[punisher454]

I'm in the process of converting an old Moog Hydrapoint to a brushed DC servo system and was very seriously considering running Mach3. But I read that EMC will do full closed loop servo control. This sounds real good to me, but I have a few questions that I haven't been able to find real clear answers to yet by searching.

1. Am I correct in thinking that I can use an H-Bridge with a PWM and Direction input to drive each of my motors. I was looking at Dugong's, but I can make H-bridges myself easily(done it before several times). And I assume that a PWM signal can be output from a Mesa card, correct?

2. I am a big fan of multiple monitor setups, and custom GUI's. Will I be able to use dual monitors? I keep reading about problems with Nvidia drivers, will ubuntu allow me to span the desktop across 2 19" lcds with either a non-nvidia video card or an Nvidia card with different drivers?

3. I see that there is a newer version of ubuntu that the older one that seems popular for use with LinuxCNC, is there a problem with the newest version?

4. I have been planning to use a 2-3 HP sensorless vector VFD for my spindle motor. the lack of easy rigid tapping is a turn off to me for Mach3, but apparently LinuxCNC can. Am I correct to assume that I can still use a basic sensorless Vector VFD with the addition of an encoder on the spindle sending that signal to the PC and achieve rigid tapping capability?

Marvin

[samco]

1. Yes - linuxcnc software pwm and mesa hardware will both put out pwm+dir.

2. I am not sure with this.. You do not want to run closed source video drivers with linuxcnc though - So normally you would use the NV or VESA video driver. So whatever is available with those drivers.

3. The latest ubuntu long term support (12.04) does not have a realtime kernel built for it yet. Once that is done and tested - linuxcnc will be available on 12.04.

4. Yes - All you need is a 3 channel encoder on the spindle. (A,B and Z) Linuxcnc gears the axis to the spindle..

sam

I'm in the process of converting an old Moog Hydrapoint to a brushed DC servo system and was very seriously considering running Mach3. But I read that EMC will do full closed loop servo control. This sounds real good to me, but I have a few questions that I haven't been able to find real clear answers to yet by searching.

1. Am I correct in thinking that I can use an H-Bridge with a PWM and Direction input to drive each of my motors. I was looking at Dugong's, but I can make H-bridges myself easily(done it before several times). And I assume that a PWM signal can be output from a Mesa card, correct?

2. I am a big fan of multiple monitor setups, and custom GUI's. Will I be able to use dual monitors? I keep reading about problems with Nvidia drivers, will ubuntu allow me to span the desktop across 2 19" lcds with either a non-nvidia video card or an Nvidia card with different drivers?

3. I see that there is a newer version of ubuntu that the older one that seems popular for use with LinuxCNC, is there a problem with the newest version?

4. I have been planning to use a 2-3 HP sensorless vector VFD for my spindle motor. the lack of easy rigid tapping is a turn off to me for Mach3, but apparently LinuxCNC can. Am I correct to assume that I can still use a basic sensorless Vector VFD with the addition of an encoder on the spindle sending that signal to the PC and achieve rigid tapping capability?

Marvin

[punisher454]

Thanks for the response, and I have enjoyed reading about that K&T Conversion, these things inspire me.

Ok, I have made a little progress in the understanding of this, but now have some new questions.
First though, I have resurrected one of my old computers for testing. Its a celeron e1200 dual core which currently runs at 1.9Ghz. The mobo is an asus P5Q pro which I still like due to the all solid state caps and such (I have a stack of old motherboards with puffed up electrolytic caps). It has a basic Nvidia 8500GT card with dual head output. Memory is 2Gb ram (forgot the speed). And an old WD 250gb hdd.

Anyhow, after a fresh install from the live CD I was immediately pleased to see that the pair of LCD's I have attached both work properly spanning the desktop across both screens! I am not running the proprietary nvidia drivers, just the default that was loaded (I havent figured out how to find the driver info yet).

So running the latency test I get about 4500-5000 (stable for hours) on the 1ms test when idle. Loading glxgears and then other apps causes spikes up into the 25,000 range, while settleing down for several seconds in the 6000-8000 range and then spiking up again occasionally. If I can figure out where to find the settings I'm sure it could be optimized a lot(My first day of linux). Seems like if I dont run anything else it may be okay? So I suppose keeping the encoder resolution down to only what I need may help if I run into problems?

