ACORN 0-10VDC output to VFD always has residual voltage

[AnnArborNate]

Good day folks. I have spent the last day or so getting my Tree 425 Mills spindle VFD hooked up to Acorn.

I have the spindle functional, reversible with M3/M4 and I have preformed the spindle tuning and everything works fine except for the fact that the Acorn 0-10VDC output never truly goes to 0VDC. Thus, I have an issue with my VFD commanding spindle "dither" when supposedly at spindle stop.

I tried adjusting deadband on this 10HP baldor durty duty VFD. Sadly, the only deadband adjustment I can find is for a digital input and that is not the 0-10VDC analog input I am using to take in the voltage for the purposes of speed control.

Any chance someone has seen this before? I tried searching google and the forum here and I did not see anything that speaks to this residual voltage issue.

Please forgive my use of terms. I am not a professional, so I may get things a little confused.

Thanks,
Nate.

[ShawnM]

Do you have the .1 mfd cap installed on the Acorn? I'm not familiar with your VFD but on most you cant set a minimum RPM and this will ignore any voltage signal below that RPM.

[AnnArborNate]

I believe the board is a version 4.

Where/how can I check for this .1mfd cap?

[Centroid_Jacob]

Hi Nate,

You would have to purchase a 0.1 mfd capacitor online or from a local store that has them in stock. You can see the post from tblough for a little more information. https://centroidcncforum.com/viewtopic.php?p=33608#p33606

[ShawnM]

As noted, if you didn't install one already it's not there. Buy a .1 mfd ceramic cap and insert it in the across the header on the Acorn analog output along with the wires you have running to your VFD. Just insert one end of the cap in one terminal and the other end of the cap in the other. No need to worry about polarity.

My caps look similar to this one.
https://assets.alliedelec.com/f_auto,q_ ... 095129.jpg

This would work:
https://www.mouser.com/ProductDetail/Vi ... gL2jvD_BwE

[cncsnw]

Adding a capacitor is not a bad idea.

However, if your spindle is "dithering" or drifting when it is supposed to be off (i.e. after an "M5" or Spindle Stop command, not to be confused with "M3 S0"), then your spindle drive is remaining enabled.

You cannot control the spindle solely with the analog voltage. You also need relay outputs for run-forward and run-reverse.

If neither the run-forward nor the run-reverse relay is closed, then the spindle drive should be disabled. When the spindle drive is disabled, the motor will be free (no power, no torque) regardless of what residual voltage may be found on the analog command.

[AnnArborNate]

Well folks, I have things pretty much figured out with your help now.

I have the VFD under acorn control with 0-10v. I have spindleOk enabling the VFD. I have M3/M4 running relays correctly. and also spindle stop and start is correct.

Next up is to wire the contactor for the VFD power input to the Estop switch such that Estop will kill coil power on the VFD power contactor. Thus completely depowering the VFD with Estop switch activated (2 sets of contacts both normally closed(one for Estop and one for VFD power contactor coil))

Thanks SO MUCH for all your help!