[mactec54]

Thanks for the insight, but I know how to use a scope!!!!

From what I read from all those references that were suggested prior to posting anything on here, was take the work clamp and go directly to the star point on the machine frame, then from there to the work piece/plate. Now that star point goes back to the grounding rod...

What that other post suggested was isolate that work clamp from the machine star/frame altogether.. From I gather to keep any stray hi freq out of the ground side. Probably not the safest thing to do because the plate being cut and the machine frame are now at different potentials which is the definition of voltage!!! But may get it going...

CR

Isolating the Ground Clamp will give you a Ground Loop, not something that is a great idea, but may work

Make sure your Power Supplies are isolated as well, that means +/- are floating, input ac Power is Grounded

You may know how to use an oscilloscope, it does not change the fact, the oscilloscope may not be able to handle the 10,000v dc @ 2Mhz blast that it may see

You can check your system without the Plasma Cutter running, just make sure the oscilloscope is off and disconnected before you run the Plasma part of the Machine

[ny_racer_xxx]

Isolating the Ground Clamp will give you a Ground Loop, not something that is a great idea, but may work

Make sure your Power Supplies are isolated as well, that means +/- are floating, input ac Power is Grounded

You may know how to use an oscilloscope, it does not change the fact, the oscilloscope may not be able to handle the 10,000v dc @ 2Mhz blast that it may see

You can check your system without the Plasma Cutter running, just make sure the oscilloscope is off and disconnected before you run the Plasma part of the Machine

Thanks for the heads up, I got it covered....

CR

[lens42]

Oscilloscopes aren't magical, they don't fix things by themselves...

If you read through what Jim Colt wrote, there's a lot of stuff the scope won't pickup, so it may or may not help, some of this is trial and error as it sounds like that's what Jim has been through and I respect that. Some of this eliminating noise is a dark science...

CR

Ah yes, things that are hard are "dark science". Sounds like the priests who persecuted Galileo. Yes, 'scopes can't do everything. OK, but I can't think of a better tool for this.

There are two mechanisms that cause these problems:1) conducted ripple/noise on supply or signal lines from loading or voltage drops on non-ideal conductors, and 2) magnetically Induced currents in wires, i.e through-the-air EMI, that make unwanted signal or supply voltage changes. 1 and 2 are VERY different problems and it's hard to fix if you don't know which you' chasing.

With a scope, you can actually see what is pissing off the the driver or computer because you will see all hell break loose on some signal or supply line when the arc starts. That puts you way ahead of where you are now.

I do this a lot (troubleshoot noise) and the key is to be methodical and avoid shotgunning.

Others' comments about risk to the scope are valid, so I'd use a battery powered one that can "float" and can look anywhere you want without worrying about it's earth ground.


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[ny_racer_xxx]

Ah yes, things that are hard are "dark science". Sounds like the priests who persecuted Galileo. Yes, 'scopes can't do everything. OK, but I can't think of a better tool for this.

There are two mechanisms that cause these problems:1) conducted ripple/noise on supply or signal lines from loading or voltage drops on non-ideal conductors, and 2) magnetically Induced currents in wires, i.e through-the-air EMI, that make unwanted signal or supply voltage changes. 1 and 2 are VERY different problems and it's hard to fix if you don't know which you' chasing.

With a scope, you can actually see what is pissing off the the driver or computer because you will see all hell break loose on some signal or supply line when the arc starts. That puts you way ahead of where you are now.

I do this a lot (troubleshoot noise) and the key is to be methodical and avoid shotgunning.

Others' comments about risk to the scope are valid, so I'd use a battery powered one that can "float" and can look anywhere you want without worrying about it's earth ground.


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I'm sorry, but with the exception of Jim Colt, seems to me everybody else knows about or less than I do about getting a plasma going on a CNC machine..

When Jim says sometimes they work, sometimes they don't, that's telling me they don't know exactly how to handle it, "they" meaning the experts....

I understand power supplies very well, I even put the control box on 100% DC power, so that pretty much eliminated any line issues...

[ny_racer_xxx]

OK Update:

I got the C10 from Automation on Saturday... I had to figure out the outputs to get the relay to fire the torch. The PC board I built with Opto's I was using the G540 outputs that go to ground when active. The C10 looks like it uses a TTL signal (5V) high, or (0V) low when active. Actually worked better, the opto's I have are switches, so the TTL signal turns them on and off, no need for an external relay or the 12V wall wart I was using to power the relay...

Hooked up the plasma, ground is floating right now, fired no problem a dozen times or so on the pilot arc through MACH3...

Switch the inputs from Pull Up to Pull Down, Proma THC seems to signalling OK....

