Mesa 7i77 config for two spindles

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10 Apr 2020 01:21 - 10 Apr 2020 01:24 #163430 by gmouer
Have a mesa 7i77 setup on my bridgeport cnc with a vfd controlled spindle. I just ordered a 24,000 rpm 1.5kw air cooled spindle with matching Hungyang VFD for use as a auxillary spindle for engraving and other such high speed uses. I will put the high speed spindle on as needed and run a separate config for each spindle setup.

What I have in mind is to parallel the 0-10V speed control output from the mesa 7i77 to BOTH vfd's. I am making the assumption that the 0-10V speed control input on most vfd's is a high impedance input and my proposal would not be a issue.

I will use the standard I/O lines for "run fwd" , "run rev" to each vfd, no sharing of lines/signals there. Only one VFD would be given a run command, the unused VFD would sit powered on but without a run command. I will have a separate config launcher for each spindle setup each with appropriate HAL and INI files for that spindle.

Is this a reasonable config idea? Alternately, what about using a unused servo channels 0-10V output and configuring it for the second spindle via some HAL and INI config lines?
Last edit: 10 Apr 2020 01:24 by gmouer.

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10 Apr 2020 15:00 #163489 by tommylight
VFD have their own 10V source for control, so version is out.
Version 2 might work, except do not connect the +10V on the VFD to anything and modify the hal to set the minimum output to 0V, not -10 as usuall.
Check if the new VFD has RS485, you can use that to control it, and leave the rest as is.

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10 Apr 2020 15:05 - 10 Apr 2020 15:06 #163492 by gmouer
Yes but VFD's internal 10V source is not used with mesa 7i77, the 0-10V is sourced from the mesa board.

The hungyang VFD does indeed have RS485 control capability and I have been looking at that. It seems like the easiest/best approach for my dual spindle setup. An added plus is that there appears to be a published component for linuxcnc to control hungyang VFD's with RS485, so most of the hard work is already done !

From what I have read, a USB to RS485 converter is the method used for the physical wiring interface.
Last edit: 10 Apr 2020 15:06 by gmouer.

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10 Apr 2020 15:34 #163500 by tommylight
Power both VFD, take a DVM and measure between same inputs on both of them, measure AC and DC, if you get a difference of over 2V in any case, no wiring together.
So, gnd on vfd1 to gnd on vfd2, and ref on vfd1 to ref on vfd2.
Do this while both vfd are on and motors spinning.

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