The charge pump frequency is 12.5kHz.?

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Cheers,

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Hi Peter,

The PMDX-126 doesn’t change.? And it's the one tripping the ESTOP.? Looking at the lights I can see the Charge Pump (pin17) light come on along with the ENABLE.? The moment the ENABLE comes on the AC Servo is energized and then they both go off and the RED ESTOP LED comes on at the other end of the PMDX-126.? So I'm guessing it's something to do with the Charge Pump output from MACH3 being different from the Charge Pump output from LinuxCNC which uses one of the stepper motor driver channels as a Charge Pump. ?

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The LinuxCNC is

# MESA 7i92H P2 connections

# ---Chargepump StepGen: 0.25 velocity = 10Khz square wave output---

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I can't tell from the parallel port version hal file what the charge pump frequency is.? I'll ask on the LinuxCNC group.

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Does anyone know what the Charge Pump frequency for MACH3 is?? Maybe it's not a square wave?

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As I said before, preventing the AC Servo switching noise from coupling onto the parallel port cable? solves the problem and these things are incredibly hard to diagnose via emails or even phone calls. ?Separation is our friend in this case.

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Guess I'd better bring the scope back into the shop.

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John

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From: [email protected] [mailto:[email protected]] On Behalf Of Peter Homann
Sent: January-12-20 2:13 PM
To: [email protected]
Subject: Re: [MachCNC] Electrical Noise

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My first thought would be a differences in the settings or software algorithms for noise filtering.?

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Cheers?

Peter Homann - (from my mobile)

On 13 Jan 2020, at 8:11 am, John Dammeyer <johnd@...> wrote:

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I've been building up my CNC system for the milling machine using a PC with dual boot for both WIN-XP and LinuxCNC.? I'm using the parallel port for both at the moment since it's easier to switch between OS and CNC software than unplugging a MESA board and plugging in a USB Smooth Stepper.

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The system is constructed as follows:

Parallel Port to PMDX-126 BoB

Separate 24V switching power supply for logic with a linear regulator to 15V for the HP_UHU DC Servo drives which run off 105VDC Toroid based power supply. ?

Axis X and Y are 3:1 and 4:1 with the 225 oz-in Brushed DC Servo motors.

Axis Z uses one Gecko running a 1200 oz-in motor on 65VDC toroid based supply for the milling machine knee (3:1)

Axis A uses a Harmonic Drive with an AC Servo STMBL drive using the same 105VDC supply.

Changing from the single phase 2HP (1.5kW) spindle motor to a 1.8kW Bergerda AC Servo but for now on the test bench using a 400W Bergerda AC Servo.

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There are several custom boards to do optical level conversion between the non-optically isolated PMDX-126 and the STMBL and also the 0V-10V PWM converter module from China.

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So here's the interesting problem.? Without the Bergerda AC Servo (spindle) motor powered MACH3 and LinuxCNC boot and can run/jog the various axis without issues.? Faults like encoder cable missing, high voltage errors etc. are all caught and cause the system to enter the RESET fault state.

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Plug in the Bergerda AC Servo (just the 400W unit) and suddenly MACH3 won't come out of ESTOP.? Reboot into LinuxCNC and absolutely no problem.

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Since this stuff is all running on the bench at the moment the solution turned out to be deceptively simple.? Move the AC servo motor away from sitting beside the PC and that moves the cables so they aren't lying along side the parallel port cable.? Now MACH3 comes out of reset without the PMDX-126 suddenly flagging an error and going back into ESTOP mode.?? Still works perfectly in LinuxCNC.

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I can now easily run a

S3000 M3

M4

M5

Using the MDI and the Bergerda works perfectly turning 3000 RPM? (200ipm).

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The DC Servo X axis (250 line encoder) with the 3:1 and 5 TPI lead screw configuration run a nice 200 ipm (Motor 3000 RPM) and the arrow keys nicely change direction between -3000 RPM and +3000 RPM as indicated by the Bergerda AC Servo Drive.

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All is as it should be!

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What I'm wondering is why it worked with LinuxCNC and not MACH3.? It was tried with Charge Pump ON during RESET.? No real difference.? Cycling it back on when it did work (although flakey) required using the OFFLINE button and the RESET.

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Remember, the only difference between the two systems was which OS was chosen when the PC boots.? No hardware was touched or moved during these experiments.

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The only thing I can think of is that the noise from the AC Servo was coupled onto the parallel port line and somehow the Charge Pump signal was corrupted in a way on the MACH3 system that didn't affect the charge pump signal generated by LinuxCNC.? A missing Charge Pump is the only thing that would cause the PMDX-126 to suddenly reset.? Especially since I had the FAULT signal into the PMDX-126 disconnected.

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Under LinuxCNC I can specify the Charge Pump Frequency.? I haven't found anything in the MACH3 setup that lets me set that.? There's enough switching noise in the system that looking at the signals with a scope didn't show anything specific.? The scope leads themselves were picking up noise and it's hard to determine where to connect the scope ground.

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Comments?? Why LinuxCNC robust.? MACH3 not??? Something odd with PMDX-126 setup that causes a Charge Pump Missing reset?

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Thanks

John Dammeyer

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"ELS! Nothing else works as well for your Lathe"

Automation Artisans Inc.

www dot autoartisans dot com

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