Juju

9 minutes ago, vlaiv said:

That code style is not the best for what you are trying to achieve.

Don't use pauses that you don't precisely control - use active loop for good precision (this will drain more power but you want as "real time" as possible).

Here is pseudo code for something like this:

while not done:
  if current_time>=time_of_next_event:
    perform_next_event // like make step forward or step backward
    time_of_next_event = calculate_time_of_next_event(current_time, time_of_next_event)
  else:
    // here you can do microsleep if you want to save power or just do nothing and resume next step in iteration

As for timing - it is simple.

Sidereal rate is 15.043"/s

You need to calculate how many micro steps you have per revolution.

For example - let's say that your worm gear is 180:1 and that you are using standard stepper with 1.8 degrees step (200 steps per revolution) and you have 32 micro steps.

One full revolution will have in that case 180 * 200 * 32 = 1152000 steps

One full revolution, on the other hand has 360 * 60 * 60 = 1296000 arc seconds.

If you divide these two numbers - you will get arc seconds per step 1296000/1152000 = 1.125 arc seconds per step

Now we have 15.043"/s and 1.125"/step we can then divide those two to give us timing information

15.043 / 1.125 = 13.371555.... steps per second or

1.125 / 15.043 = ~0.0747856s per step or 74.7856 milliseconds per step or 74785.6 microseconds per step

In above pseudo code you would then put

time_of_next_event = time_of_this_event + 0.0747856s

I am a complete beginner in python, to further learn on the style of coding you mentioned i would just need to research active loops? and thank you for explaining the calculation

Thank you all for replying to my question I appreciate the time taken to reply.

As this is my first post I'm not sure how exactly to word this.

I started a project where i am trying to create a DIY RA Drive instead of buying a commercial one, I have successfully created a bracket and my wiring is all completed and works fine, however this may seem ridicule but I don't know how to match the rotation of the stepper to the earths rotation, in other words I am not sure on how to calculate the delay in which I need to send a signal for pulses.

Below is the code i am using.

i have up to 32 micro steps and am using python on a raspberry pi 3+.

I have seen many people complete this project but all guides have been using Arduinos.

Below is my code, could someone be so kind as to explain how i would go about the above problem? many thanks

As said above the code and hardware works fine it is just the steps and how to match earths rotation i do not understand.

from time import sleep
import RPi.GPIO as GPIO
from tkinter import *
from tkinter import messagebox
#
PUL = 17  # Stepper Drive Pulses
DIR = 27  # Controller Direction Bit (High for Controller default / LOW to Force a Direction Change).
ENA = 22  # Controller Enable Bit (High to Enable / LOW to Disable).
channel = 2 #Relay GPIO is set as channel
GPIO.setmode(GPIO.BCM)
#
GPIO.setup(PUL, GPIO.OUT)
GPIO.setup(DIR, GPIO.OUT)
GPIO.setup(ENA, GPIO.OUT)
GPIO.setup(channel, GPIO.OUT) #Relay GPIO Set up

durationFwd = 1000
delay = 0.05 # This is actualy a delay between PUL pulses - effectively sets the mtor rotation speed.
print('Speed set to ' + str(delay))

def Relay_on():
    GPIO.output(2, GPIO.LOW)  # Turn motor on

def Relay_off():
    GPIO.output(2, GPIO.HIGH)  # Turn motor off

def Exit():
    GPIO.cleanup()
    exit()
   
def forward():
    GPIO.output(ENA, GPIO.HIGH)
   
    print('ENA set to HIGH - Controller Enabled')
    #
    sleep(.1) # pause due to a possible change direction
    GPIO.output(DIR, GPIO.LOW)
   
    print('DIR set to LOW - Moving Forward at ' + str(delay))
    print('Controller PUL being driven.')
    for x in range(durationFwd):
        GPIO.output(PUL, GPIO.HIGH)
        sleep(delay)
        GPIO.output(PUL, GPIO.LOW)
        sleep(delay)
    GPIO.output(ENA, GPIO.LOW)
    return
   
tk = Tk()
tk.geometry("400x300")
b1 = Button(tk, text="Relay On", command=Relay_on).place(x=100, y=50)
b2 = Button(tk, text="Relay Off", command=Relay_off).place(x=100, y=100)
b3 = Button(tk, text="Exit", command=Exit).place(x=100, y=200)
b4 = Button(tk, text="Forward", command=forward).place(x=100, y=150)
tk.mainloop()

GPIO.cleanup()
#