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tommylight wrote:

@RDA,
Do you have a high voltage/high frequency pilot arc plasma cutter with CPC?
Open it, se where the voltage is taken from, then come back and edit your last post.
As far as I know the MAXPRO 200 is a high frequency/high voltage start machine
That means on starting, there are many thousands of volts flowing around.
Ther are photos on this forum of a THCAD that has been subject to these voltages and burst into flames on a much smaller machine where the torch voltage was picked up in front of the HF start module.
What Tommy is saying is you must connect the THCAD behind the High frequency module to avoid joining this example of what not to do. 

Sorry I somehow missed this one. As I don’t know how the pcb is made and don’t know how it breaks I can’t say much about it specifically.

I just wanted to note that the HF is not formed between the electrode and work. It would be nearly impossible to push the spark made by the HF unit, being it a spark gap, electronic or any other type of ignition unit, from the electrode to work. The distance is far to big and trying to push it through the nozzle would not work.

The voltages present between work and electrode during the ignition phase (typically sub 100ms) are mostly, if not all, induced voltages and these are in the MHz range (much like ohmic sensing).

The pilot voltage is pretty much the OCV and is typically under 300V.

My best guess would be that the divider resistors are your standard resistors and not pulse withstanding as they should.

I’m sorry if people feel like I am trying to argue, it’s not my intention. I just try to ”demystify” this as there are no magical forces involved in here.

tommylight wrote:

@RDA,
Do you have a high voltage/high frequency pilot arc plasma cutter with CPC?
Open it, se where the voltage is taken from, then come back and edit your last post.

As far as I know the MAXPRO 200 is a high frequency/high voltage start machine
That means on starting, there are many thousands of volts flowing around.
Ther are photos on this forum of a THCAD that has been subject to these voltages and burst into flames on a much smaller machine where the torch voltage was picked up in front of the HF start module.
What Tommy is saying is you must connect the THCAD behind the High frequency module to avoid joining this example of what not to do. 

The most accurate way to measure analog voltage would be to use the Mesa THCAD  attached to an encoder input. 
The THCAD is a voltage to frequency converter so the frequency is scaled in HAL to a voltage (or more likely distance in your case)
You can choose 0-10v or 0-5 volt ranges on a THCAD2. I was able to see the voltage ramp up over 0.04mm as the probe contacted the plate in a 24 volt circuit. refer to ohmic.comp component

mariusl wrote:

This morning LinuxCnc does not connect to the board and the error is that it cannot retrieve the MAC address.

I am pretty sure i see that often, but that is not the error or the issues, it is a warning and it continues and works as it should.
What does the error report say?
what is the result of
ip a
-
I have over 10 of 7i92 in daily use, some for over 7 years i think, some on industrial machines, never had a single issue.
Mind you, some are used on plasma machines with no BOB, one pin connected directly to THCAD on the back of the plasma source with 6-10 meters of cable, all plasma's have high frequency pilot arc, and still none of them failed.

Grrrrr I lost my post..
Darn, that just happened to me too. Had a whole essay for you
I appreciate being able to bounce my thoughts off you and the forum. Really helps to firm up my ideas.
I found your video about the variator. I had watched it once before (on page 32) What is actually the back gear ratio? 1:7 or 1:6.5?
Thanks for picking that Up. I said 1:7 from memory (failing). It is 1:6.5

At your high speed, what is the variator RPM range? eg something like 2200-3000 RPM = 800 RPM range?
The variator has much more authority. More like 1:4 ratio change range.

What is the variator actuator travel distance? Is it linear?
The linear screw, acts through a bellcrank on the spring loaded pulley sheath. There would be some non-linearity in the rotational motion of the bellcrank, but that is irrelvant given the non-linearity of the belt riding in the pulley, slip, belt wear, thermal expansion etc. The speed verses actuator relationship is probably ideally quadratic or exponential though. It is not linear.

I am wondering if you couldn't use one of these to sense variator position?
thesensorconnection.com/product/shock-ab...potentiometer?v=3003
We just need to work out how to sense the resistance value. A mesa THCAD could sense the voltage change with resistance very accurately if you have a spare encoder input.
I also started off with ideas about servo control of the variator. This could be done, but is unnecessary. The variator ratio changing through a 3Ph motor means that the rate of ratio change is constant. I could only alter and control that rate by replacing with servo or stepper, or approximate it with bang bang control. Given the wide range of speed control by the VFD, I dont need to finely control variator ratio. It take 5 sec to drive the variator from one stop to the other. Using 5 one second pulses, counting how many have been given gives me a 5 speed gearbox. Or with  half second pulses, it is a 10 speed, closer range gearbox.
The encoder closed loop VFD control  can deal with all the speed change between ratios.

Since it is a lathe, on CSS cuts, the spindle rpm needs to be constantly changing.

Plan A
Home the variator to an end stop on start up. Afterwards keep track of variator gear ratio by counting gear changes.
At a spindle on command, decide on high or low gear. Set it. It is fixed till next spindle stop.
Start spindle, set the variator to the lowest ratio closest to the commanded speed. Once the spindle is on speed, continue with the program.