As for the target machine its a former Moog Hydrapoint. After removing all the hydraulic parts its now basically a type 1 bridgeport with a heavy duty box-way knee and heavy duty/wide saddle. The head and ram are typical bridgeport v-ram and 2J varispeed head.
My plan is to assign the knee as the "W" axis and move it mostly for work/tool offsets. The quill will be the "Z". (I'm in the early stages of mounting the ballscrews right now.) I also fully intend to run a 4th axis(A) as soon as I have the 3 axis(including the knee) all ironed out. As stated in the first post I will be using a VFD and plan to add an encoder for rigid tapping. Oh, this will not be a stepper system, but a servo setup using my own H-bridges that only need a pwm signal and dir signal for input.

I have been looking at the Mesa 5i25+7i76 combo, and am wondering if this pci based solution is as sensitive to latency issues as a parallel port? I know you can push a lot of data through a pci for video cards, which seems like a lot more than a cnc would use.But of course I dont know how well the pci bus is exploited by EMC or Mesa?

As to the encoders I see that the 7i76 only has encoder inputs for the spindle, so I guess I'll have to bring the encoder signals in through the other DB25 socket on the 5i25? Now if a hook up another 7i76 to it(the 5i25) could I perhaps use some of the servo ports if ever needed and re-configure the others as encoder inputs?

anyhow thanks, and it looks like I have a ton more reading to do!
Marvin

[samco]

Cool - 25us is actually not too bad for a software stepping solution...

That being said - external interface hardware like mesa - you do not need as good latency. IMHO you would still want <50us though. The hardware does the heavy lifting like stepgen/pwmgen/encoder counting. So linuxcnc only needs the 1ms servo thread.

Can I ask why you are getting a stepper daughter card? It thought you where going to go analogue?

Peter form mesa might chime in here. I don't know the specifics of the 5i25 (I have used the 5i20) I know he builds custom firmware for people that want to do different things with the 5i25.

sam

[PCW_MESA]

Thanks for the response, and I have enjoyed reading about that K&T Conversion, these things inspire me.

Ok, I have made a little progress in the understanding of this, but now have some new questions.
First though, I have resurrected one of my old computers for testing. Its a celeron e1200 dual core which currently runs at 1.9Ghz. The mobo is an asus P5Q pro which I still like due to the all solid state caps and such (I have a stack of old motherboards with puffed up electrolytic caps). It has a basic Nvidia 8500GT card with dual head output. Memory is 2Gb ram (forgot the speed). And an old WD 250gb hdd.

Anyhow, after a fresh install from the live CD I was immediately pleased to see that the pair of LCD's I have attached both work properly spanning the desktop across both screens! I am not running the proprietary nvidia drivers, just the default that was loaded (I havent figured out how to find the driver info yet).

So running the latency test I get about 4500-5000 (stable for hours) on the 1ms test when idle. Loading glxgears and then other apps causes spikes up into the 25,000 range, while settleing down for several seconds in the 6000-8000 range and then spiking up again occasionally. If I can figure out where to find the settings I'm sure it could be optimized a lot(My first day of linux). Seems like if I dont run anything else it may be okay? So I suppose keeping the encoder resolution down to only what I need may help if I run into problems?

As for the target machine its a former Moog Hydrapoint. After removing all the hydraulic parts its now basically a type 1 bridgeport with a heavy duty box-way knee and heavy duty/wide saddle. The head and ram are typical bridgeport v-ram and 2J varispeed head.
My plan is to assign the knee as the "W" axis and move it mostly for work/tool offsets. The quill will be the "Z". (I'm in the early stages of mounting the ballscrews right now.) I also fully intend to run a 4th axis(A) as soon as I have the 3 axis(including the knee) all ironed out. As stated in the first post I will be using a VFD and plan to add an encoder for rigid tapping. Oh, this will not be a stepper system, but a servo setup using my own H-bridges that only need a pwm signal and dir signal for input.

I have been looking at the Mesa 5i25+7i76 combo, and am wondering if this pci based solution is as sensitive to latency issues as a parallel port? I know you can push a lot of data through a pci for video cards, which seems like a lot more than a cnc would use.But of course I dont know how well the pci bus is exploited by EMC or Mesa?

As to the encoders I see that the 7i76 only has encoder inputs for the spindle, so I guess I'll have to bring the encoder signals in through the other DB25 socket on the 5i25? Now if a hook up another 7i76 to it(the 5i25) could I perhaps use some of the servo ports if ever needed and re-configure the others as encoder inputs?

anyhow thanks, and it looks like I have a ton more reading to do!
Marvin

If you want encoder inputs and PWM outputs. There are a couple of ways we can do this:
one is the new 7I85S daughtercard for the 5I25 (4 encoder inputs and 5 step/dir or PWM/dir outputs). The 50 pin interface FPGA cards can also do this with a 5I20/5I23 FPGA card and a 7I52S daughtercard (6 encoder inputs and 6 step/dir or PWM/dir outputs)

You can also just use the bare FPGA outputs on the 5I25 but you need you protect them
from voltages in excess of 7V on inputs and drawing more tha 24 mA on outputs

[punisher454]

Can I ask why you are getting a stepper daughter card? It thought you where going to go analogue?

