[AliSintax]

Hello, I’m doing tests and I notice that the Art4 motor loses steps (skids) when trying to move. I have configured VRef in the A4988 Driver with VRef 0.4 (which is something more than: 0,4A x 8 x 0.1), and also I have increased it to 0.8 , but the same thing happens (the motor jams without strength by hand). Am I missing something?

Thank you and greetings.

Spanish: VRef para los drivers A4988 (sobre todo oara la articulación 4)

Hola, estoy haciendor pruebas y noto que el motor de la Art4 pierde pasos (patina) al intentar moverse. he configurado VRef en el Driver A4988 con VRef 0.4 (que es algo más que: 0,4A x 8 x 0.1), y incluso he subido a 0.8, pero sucede lo mismo (el motor lo trabo casi sin esfuerzo con la mano). ¿Se me estará escapando algo?

Gracias y un saludo.

[Angel LM]

Hello AliSintax!

You are using the same stepper model for articulations 5&6, right? If so, you are experiencing the same issue with those steppers?

I can think in 3 possible issues:
1. Maybe the art4 driver is broken and is not working well. To check it just switch the driver with any other and try to move the motor.
2. The wires of the stepper are not well connected. Sometimes the manufacturer messes up with the position of the wires in the connector of the steppers. They should be placed in order: 1A1B2A2B. A quick way to check the wires is, with the motor disconnected, connect a wire between two of the motor connector pins. If you try to turn the motor shaft by hand and it generates a higher resistance than when the wire is not connected, it means that the pins you have connected correspond to the pins of one of the coils (1A1B) for example.
3. The max speed or acceleration value is set too high. Check that the $parameters match with the ones posted here.

Hope it helps!

[AliSintax]

Hello Ángel, thanks for the feedback.
Yes, joints 5 and 6 have that same stepper model, and I have connected the Art4 one to driver 1, 2, 8…. The wires are correctly identified in this case (measured with a multimeter), and in fact, in no load the motor rotates (with little force but rotates).

I have investigated other montages like this: https://www.youtube.com/watch?v=OvImX71rMhQ (minute 10’50”) to verify that VRef is correct (in case it happens to others, i leave the link). I have even tried another model of stepper with greater torque, because I tend to think that it is the mechanics of that Art4, and its bearing, because although I test by hand after many adjustments it runs smoothly, then from below, which is where the motor engages, it gives me the impression that is no longer going so fine.

The firmware is yours original, regarding speed, acceleration and steps values, so I understand that I should discard that part, but I will continue investigating,but I think that in my case it is the mechanics of that joint.

As I said, very thank you for your feedbak and for your great project!!

All the best.

Spanish:
Hola Ángel, gracias por el feedback.
Si, las articulaciones 5 y 6 llevan ese mismo modelo de stepper, y el de la Art4 lo he conectado también para probar en al driver 1, al 2, al 8…. Los hilos están correctamente identificados en este caso (medido con multímetro), y de hecho, en vacío el motor se mueve, es decir gira (con poca fuerza pero gira).

He investigado otros montajes como este: https://www.youtube.com/watch?v=OvImX71rMhQ (minuto 10’50”) para verificar que VRef sea correcto (por si os pasa a otros os dejo el enlace). Incluso he probado otro modelo de stepper con mayor par, porque tiendo a pensar que es la mecániza de esa Art4, y su rodamiento, porque aunque pruebo a mano tras muchos ajustes va suave, luego desde abajo, que es donde engrana el motor me da la impresión que no va ya tan suave.

El firmware es el tuyo original, respecto a valores de velocidad, aceleración y pasos, por lo que entiendo que debo descartar esa parte, pero seguiré investigando, pero pienso que en mi caso es la mecánica de esa articulación.

Lo dicho mil gracias por tu feedbak y por tu gran proyecto!!.

Un saludo.

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