As the facing cut progresses, linuxCNC will be increasing commanded speed, and the VFD will be increasing frequency until it approaches its limit.
At that point command the variator to speed up for 1 sec. As the VFD has much more precise and responsive control, during that sec, as the variator changes ratio at it's fixed rate (most likely too quickly), the VFD will probably reduce frequency to hold spindle RPM.
After  the variator stops adjusting,  the VFD frequency will again increase, towards its limit.
Rinse and repeat up to 5 times.

I am thinking if you can sense the actuator position, you select the back gear, then assuming say a 50 Hz VFD frequency, get as close as you can get with the varistor, then trim it with the VFD. Let the encoder feedback act on the vfd.
Adding a varistor or LVDT is still not a measure of gear ratio. You could define a function to map that value to ratio, but it would be subject to the inaccuracies of bellcrank motion, belt wear, thermal expansion, slippage due belt contamination etc. Plus, there is really no need to such accuracy in variator control, as the VFD will  compensate automatically.

The back gear is easy. Before the spindle starts, either high or low. Since that can only be based on the first speed commanded, I need to consider in any CAM PP, to stop the spindle between different types of cuts, otherwise the gearbox can be stuck in the worng range. For a really large facing path, I need to either accept 800 rpm top speed in the middle, or break the cut into two parts and stop and change gear between cuts.

Makes my head hurt again!
You and me both, but a problem shared is a problem doubled

Speaking of head hurting, thinking about it, the  current variator ratio could be constantly calculated. Motor RPM / VFD frequency is proportional to input voltage, so the variator input rpm is knowable in real time.
The back gear condition is known and one of two fixed ratios, and the spindle RPM is measured by the encoder, so variator output RPM is also known, and thus current ratio can be calculated.

This could be helpful. The arrays as look up tables are used in your Comp to inform Linux CNC what overall ratio to is in use, so it can scale the mapping of VFD input voltage to RPM. If I can constantly calculate that value, no look up table would be necessary.

I suspect someone is going to pop in now to inform me that I will also need to vary the PID values, as those which work with an overal drive ratio of 1:1 are completely different to those that work with 1:90, roughly the Schaublins overall rpm control range.

Grrrrr I lost my post..

Yes, mine is a basic round column mill with 2 belts. belts cannot share the same level and buttons in the GUI are disabled to prevent invalid selection.
I used one of those laser tachometers to read spindle revs low and high on every belt position, then calculated the ratios from 6300

I found your video about the variator. I had watched it once before (on page 32)
What is actually the back gear ratio? 1:7 or 1:6.5?
At your high speed, what is the variator RPM range? eg something like 2200-3000 RPM = 800 RPM range?
What is the variator actuator travel distance? Is it linear?
I am wondering if you couldn't use one of these to sense variator position?
thesensorconnection.com/product/shock-ab...potentiometer?v=3003
We just need to work out how to sense the resistance value. A mesa THCAD could sense the voltage change with resistance very accurately if you have a spare encoder input.

vfdmod is the RS485 component I use to control the VFD forum.linuxcnc.org/24-hal-components/387...trol-over-modbus-rtu

To debug components, I usually add temporary debug pins named like debug-rpm and remove the later.

I am thinking if you can sense the actuator position, you select the back gear, then assuming say a 50 Hz VFD frequency, get as close as you can get with the varistor, then trim it with the VFD. Let the encoder feedback act on the vfd. Makes my head hurt again!
 

Hope everyone had been doing well! Been off here for a while, a bunch of life stuff happening, blah blah etc etc. Made a few 'upgrades' to the table recently. Also moved into a shop space where I have everything under one roof, including living quarters. I've been making simple artistic metal sign kind of stuff, and to my surprise that's actually a viable business around here. So before the table was not completely welded. Half of the joints to be welded were completed, just enough to get it up and running. Fast forward a couple of years later and I suspect some of my intermittent program stop errors had to do with table slop. Fortunately after some mearuments, found it to still be square and true. So I welded it all up and it's super rigid, pretty much no wiggle any more. Also modified the feet to be more solid, which seems to have helped with some slop/sway during rapids of 1200ipm.Relocated the electronics box to a more protected area under the water pan. Speaking of the pan, cleaned that out for the first time. Lot of weight removed from the table haha. Fixed a super slow leak in the drain while I was in there. Next round of upgrades will be to integrate the ohmic sensing (thcad-5). I've had the board and whatnot for a couple of years now, it's about time I got to using that stuff. 

Thanks. Am I understanding it right that the LFS-AP01 is similar in the plasma world to the dedicated torch height controllers that worked independently of something like LinuxCNC? And if that analogy holds, I think the potential is for the BCL-AMP to be analogous to the THCAD board, feeding a capacitance value into LinuxCNC by way of the velocity of an encoder input so that LinuxCNC can do torch height control via external offsets.