Next thing I'm going to try is wire up the G250's that are in the G540 and get the motors running...

CR

[john-100]

which version of the G540 and G250 drivers do you have ?

the circuit of an early G540 taken from a post on cnczone ,
shows the positive supply for the opto isolators being taken from pin 26 marked do not use !on the G250 data sheet

early G540
Attachment 309350

G250 ver2
Attachment 309352


the latest G250 ver3 stepper drivers used in the latest G540 is not going to be easy to use with your new C10 break out board

I expect the G540 ver8 main board now has an additional regulator for the four HCPL-2531 opto isolators
freeing the G250 ver3 pin 26 to be used for the re located Anti-Resonance trim pots ( moved from the G250's to the G540 board)

John

[ny_racer_xxx]

Thanks for all your research!!!

A couple things though...

The drives themselves are NOT optically isolated, the schem is showing the isolation going back to the DB25 side of the G540.

The other thing I believe and I have to double check it, is that the pots are on the driver boards and there's a hole through the case to access it...

CR

PS Thanks again for finding that schem, I have the latest version of the G540, so it's a little different like the VFD analog 0-10V output, but looks similar enough...

That schem BTW looks to be everything but the drives, it shows the connectors to the drives though....

Looking at the schem, you can see all the signalling inputs and outputs are referenced from the ground on the DB25... Some of the issues could be related to the DB25 cable as somebody suggested, or the PC itself... We'll see...

I don't believe hooking up the drives will be an issue, I'm going work on the Z axis tomorrow..

I did find that RC servo plugs are the same .100" spacing that's the G250's, I have a bunch of them to sacrifice!!!! There's also an RC show in Jersey this Saturday, I'm going to and there's a company that makes those connectors in 2x5 format there, so I would need 3 of those per drive...

[ny_racer_xxx]

John-100 I found that thread with the schem.. http://www.cnczone.com/forums/gecko-...drives-75.html

Interesting reading.... 2500 PC Boards, $2000, that's $0.80 each, plus components and assembly, $81 each, that's some decent markup!!! They screwed up the layout, came up with a work around to "fix" them, then offered to sell these F'ups for $29 each... LOL

On the older schem there's a 78L12 chip, that's the 12V regulator, appears to be on the main board, that would take the 24V-50V and regulate it down to 12V...

[john-100]

Hi ny_racer_xxx

I found the G540 schematic in another thread
just read the one you linked to , it give some background info on how the G540 evolved I didn't know

as for PCB errors being corrected by wire links , Gecko are not alone

in the early 1980's I maintained Marconi mark 9 broadcast cameras , not only did they have wire links to correct errors - some problems being the routing of the signal earth paths , they also had added components mounted on added standoff terminals

at this time Ampex sold a kit for the user to replace two of the four sound channels on the VPR2 1" VTR with a two channel DolbyA board

a job not for the faint hearted as the machine cost about £50,000 in 1980 (£100,000 with the timebase corrector and monitoring bridge - { PAL monitor , oscilloscope , vectorscope and audio monitor} )



John

[ny_racer_xxx]

John-100, I found a video, might be on the home PC, I can't find it on this one, but it has what must have been one of those F'up boards.. You can see the jumper wires from the connector to the board trace..
Just sloppy....

Anyway, the G250x's in my machine are the ones without the pot on the driver board , but I wired one up and it does work!!! But not so good, stepper does chatter a bit, most likely because it doesn't have the correct value for the trim pot.. They are G250X V3

Look at the picture (red circle) and the pads are there to install the pots though....Attachment 309504

Anyway, for the few seconds I was moving the Z axis, it did get warm, not a good sign, probably going to bite the bullet and just buy some KL5056's...

Very happy with the way the C10 BOB works, gives more options, and I like 0V off, +5V on, instead of open and grounded...

CR

[john-100]

without the manual for the G250 rev3 its not going to be easy for any one to test one on the bench
without the circuit for the external trim pot


a while ago I used various photos and diagrams found on line including
Attachment 309508


to produce this circuit of the C10
Attachment 309506

one design error shown in the photo I found was some of the 74LS00 inputs are not connected !

I'm not sure how close it will be to the boards sold today


John

[ny_racer_xxx]

John, I had the rev 3 running on my Z axis wired as per the rev 2 manual. It's just not as smooth as it was when the G540 was running it. I suspect if I add a smd pot to those pads that are circled, it would work 100%.

I just don't think it's worth the trouble, I'd rather sell off the G540 to pay for the KL5056 drives...

CR

- - - Updated - - -

[ny_racer_xxx]

Here's a picture of what I believe was one of the F'up boards, don't quote me...

