The stepper motor that i have is a bipolar stepper motor.
On it one side there is information about it.
TYPE: 17PM-k310-33VS
NO. T4508-03
Minebea-Matsushita
Motor Corporation
Made in Thailand
It is a NEMA 17
17 stands for 1.7inches
| Raspberry Pi Pico W | L298N Module |
| GND | GND |
| GP0 | IN1 |
| GP1 | IN2 |
| GP2 | IN3 |
| GP3 | IN4 |
The two coils pair are found using the multimeter in resistance mode.
Since I am using a regular motor driver. I cannot do the micro stepping.
But even with micro stepping, it can do a lot of stuff.
So there are two coil pair.
step angle of 1.8o degrees.
So to make a 360o
we need 360o / 1.8o = 200 steps
So we can make a full rotation with 200 steps of 1.8 degrees each.
This is what is known as the full step.
In full step, we only excite 1 pole at a time. There are two poles per coil.
We can excite two poles at a time. Which will half the step angle to 0.9 degrees.
The following is the table I have made to see how many steps I will be made by employing a 0.9 deg angle. It is only up to 300 steps or 270 deg. You can calculate from then on.
Micropython Code
from machine import Pin
import utime
motor_pins = [Pin(0, Pin.OUT), Pin(1, Pin.OUT), Pin(2, Pin.OUT), Pin(3, Pin.OUT)]
step_sequence = [
[1,0,0,0],#1
[1,0,1,0],#13
[0,0,1,0],#3
[0,1,1,0],#23
[0,1,0,0],#2
[0,1,0,1],#24
[0,0,0,1],#4
[1,0,0,1]#41
]
off_seq = [(0,0,0,0)]
length_step_sequence = len(step_sequence)
one_rotation_length = 400/length_step_sequence
step_delay = (1/1000)*10 #ms
def step_off():
#print("step off")
motor_pins[0].value(0)
motor_pins[1].value(0)
motor_pins[2].value(0)
motor_pins[3].value(0)
utime.sleep(step_delay)
'''
Function Name: move_step
Description:
It takes the step sequence and assigns the motor pins to the value
according to the step sequence.
It moves one step seqence at a time.
For a half step sequence
each step will be 0.9 degrees.
For a full step sequence
each step will be 1.8 degrees.
'''
def move_step(seq):
ygh = seq
#print(ygh)
for step1,pins in zip(ygh,motor_pins):
pins.value(step1)
'''
Function Name: move one step
Description:
It moves all the steps in the sequence.
For a half wave steps => 8 * 0.9 = 7.2 deg
For a full wave steps => 4 * 1.8 = 7.2 deg
'''
def move_one_step(forward,reverse):
for i in range(0,length_step_sequence,1):
if forward == 1:
move_step((step_sequence[i]))
elif reverse == 1:
move_step(reversed(step_sequence[i]))
utime.sleep(step_delay)
def rotation(steps,forward,reverse):
if forward == 1:
for i in range(steps):
move_one_step(1,0)
print("Forward steps: ",steps)
elif reverse == 1:
for i in range(steps):
move_one_step(0,1)
print("Reverse steps: ",steps)
#step_off()
'''
Half step calculations
8 Steps of 0.9 deg each.
total degree of 8 steps => 8 * 0.9 = 7.2
(8 step sequence) * (50 repeated steps) * 0.9 deg = 360
So, a total of 400 steps are required to make 360 degree.
7.2 deg x (50 repeated steps) = 360 degrees
7.2 deg x 25 = 180 degree
'''
while True:
rotation(25,1,0) # move 180 forward(CW)
utime.sleep(1)
rotation(50,0,1) # move 366 reverse (CCW)
utime.sleep(1)
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