[3] = 4
HStep[4] = 6
HStep[5] = 2
HStep[6] = 3
HStep[7] = 1
return

end

2) Use a constant current setup to your motor. The simple way is to use a LM317 configured as costant current supply. See the attached schematic (Resistor 33 Ohms 1 watt. Use 24 V dc as an input to the LM317)

cheers

Al.

[dragan77]

Thks,all for help!!!
I tired testing all code,I hope I do something!
Just one question,
Is possible make some code in picbasic,

When I start step motor,to start every time to one position,
example:

If step motor work some,go to left,go to right,.......
and I stop power,and turn again,is possible,motor back in some start position,and continue work some function!

[aratti]

Check this thread http://www.picbasic.co.uk/forum/showthread.php?t=12248 perhaps you will Find what you need!

Cheers

Al.

[dragan77]

This code work very nice!
Is very precision!
I testing yes-today!

Delay VAR BYTE
i VAR WORD

TRISB = 0  ' All outputs.

Delay = 10   ' ~100steps / second

For i = 1 to 1000    '1000 steps forward.
  PORTB = %00000001
  Pause Delay
  PORTB = %00000010
  Pause Delay
  PORTB = %00000100
  Pause Delay
  PORTB = %00001000
  Pause Delay
NEXT

Pause 2500

For i = 1 to 1000    '1000 steps reverse.
  PORTB = %00001000
  Pause Delay
  PORTB = %00000100
  Pause Delay
  PORTB = %00000010
  Pause Delay
  PORTB = %00000001
  Pause Delay
NEXT

But I don't now what is happens,
work well 5-6 min,and in the moment stop,like some reset happened,I don't now ,
and start over again,I don't why!

[HenrikOlsson]

Hi,
If it looks like a reset it probably is. There's no bypass capacitor in the schematic, if you don't have that in your circuit make sure you add one. 0.1uf right across the Vdd/Vss pins.

[dragan77]

Thks man!
I make this, you mean across + an -,from power!
I see that many time in shema,why is that nessery?

Now I testing this code:

Delay VAR BYTE
i VAR WORD

TRISB = 0           ' All outputs.

Delay = 8           
pause 1000
For i = 1 to 512    '512 steps forward.
  PORTB =9
  Pause Delay
  PORTB =3
  Pause Delay
  PORTB =6
  Pause Delay
  PORTB =12
  Pause Delay
  
NEXT
pause 2500


For i = 1 to 256    '256 steps reverse.
  PORTB =12
  Pause Delay
  PORTB =6
  Pause Delay
  PORTB =3
  Pause Delay
  PORTB =9
  Pause Delay
NEXT
Pause 2500

For i = 1 to 256    '256 steps reverse.
  PORTB =12
  Pause Delay
  PORTB =6
  Pause Delay
  PORTB =3
  Pause Delay
  PORTB =9
  Pause Delay
NEXT
Pause 1500

For now, working 2 hour fine,is precison,and dont have some reset,we will se for now!

And one more question,is possible make some code for picbasic for this:

If step motor work some,go to left,go to right,.......
and I stop power,and turn again,is possible,motor back in some start position,(some zero posicion),and continue work same function,before stoping!

[HenrikOlsson]

Yes, between pin 14 and 5 on the PIC as close to the chip as possible.
It's needed because as the current thru the circuit fluctuates (rises and falls) quickly (which it does in digital circuits, not to mention motor control and other "high power" circuits) the resistance and inductance of the wires and/or PCB traces that "feeds" the chip makes the voltage at the chip unstable.

If you look at ANY profesional PCB/circuit you'll see a bypass capacitor right next to EVERY chip for this particular reason.

[dragan77]

I wrong for last questin,I mean:
And one more question,is possible make some code for picbasic for this:

If step motor work some,go to left,go to right,.......
and I stop power,and turn again,is possible,motor back in some start position,(some zero posicion),and continue work same function,FROM START CODE!