Axbbe/uccnc pwm unstable problem

[livinico]

Hello everyone, I turn to you to solve a very annoying problem related to the pwm (Ao1) I have correctly set all the parameters as described in the manual, despite this I find the output unstable and fluctuating which causes the spindle speed not to be precise. To give an example, if I set m3 s8000 I find myself a spindle that has about 7600/8400 revolutions causing an annoying continuous hi / lo not always the same and not with the same repetition frequency. I used the common 5v0 as gnd and correctly wired A01 from the controller to the spindle driver. Am I doing something wrong? Thank you.

[ger21]

Have you measured the actual voltage from the output?
I had this issue with a Huanyang VFD. The problem was the VFD, not the analog voltage.

[eabrust]

Is spindle PID control enabled with settings that don't work for your setup?

regards,

[livinico]

At the moment i use the ws55-220 driver, he drives a simple 400w brushless motor that is easily cheap and available on the network, as standard he was equipped with a potentiometer to manage the RPM but it was also possible to manage externally with a pwm. Through mach3 and different control card I didn't have these problems to manage it. The AO1 output measurement is correct (0-10). However, if I take advantage of 80% at the output, instead of finding 8v, for example, it fluctuates 7.7 / 8.3 causing the annoying hi / lo in the ear.

[livinico]

Is spindle PID control enabled with settings that don't work for your setup?

regards,

The pid is disabled as it is a spindle with only pwm input. Regards.

[livinico]

Update 08/02. I managed to solve the problem almost completely by adding a new mass from 5v0 to the driver that manages my spindle, finally I inserted a 100nf (104) ceramic capacitor between the gnd and the pwm. Now I find a much more stable voltage with an oscillation of revolutions not exceeding 50rpm eliminating the annoying hi / lo. Hope this post will be useful to someone. Thank you and good evening.

[CNCChris]

Thanks for posting this as I am having the same problem,

So you put a 100nf between AO1 and 5v0

Also you mentioned putting a mass between 5v0 and driver, what is a mass?

[thegreatwaldo]

Masse is German for earth.
Cheers
Andrew

[cncdrive]

Yes, you should link the 5V0 and the VFD's analog ground together properly, if that wire is thin could cause problems like what you experiencing.
Also add the capacitor possibly at the VFD analog input side.
100nF is not much, it is great to reduce high frequency noise, but if the voltage is fluctating relatively slowly and/or with a high amplitude then my advice is to use a much larger capacitor, e.g. 100uF or so.
Ofcourse you could keep the 100nF ceramic in parallel, because as I wrote it filters the high frequency noise really well.