Author Options:

X is always happy Y is sometimes sad Answered

Hi One and All, New here and new ish to electronics. I have put together a physical test environment with a 450watt psu from a PC, an Arduino UNO R3, CNC Shield v3 - this is driving 3 dvd/cd rom drawer stepper motors via 3 A4988 drivers. Firmware uploaded as gbrl v09 using XLoader and running some test g-code using UCG. I have set V-ref on the drivers using a multimeter balancing motor function and heat. Well, there is in fact a very small voltage window where the motors work (.75 or thereabouts) the coils test at 10-11ohms.

The issue! X, Y, and Z axis all work perfectly when run individually. However, from a blog (can't recall which right now) I have created some polygons for the 3 axis to draw/print. X and Y motors won't run at the same time when the code dictates. X always runs and Y just shudders but when the code within the same file dictates motor Y to run alone it works fine. Z works fine irrespective of what X and Y do. I have tried adjusting v-ref to no avail. Does anyone here have any ideas how I can get Y to run alongside X? Thanks in advance.....


The forums are retiring in 2021 and are now closed for new topics and comments.

1 year ago

I would say you have a voltage-drop somewhere... A long and/or thin wire... 0.2 Ohm somewhere in a screw-terminal... It adds up. And as motors can pull quite high current-peaks, the combined current thru wire and terminals may cause a voltagedrop over the resistance.
As you mentioned, your Drivers work only with a very narrow voltage-window (Is that as it is intended and normal or is this also an indicatior of "weirdness"?). With small voltage-drops, the voltage may fall out of your working-window of those drivers...

These inputs are completely plucked yout of thin air and from the wording you provided. I dont have enough experience in Stepper-drivers and CNC-shields to be able to say "Jep. Thats this and that for sure. Had it many times. Fixed it with this all the time."...
So take it with a grain of salt. My input is based on basic electronics and thats often whats sufficient even as electronics engineer...