Hi,
I'm working on controlling a bipolar steppermotor with RPI using Python. The motor has 200 steps. I want to rotate the motor in intervals of anywhere between 12-18. I do believe if I use half stepping I can increase the amount of steps to 400 on the motor, which gives me multiples of 16.
I'm struggling with the sequence for halfstepping. The code I'm currently using:
Code import RPi.GPIO as GPIO
import time
# Variables
delay = 0.0055
steps = 50
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
# Enable pins for IN1-4 to control step sequence
coil_A_1_pin = 18
coil_A_2_pin = 23
coil_B_1_pin = 24
coil_B_2_pin = 25
# Set pin states
GPIO.setup(coil_A_1_pin, GPIO.OUT)
GPIO.setup(coil_A_2_pin, GPIO.OUT)
GPIO.setup(coil_B_1_pin, GPIO.OUT)
GPIO.setup(coil_B_2_pin, GPIO.OUT)
# Function for step sequence
def setStep(w1, w2, w3, w4):
GPIO.output(coil_A_1_pin, w1)
GPIO.output(coil_A_2_pin, w2)
GPIO.output(coil_B_1_pin, w3)
GPIO.output(coil_B_2_pin, w4)
# loop through step sequence based on number of steps
for i in range(0, steps):
setStep(1,0,1,0)
time.sleep(delay)
setStep(0,1,1,0)
time.sleep(delay)
setStep(0,1,0,1)
time.sleep(delay)
setStep(1,0,0,1)
time.sleep(delay)
The code rotates the motor one full revolution.
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So the motor has 200 steps, you send it only 50, but it moves a full rotation. What stepper motor and driver are you using exactly? If you want to post a pic of your wiring.
Well, the sequence steps the motor 4 times, and I loop through the sequence 50 times, adding up to a total of 200 steps. Using a 5V motor, bought it at a local store, it's from Luxorparts. And using a TB6612fng driver.
(Aug 2, 2017 05:22 AM)SIM-1517404 Wrote: Well, the sequence steps the motor 4 times, and I loop through the sequence 50 times, adding up to a total of 200 steps. Using a 5V motor, bought it at a local store, it's from Luxorparts. And using a TB6612fng driver.
🤝
post a pic or 2 of your setup
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Aug 2, 2017 06:42 AM
(This post was last modified: Aug 2, 2017 10:06 AM by Jomaki.)
Given in the for loop which actually controls the stepping there are four separate setStep commands, and you are doing four times less loops than there are steps, I am willing to bet that each of these setSteps does a singular step.
The code to explain what I am thinking:
Code import RPi.GPIO as GPIO
import time
# Variables
delay = 0.0055
steps = 200
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
# Enable pins for IN1-4 to control step sequence
coil_A_1_pin = 18
coil_A_2_pin = 23
coil_B_1_pin = 24
coil_B_2_pin = 25
# Set pin states
GPIO.setup(coil_A_1_pin, GPIO.OUT)
GPIO.setup(coil_A_2_pin, GPIO.OUT)
GPIO.setup(coil_B_1_pin, GPIO.OUT)
GPIO.setup(coil_B_2_pin, GPIO.OUT)
# Function for step sequence
def set_step(w1, w2, w3, w4):
GPIO.output(coil_A_1_pin, w1)
GPIO.output(coil_A_2_pin, w2)
GPIO.output(coil_B_1_pin, w3)
GPIO.output(coil_B_2_pin, w4)
# loop through step sequence based on number of steps
# gives us a list so we can essentially iterate through each of the different step values
# meaning we can iterate through each "part" of the original stepping sequence
step_values = [{"w1":1, "w2":0, "w3":1, "w4":0},
{"w1":0, "w2":1, "w3":1, "w4":0},
{"w1":0, "w2":1, "w3":0, "w4":1},
{"w1":1, "w2":0, "w3":0, "w4":1}]
current_step_count = 0
def step_motor():
needed_step_values = step_values[current_step_count % 4]
set_step(needed_step_values["w1"], needed_step_values["w2"], needed_step_values["w3"], needed_step_values["w4"])
time.sleep(delay)
current_step_count += 1
# this should turn everything off to stop them moving -- not sure if this is necessary
# trying commenting it out if it doesn't work with it in
set_step(0, 0, 0, 0)
for i in range(0, steps):
step_motor()
As I said in the comments, I am not certain if line 54 would be necessary. (note: I also changed setStep to set_step to be coherent with the rest of the code).