By analog I assume you mean something like a +-10v signal to a traditional servo amp. I plan to roll my own h-bridge setup and would like to just use a pwm signal to the gate driver chips, along with a dir signal to select the direction of the h-bridge.
I'm already accustomed to doing it this way on the brushless motor controllers I've made with AVR uc's. My thinking has been that its simpler than generating an analog voltage, then just converting it back to a pwm at the gate driver.
Of course if it would make the interface simpler on the PC side of things I could very easily add a uC to the boards to do an analog interface plus some current and temperature monitoring functions as well.

As for the Mesa card, the 5i20(23) looks like a better way to go than the 5i25. The final cost isnt really that much more but it looks like it leaves a lot more room to grow.

thanks for all the help so far.
Marvin

[samco]

I started doing that... Building my own pwm amps... I got to a working prototype after about 6 revisions.. (but I needed 20ish amps at 200v - not trivial)

http://www.cnczone.com/forums/linuxc...tup_cheap.html

I ended up keeping track of ebay and at that point found some 40A 400v amc analog drives. Cheap. So I went that route...

Yes - I think the 5i20 style cards are probably a bit more flexible (just my thinking) (use the raw pwm from the card and count ttl encoders. (or build differential transivers..) I would still probably buy atleast the 7i33 or 7i48 to get the differential recivers for the encoders. You could hack the pwm out of the ribbon cable instead of using the +/-10v. (or use another 50 pin plug for it)

just thinking out loud.

sam

[punisher454]

You could hack the pwm out of the ribbon cable instead of using the +/-10v. (or use another 50 pin plug for it)

Oh I like the sound of that. So does the 5i20 send both a pwm and a dir signal to the daughter card which then converts that to +-10v? If so that sounds real easy to deal with.

As for multiple revisions on drivers, I got real good at letting the smoke out of fet's on my last project :\ So I built a PCB printer(fun project) and started making modular dev boards and it accelerated the process a lot and allowed me to recycle more components. I'll probably use the same process this time.

Your giving me all kinds of new ideas.

[samco]

something like that.. The hostmot driver is very flexable... you can do pretty much whatever you want...

HOSTMOT2

sam

Oh I like the sound of that. So does the 5i20 send both a pwm and a dir signal to the daughter card which then converts that to +-10v? If so that sounds real easy to deal with.

As for multiple revisions on drivers, I got real good at letting the smoke out of fet's on my last project :\ So I built a PCB printer(fun project) and started making modular dev boards and it accelerated the process a lot and allowed me to recycle more components. I'll probably use the same process this time.

Your giving me all kinds of new ideas.

[scrambled]

Punisher454

I am in the same boat. I am in the process of rebuilding my moog hydrapath b22. I am still trying to figure out the best way to go. So far I have removed all of the electronics. I will be watching what you do, so keep us posted


Steve

[punisher454]

I think the b22 is a lot newer than what I have. this one was all hydraulic as far as I can tell. The lines had been cut from the machine, and I believe the ram and head may not have been original, since they are standard bridgeport type. In fact on this machine now all that is different than a standard bridgeport manual knee mill is the knee, saddle and table, all of which are a lot heavier.
I am currently in the process of building end plates for the saddle and knee which by the looks of things is going to be a lot easier than a regular BP Last week I made a custom 120tooth 5mmHTD pulley (about 7" dia) for the knee drive which will occupy the space where the bevel gear used to sit. I have a real nice 1.25"dia ballscrew from a Mazak that will replace the acme elevating screw. I'll be mounting the kneedrive motor inside the knee and still have room to spare for the Y screw. The knee and saddle have a lot of open space to do just about anything you want inside. I also just scored a pair of ballscrews from an Anilam for the X&Y that are just the right length from a friend for a hundred bucks Looks like the only screw I'll have to do any lathe work on is the Z screw for the quill drive.
I'll start a build thread sometime in July when I get a bunch of the parts I'm waiting on. I looked for quite a while for a Regular BP mill to convert, but could never find one for a decent price in my area. A guy at school had this sitting in his garage for fifteen years and was tired of looking at it. Apparently people avoid the Moog's like the plague, but it seems to me that once you get it all stripped down to the basic iron its a nice sturdy machine. I wouldnt hesitate for a minute to pick up another one after this.