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Author Topic: VFD Spindle responds to S commands, but only sometimes.  (Read 1321 times)

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Offline Zaae

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VFD Spindle responds to S commands, but only sometimes.
« on: September 18, 2017, 09:25:10 PM »
Hi again everyone,

I've got another machine I've been working on, and I've run into a new problem I've never seen before.

If I start the VFD spindle, and issue S2300, the spindle speed goes to 2300. Issuing S4000 (or any speed for that matter) adjusts the spindle speed as expected, however any subsequent S commands do not change the RPM at all, and will not, until I turn the spindle off, and back on again, using the button, or an M5 command. The RPM slider also seems to become unresponsive at this point, as well.

I've verified that this happens not only when running the commands in MDI, but also running a test program. After two S commands (sometimes after just the first S command), the spindle stops responding to changes.

I updated Mach3 to the most current version, but the issue persists. I also hooked an oscilloscope to the VFD PWM output pin, and no change is being made to the signal by Mach3 when asking for an RPM change.

My next step is to start a new profile and re-configure everything, but before I go through all that, I thought I'd ask about it.

Any thoughts?
Thanks, Z

Offline ger21

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Re: VFD Spindle responds to S commands, but only sometimes.
« Reply #1 on: September 19, 2017, 11:25:28 AM »
I would think that the issue would be with your speed control/breakout board. Are you using the parallel port, or a motion controller? You need to  measure the PWM signal coming from Mach3, before it goes into your speed control, not at the VFD.

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