[RéSOLU] Steppermotor moves erratically when DMX value is ramped up slowly

[Micropuller]

When I set the motor to "inverted" instead of "uninverted", the problem with the back and forth motion is gone.

[Jacques]

I tried to reporoduce but my test motor canot run such speed.
https://www.omc-stepperonline.com/downl ... _Curve.pdf
2400rpm is a very large value for a stepper motor, it is not visible in your case because of the gear.
Please give me the references of your motor and your driver.
Anyway, my motor seam to work correctly with Revolution/minute min : 100, max : 750

As I told you, I'm going to rework the stepper part of the arpschuino32 firmware. I'll start at the end of January, it will be the occasion of a big cleaning

[Micropuller]

My motor is this one: https://www.omc-stepperonline.com/nema- ... 1684s-pg27
The drive I'm using is an older Leadshine model (M542 PbF-G): https://www.manualslib.com/manual/13038 ... tml#manual

At first instance, I tried to insert the largest number I could, without the configuration tool throwing an error.
When I had it set at 2400rpm max, I couldn't ramp the speed value all the way up to 255, because the motor would stall. I had it at about 150 (58%) max.
Now I have the rpm set at min: 50, max: 550 (so I can use the full DMX range).
At those values the motor exhibits the same behaviour.

[Micropuller]

I have been looking at the stepper code and the arpstepper library, but I'm afraid my Arduino coding skills aren't nearly sufficient to try and troubleshoot this, let alone help you to rework the library.
It would be nice to have the possibility to add a home switch (and / or limit switches) and possibly a ramp up / ramp down function.

I'd like to be able to use the arpschuino to control animatronics using DMX.
Up untill now, I've used several boards that can control one stepper motor, but it would be really convenient to have one board that can control several motors at once and maybe even relays and led's at the same time!

[Jacques]

Ok so you arrive at max speed values comparable to mine.
It is normal that the interface did not send you an error message because these are not values that cannot be reached by the processor but by the stepper itself. If you had set for example the same values but with 1800 steps per revolution, you would have had an error message.
I have a question: is your driver OK to work in 3.3v?
In fact, feedback from users like yours helps us a lot to progress.
When I will rework the stepper part of the arpschuino32 firmware from the end of January, I plan to start with speed management and then I will tackle the input part in order to integrate limit switches or things like that. Lot of users are waiting for it !
This is all going to take some time and I will post an update when everything will be ready. But if you are interested you can become a beta tester and test the evolutions as you go.

[Jacques]

Another question :
Which value are ramped? speed? position? both?

[Micropuller]

Where the control wires connect to the drive it says "pul+(+5V) and "dir+(+5V).
In the manual it says that a signal >3.5V will be seen as a high level and a signal >0.5V will be seen as a low level.
So 3.3V might be questionable.

Maybe this is also of interest:
(1) ENA must be ahead of DIR by at least 5μs. Usually, ENA+ and ENA- are NC (not connected).
(2) DIR must be ahead of PUL effective edge by at least 5μs to ensure correct direction
(3) Pulse width not less than 1.5μs
(4) low level width not less than 1.5μs

[Micropuller]

Another question :
Which value are ramped? speed? position? both?

I think it would have to be position? When using a (stepper)motor to drive a mechanism, it is very desirable to have the possibility to gradually increase and decrease the speed of the motor at the start and end of a stroke. It prevents exessive loads on the drivetrain and makes for a more elegant motion.
I guess for an application where you have the ability for "live" control (not pre-programmed), it would have to be something like a minimum amount of time it should take to step up or step down the parameter that sets the position?
At present, when the DMX value is changed, the motor will try to reach the new set position as fast as it can. What you'd want is for this change to be more gradual.
Maybe by introducing a delay between writes that can be set by the user?

[RitoonL]

Hello, in fact,

while re-writing or updating the stepper library (Next in Todo list), it would be cool to add a customizable acceleration tab, as we can find on 3d Printers. i think we can find some part of code as exemple in open source 3d printer software like Marlin. if i remember well, this is a square curve, as the unit is usually in mm/s².

We can find some code somewhere here : https://github.com/MarlinFirmware/Marlin i tried to inspect where the code bit is, but did not find it yet.

@jacques we already talked about that times ago, i think this would be a good timing to work on this and implement this in the stepper library !

@micropuller we are happy to have users like you, it pushes us to improve every day, actually, we need feedbacks like this, i'm sorry that you will have to wait until all this is ready, we're a very small organization and all the updates and projects have to be chosen carefully because of little effective work time we've got. All we would like to do would require full time staff that we don't have !

Please be patient, we'll make all this work.

Regards,

Eric

[Micropuller]

Thanks Eric!
The Arpschuino has a lot of potential and I can see a lot of usecases for it.
At the moment I'm really in need for something that can drive a steppermotor (preferably more than one) using DMX. The only thing I really need to get to work is the homing (I thought I had it figured out, but unfortunately not 100% yet, see my other thread).
It's really nice being able to configure the settings throught the webpage. It makes setting things up just right much easier and faster.
Great work so far!

Cyril.