If that's the case I'm much more interested in getting the BCL-AMP to work, but information on that sensor has been hard to come by.

Thanks,

Scott

Please let me know if I shouldn't resurrect this thread, but instead ask somewhere else. I am starting in on a LinuxCNC fiber laser project, and am working with a BCL-AMP sensor. I was wondering if the correct pinout was ever conclusively determined for the 4 pin connector. 5V or 24V? Also is the sensor PWM or frequency output? It seems like it can possibly be used as a drop-in replacement for THCAD, but I believe a THCAD outputs frequency. I've never been able to find a data sheet on the BCL-AMP. I'm hoping since the time this thread dropped off folks have made progress on workable fiber laser LinuxCNC machines.

Thanks!

Scott

This is an oxyfuel cutting machine.
AND
"thcad.z-pos-out" connection?
"thcad.z-fb-out" connection?
 

Great work Alan. It's always good to see another plasma table come to life. And amazing that a Pi is doing the job for you.
Good idea to use the proma in a HF environment. Is that read by the THCAD?
a 48 V power supply might give better motor performance if your driver's can handle it. See how the cut quality is on corners and keep it in mind.

Unfortunately, the N2+ is on the back burner as it's in Leonid's hands. He says:
The state of my repository on github is not complete for building additional packages. After my last email, I decided to check my current work and push it to my repository, but I found an error in the algorithm. And now I'm making changes. I'll let you know when it's ready.

Last night I made my first cuts on my "home handyman" level plasma CNC table. It's still a messy experiment, but it's getting there. Thanks to everyone that helped me get to this point!

Here's a high level look at the build for the curious:

• Raspberry Pi 4 with PREEMPT_RT kernel
• LinuxCNC 2.9 + QtPlasmaC
• Mesa 7i96S
• THCAD-10 
• Proma voltage divider
• Reed switch for ARC_OK signal
• 24V Meanwell motor power supply
• 5V Meanwell logic power supply
• Ohmic initial height sensing circuit
• Shielded P-80 machine torch
• 40 amp plasma cutter with HF Pilot Arc
• Rails from OpenBuilds V-slot
• 3D printed plates
• Magnetic torch breakaway
• Belt-and-pinion X and Y axis drive
• Acme screw Z axis
  
  Once I can cut reliably I'll use it to make it's own aluminum plates. I also plan to swap the Raspberry Pi for an Odroid N2+ once rodw releases support for the PREEMPT_RT kernel.

Been searching but I just can't sort this one out.

I just recently got my machine up and running and finally cutting (including THCAD-10 THC).  Searching on this forum has been a godsend!   I have a working Xbox 360 controller jogging the axis etc.  I've also done some basic HAL signal - pin connections to get my indicators, latching E-Stop etc. all working again with many thanks to the collective wisdom here.

But I'm stuck on one thing.  I'd like to hook one of the Xbox controller buttons up to the "Laser" button in QtPlasmac but cannot for the life of me figure that one out.   Ideally this would allow me to jog and mark the edge/origin with my xbox controller without having to go back to the mouse to click the laser/edge/origin button in the UI.

I found the qtplasmac.laser UI button in Halshow and I can monitor that and see it going active when I click it with my mouse.   I can link a signal in HAL to the Xbox button (input.0.btn-b) and monitor that also in Halshow.   But how do I link that signal (or input.0.btn-b directly) to trigger the the qtplasmac.laser UI button?  That UI button goes through 3 actions;  laser on, set edge, then set origin.   Is this why I'm unable to link it?  

Hoping this is something basic I just missed in all my digging and if so I apologize for having to ask.  :/

-Dave

Just to clarify, I said "Surprisingly little info on plasma builds on most of the forums I follow", you both are making it seem like I said on this forum, I didn't and didn't mean to offend anyone.
I'm sure plasma is an active topic on this forum, but on other forums plasma builds seem to be years old, as I said. So I've been looking for "what's new" and that's what brought me back here.

Thanks for the links Tom, I skimmed so far, will dig deeper but it seems like most of what I saw is about the building of the table itself. As I said, I have the build done, just looking for the electronics part.
You suggested the 7196s, so I guess it's still considered relevant. I'll go with that one then. I'll look into the THCAD to see the model differences.
Any suggestions for an ohmic sensor? Just meaning is there any that will or won't work with LinuxCNC?

Here's a screenshot of my table. Found a design on youtube I liked so I modeled off that and made improvements as needed.
 

Mesa 7i96S and THCAD, several versions of THCAD depending on the plasma source.
Not sure where you got the stale info, but some companies started selling plasma cutting machines with LinuxCNC as a result of how good it has become for plasma.
Here are some loooong topic on building plasma cutting machines, one has also a full list of parts and detailed pictures of almost everything, 4 of those are in daily use for several years, 7 finished.
forum.linuxcnc.org/show-your-stuff/38547...plasma-build?start=0
forum.linuxcnc.org/show-your-stuff/32029...-plasma-cutter-build
Mesa boards
www.mesanet.com
www.mesaus.com