angle = input("Rotation angle in degrees: ")
step_count = int(4096/360*abs(float(angle)))  # 5.625*(1/64) per step, 4096 steps is 360°

if float(angle) > 0 :
        direction = True
        print("clockwise")
else: 
        direction = False
        print("anticlockwise")

Hah! if it works, it works. I’m glad this helped :).

Someone in the comments pointed out that this same motor is sold at various gear ratios. https://ben.akrin.com/driving-a-28byj-48-stepper-motor-uln2003-driver-with-a-raspberry-pi/#comment-840

I visited the linked website (http://www.4tronix.co.uk/arduino/Stepper-Motors.php). Its step sequence ends with [1,0,0,1], and begins with [1,0,0,0]. But this didn’t matter and the step sequence works fine either way.

The website also says 512 steps for 360 degrees. I don’t think the 8 phases of each step can be subdivided, so the stepper’s angular resolution becomes ~ .7 deg/step.

Am I understanding this correctly? It’s unnecessary I suppose. I don’t think this motor is suitable for applications demanding that level of precision. An integral proportion between steps and degrees would’ve been nice.

Hi Biel,
I guess your Pi doesn’t have enough power to make your motor run. You should use an external power supply (what is recommended to do whatever the motor, actually).

Hi Ben

Sorry for my late reply (been mothered with non playing wav files – all sorted now).

Many thanks for your swift reply and advice. I agree it’s a terrible way to incorporate your script. I’ll look into something else.

Thanks again – glad I came across your site.

Rik

I’d have to see your code, but importing the snippet I gave as a mean to run it seems like a terrible way to call it :). It’s not a library, it’s a fully fledged (albeit distilled to the essential) program that’s sets up the pins when it starts, and cleans them up when it stops. It’s not surprising it wouldn’t work when you’re calling it twice in the same context.

The thing to do here, is copy paste my code within your code, and arrange it so the “meat” section is a function you can call at will, ideally with a step count as a parameter.

I hope this helps.

Much appreciated

Rik

To answer your question more specifically about why the code doesn’t error out: it is doing what it is supposed to and activating the GPIO pins properly. From Python’s perspective, everything went well. There is no mechanism for it to be aware that this had no effect on the stepper motor or its driver.

Yes, the Pi can’t supply enough power. It can indeed supply 5V, but definitely not with enough amps. That’s why there’s an external power supply in the circuit. In general physical motion (motors) takes lots of power and doesn’t want to be powered by the logic. Another good reason is that motors often create massive interference on circuits and you don’t want them messing with the logic side, so it’s better to keep them decoupled from it.

I have the motor board powered directly from the raspberry, i execute the script and there is no error message, any idea why it executes but there is no movement from the motors or even the leds? Thank you so much.

Biel Paloamr

The short answer is yes. I’ve been running various projects for thousands of hours without missing a single step.

The long answer, and what you are alluding to correctly, is that Pi processors are shared between multiple processes and sleeping a certain amount of time between steps is not guaranteed. Here’s what I found though illustrated as an example. If I sleep for 0.0002 seconds between steps, it’s not guaranteed I’ll sleep exactly 0.0002 seconds, but it’s guaranteed I’ll sleep AT LEAST 0.0002 seconds. In the real world, when I hear my motors step, they have a very consistent sound, but if I SSH into the Pi and start running a bunch of commands competing for the CPU, I’ll hear the motors slow down at bit. Maybe that’s an issue for some projects with CPU volatility and where consistent motor speed being required. But it’s never been an issue for what I’m working on.

You can grab any of the available GPIO pins (https://pinout.xyz). Make sure to ground it too.

Thanks Ben,

I’m very glad to read your answer. In one of your videos I heard some French, so it makes sense with what you say regarding your sister. For sure she sould be Casteller in Paris or Toulouse.

USA is a great country, with more diversity than is transmitted through the news and stereotypes. Just a sample: I am writing this after attending a concert in Barcelona by the great Bruce Springsteen. I’m a big fan. He has always been a rebel and a committed man.

Concerning Catalonia, well,… just trying to preserve language ​​and culture, which is difficult in this globalized world if you don’t have a state behind. But always, keeping the doors open to everyone who needs it, with solidarity, There are millions of people who, just because of their place of birth, have less opportunities than us.

Best wishes to you and your family.

David,

bon dia, I was very lucky to spend several Summer vacations in Catalonia and I found it to be an incredible place. The culture is strong and the people are super nice. My sister is a Casteller in France, this tradition is exceptional and I show videos of it to my kids. Because they show amazing kids, but also because the exercise is the antithesis of American individualism :). It’s good for them to see both.

In any case, I won’t bore you with my vacations, but your place is a truly special one in the world, and from it there isn’t much to envy.

I’m glad I was able to help you drive your motor, and I’m suprised you were able to power the motor with the Pi :). Motors usually wreck havoc on circuits and you want to decouple them from the logic and other sensitive things. But hey, if it works it works :).

Take care and good health to you too.

What it’s more amusing is that I have descovered your web page. Congratulations. It’s fantastic. This lifestyle and projects are inspiring. They even make me a little jealous. Healthy envy. And they bring back a little hope in the human being. Good luck and good health from Catalonia.

there are multiple gear ratios for this stepper whilst his is most likely 1:64 yours is 1:16

Oh wow, I’m glad there’s an explanation. I never came upon the 1/16 ones, thanks for finding out.

I think that most stepper drivers have a “brake” mode that does draw current to stay in position, and a “free” mode that draws no current but lets the motor move is force is applied externally.