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Author Topic: G540 No PWM Signal  (Read 2708 times)

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Offline kolias

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G540 No PWM Signal
« on: February 05, 2017, 01:29:22 PM »
I have tried various settings to get G540 to output the correct PWM voltage on terminals 7&8 with no success. (The 4 stepper motors work fine).

The first time I powered ON my Chinese VFD it was programmed for local control and the spindle started at very low RPM. Turning the speed knob had no effect on the spindle speed (spindle is water cooled and I can hear the VFD powered ON the water pump). But when I switched ON the power to the G540 it went to full speed in a second and I turned it OFF with my Estop to avoid damaging the spindle.

Reading on the web, someone suggested to first check the voltage on the G540 terminals 7&8. Doing that (with the wiring to VFD disconnected) I get between 0.09 – 0.12vdc with speeds M3S6000 to M3S24000) Changing the Mach3 settings to various combinations including the pulley settings from 0-24K and other combinations, the volts remain the same.

I used the Gecko 540BVFD.XML but now it has changed because of the various new settings regarding motor outputs, output signals and motor tuning but under Spindle setup on Mach3 I left the default settings in the motor control (Use Spindle Motor Control and PWM Control are checked, PWM Base Freq. = 50, Minimum PWM = 5%)

The G540 terminal 5 is connected the VFD FOR (terminal 6 is not connected to anything)
Terminals 7, 8, 9, ARE connected to VFD ACM, VI and +10V respectively
The water pump is connected to VFD terminals FA & FB (pump works fine)
The G540 terminal 12 is connected to VFD DCM plus to earth ground plus to the PSU negative (all separate wires).

Any ideas for help?
Nicolas

Offline kolias

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Re: G540 No PWM Signal
« Reply #1 on: February 06, 2017, 03:29:48 AM »
In the Ports & Pins menu, Spindle Setup, Motor Control, Gecko has set the PWMBase Freq to 50. Since my Spindle is rated 400Hz should this number be 400?
Nicolas

Offline dude1

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Re: G540 No PWM Signal
« Reply #2 on: February 06, 2017, 01:47:12 PM »
25

Offline kolias

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Re: G540 No PWM Signal
« Reply #3 on: February 06, 2017, 02:09:14 PM »
Can you please explain how did you get the 25, just to learn. Thanks
Nicolas

Offline dude1

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Re: G540 No PWM Signal
« Reply #4 on: February 06, 2017, 02:12:52 PM »
It was what I got told to use

Offline ger21

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Re: G540 No PWM Signal
« Reply #5 on: February 06, 2017, 03:36:40 PM »
PWM frequency has no relation at all to the spindle frequency. The Mach3 manual has some information on how the PWM works, and how to set it up.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline kolias

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Re: G540 No PWM Signal
« Reply #6 on: February 06, 2017, 04:05:56 PM »
Good to know this Gerry, thanks but the Mach3 manual pages 5-12 and 4-19 do not say how to find out the PWMBase Freq number to use on the Spindle Setup /  Motor Control. They just show an average width of the signal at 50% and 20% width.

According to the manual it says if I have a motor with a speed of 3000 RPM then using the signal shown in figure 4-14 would run the motor at 3000x0.2=600 RPM. In my case if I use the above numbers with my 24K RPM spindle 24000x0.2= 4800. This number does not make sense to me
Nicolas

Offline ger21

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Re: G540 No PWM Signal
« Reply #7 on: February 06, 2017, 06:10:09 PM »
The base frequency is an arbitrary number that you pick.
Dividing the kernel speed by the base frequency will give you the number of speed steps that you'll have.

With a kernel speed of 25,000 hz, and a base of 50, means you'll have 25000/50 = 500 different speeds, from 0rpm to max rpm. The actual speed range is set by configuring your pulley speeds.

The actual frequency is dictated by the S word in your g-code. If your g-code commands the spindle to spin at 24,000 rpm, then you'll get a 100% frequency.
The manuals example of the frequency at 50% is what you'd get if you commanded an S12000.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline kolias

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Re: G540 No PWM Signal
« Reply #8 on: February 06, 2017, 07:06:58 PM »
That's all clear now Gerry and much appreciated
Nicolas

Offline kolias

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Re: G540 No PWM Signal
« Reply #9 on: February 15, 2017, 05:21:57 PM »
What is your experience with the "Mach3 plugin for Huanyang VFD"? It uses an RS485 USB adapter and made by Leroyaumedeole.
Nicolas