Try this out and let me know if it works.
EDIT: Just realised I added to the step count too early and fixed it.
(Aug 2, 2017 06:42 AM)Jomaki Wrote: Given in the for loop which actually controls the stepping there are four separate setStep commands, and you are doing four times less loops than there are steps, I am willing to bet that each of these setSteps does a singular step.
The code to explain what I am thinking:
Code import RPi.GPIO as GPIO
import time
# Variables
delay = 0.0055
steps = 200
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
# Enable pins for IN1-4 to control step sequence
coil_A_1_pin = 18
coil_A_2_pin = 23
coil_B_1_pin = 24
coil_B_2_pin = 25
# Set pin states
GPIO.setup(coil_A_1_pin, GPIO.OUT)
GPIO.setup(coil_A_2_pin, GPIO.OUT)
GPIO.setup(coil_B_1_pin, GPIO.OUT)
GPIO.setup(coil_B_2_pin, GPIO.OUT)
# Function for step sequence
def set_step(w1, w2, w3, w4):
GPIO.output(coil_A_1_pin, w1)
GPIO.output(coil_A_2_pin, w2)
GPIO.output(coil_B_1_pin, w3)
GPIO.output(coil_B_2_pin, w4)
# loop through step sequence based on number of steps
# gives us a list so we can essentially iterate through each of the different step values
# meaning we can iterate through each "part" of the original stepping sequence
step_values = [{"w1":1, "w2":0, "w3":1, "w4":0},
{"w1":0, "w2":1, "w3":1, "w4":0},
{"w1":0, "w2":1, "w3":0, "w4":1},
{"w1":1, "w2":0, "w3":0, "w4":1}]
current_step_count = 0
def step_motor():
needed_step_values = step_values[current_step_count % 4]
set_step(needed_step_values["w1"], needed_step_values["w2"], needed_step_values["w3"], needed_step_values["w4"])
time.sleep(delay)
current_step_count += 1
# this should turn everything off to stop them moving -- not sure if this is necessary
# trying commenting it out if it doesn't work with it in
set_step(0, 0, 0, 0)
for i in range(0, steps):
step_motor()
As I said in the comments, I am not certain if line 54 would be necessary. (note: I also changed setStep to set_step to be coherent with the rest of the code).
Try this out and let me know if it works.
EDIT: Just realised I added to the step count too early and fixed it.
Sorry for the late response, I've been away for a couple of weeks.
The result I get from running the code is:
Code Traceback (most recent call last):
File "StepperTest.py", line 68, in <module>
step_motor()
File "StepperTest.py", line 58, in step_motor
needed_step_values = step_values[current_step_count % 4]
UnboundLocalError: local variable 'current_step_count' referenced before assignment
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(Aug 15, 2017 12:01 PM)SIM-1517404 Wrote: Sorry for the late response, I've been away for a couple of weeks.
The result I get from running the code is:
Code Traceback (most recent call last):
File "StepperTest.py", line 68, in <module>
step_motor()
File "StepperTest.py", line 58, in step_motor
needed_step_values = step_values[current_step_count % 4]
UnboundLocalError: local variable 'current_step_count' referenced before assignment
PHP Code
<?php
current_step_count = 0
def step_motor():
global current_step_count #ADD ME
needed_step_values = step_values[current_step_count % 4]
set_step(needed_step_values["w1"], needed_step_values["w2"], needed_step_values["w3"], needed_step_values["w4"])
time.sleep(delay)
current_step_count += 1
See #add me. If you do this (current_step_count += 1) you need to add the global statement.
(Aug 16, 2017 12:30 PM)datguy.dev Wrote: PHP Code
<?php
current_step_count = 0
def step_motor():
global current_step_count #ADD ME
needed_step_values = step_values[current_step_count % 4]
set_step(needed_step_values["w1"], needed_step_values["w2"], needed_step_values["w3"], needed_step_values["w4"])
time.sleep(delay)
current_step_count += 1
See #add me. If you do this (current_step_count += 1) you need to add the global statement.
It does one full rotation now. How can I change the sequence to allow half-stepping? I would like 400 steps per revolution so that I can have intervalls of 16. 25 steps, delay for 5 seconds and repeat 16 times.
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