Quote Originally Posted by shinytooth View Post
Thank you for the replies.

Mactec54, the board that you suggested is one of the boards that I have tried, it's the one that lands me within roughly 500 RPM of the target speed. I have been able to measure the discrepancy to about 200 millivolts and my oscilloscope shows a very clean DC voltage. I suppose 500 RPM is only about 2% of 24,000, it just sounds like a lot to me. I don't believe that my VFD is a genuine Huanyang. My particular VFD does not directly support a 0-5v analog input; however, you can adjust a "max voltage" setting between 0 and 1024, but 1024 always equates to 10v. Adjusting the min and max to somewhere around 10-980 does get me a little closer, but not by much. At this point, I think I might be splitting hairs.

I looked into controlling the VFD with RS-485, but I don't believe that my VFD is a genuine Huanyang. Tearing it apart, the PCB appears to have RS-485 IO, but there are no screw terminals and the manual says little on the topic. Maybe that is something to play with in the future, but for now I think that I am going to stick with the PWM to analog board that Mactec54 suggested. If anyone is curious, the VFD model number is "YL620-A-1.5KW" and has no brand name or manufacturing information. But hey, it was cheap and the spindle cuts well .
That board has pots that you can adjust to get your RPM closer, first adjust the PWM to get the 5v then adjust the 0-10v output

A YL620 is not a Huanyang VFD Drive post a photo of the terminals