Attachment 309538

[UA_Iron]

I find it kind of amazing that someone with so many years of experience with these kinds of electronics systems has not consulted with the manufacturer for insight and support on such issues.

Interesting reading.... 2500 PC Boards, $2000, that's $0.80 each, plus components and assembly, $81 each, that's some decent markup!!!

Meaning that there are exists a statistical population of AT LEAST 2500 applications of this board and that thread was from 8 years ago. I am confident that the sample size has grown by an order of magnitude since then (25,0000 statistically similar models). People have successfully used these boards on plasma applications before. Gecko has been faced with similar issues before, I guarantee it.

And your numerical calculations don't take into account every other operating expense of the business, you have no insight to the "break even" cost, nor does it take into account the design and debugging time and then all the support Gecko has given on forums such as this one right here.

Oscilloscopes aren't magical, they don't fix things by themselves...

If you read through what Jim Colt wrote, there's a lot of stuff the scope won't pickup, so it may or may not help, some of this is trial and error as it sounds like that's what Jim has been through and I respect that. Some of this eliminating noise is a dark science...

Everything is quantifiable and approachable by a reasonable set of logic paths. The only dark science I see is in your approach. You presented a problem to a bunch of problem solvers and then tried to discredit them without attempting.

Literature pushes for equipotential bonding, IE shield frame grounded on both sides. Frame earthed. Read attached. It's a systematic approach though, so you must follow all recommendations or do something else (that requires black magic and voodoo or something).

Again, i'm not sure why you're wasting time digging into the details at a component level if you haven't tried the easiest solution first: contact support.

[ny_racer_xxx]

Yah, it's amazing.... But guess what??? I got it working 100% of the time without that hunk of crap Gecko G540...
Same exact everything as far as cables and grounding.....


I tried calling Gecko when the first G540 took a crap and you get an Asian gentleman that barely speaks English... All they want you to do is send it back for repair...

I know how to ground and bond, I tried every scenario BEFORE I posted a question, I read everything I found in here on grounding, including everything I could find from Al....

The problem is the G540 box, you can't shield it because they use it as a heat sink for the Mosefet's, so the only ground is through the signal ground, that's cheesy...

BTW what are they up to since that post? Rev 3? So that's probably at least 3 runs of 2500 boards at least, 4 boards per unit times $300 per G540, that's $562,500 in 8 years, at least... I happen to be a business owner and basically you have to operate on 100% markup to keep the lights on... So that's almost $70k a year in profit just for that product at minimum. Not too shabby, probably could have spent $5 bucks and make them less cheesy...

And I'm not trying to discredit anybody, there was some really good ideas and things I hadn't tried, but then it got down to desperation and I'm not just trying things for the hell of it....

Anyway.... I do appreciate everybody's input as I've said before, the box is just not very durable for lack of a better word for this type of plasma machine. Perhaps if I had a better plasma machine, it would have been fine...

CR

[ny_racer_xxx]

But I digress....

So, I finally finished most everything up, I got the C10 BOB, and Kelling KL5056 drivers hooked up.... Some confusion over the dip settings, they seem to be opposite than the literature...
But they are now humming along....

I like the 5V TTL on the BOB, I can run the solid stated relays, (LRD's) directly from the 5V for the outputs, no need for an external PSU.

So I have 1/2 of one SSR that turns on the torch, and the other 1/2 connected to a coil relay that connects the torch tip for the probe.

The machine seems to be working fine, does it's touch off, starts the pilot arc, makes the cuts, never a peep...

The only issue I have is I don't have any spare inputs for the prox switches...

What I'm thinking about doing is using another SSR to turn the power on and off to the prox switches, and just activate them at start up to square the gantry and set my soft limits.
This way I can share the same inputs as the THC.... And at some point upgrade to a smooth stepper, and be done with it...

Here's some pieces I did today, the back sides without cleaning them up, 12ga plate, 50a, @ 1600mm/min aprox, 63in/min, not lightning, but quicker than by hand!!!!

BTW old nozzles and electrodes also...

Attachment 311354Attachment 311356Attachment 311358

[ny_racer_xxx]

Burned up most of a 2x4 1/8" plate... Only hiccup was when the torch drop in a hole and the pilot was firing constantly, locked up Mach3. That happened once in all the cuts...



CR

[xjdubber]

Are you clamping your work ground to the plate at all? Cant imagine the way the work ground is hooked up that the plate is grounding very well.....

[Jon.N.CNC]

Glad to hear you got it working.. Really not a good for a popular company like gecko, It's basic practice to earth the enclosure you put your drivers etc in. To connect the gecko case to common ground not earth, if im understanding you correctly, beggars belief.