[MrMetric]

I couldn't find the "perfect" place for this question, but given that I'm using a Granite Devices driver and it has the (way cool) option of either supporting step/direction or analog interfacing to a servo, maybe the question belongs here!

I have a few fairly simple questions... I am converting an old Hurco mill's control. I have settled on EMC because Mach seems to have so many nay-sayers out there and being familiar with Linux, I don't have that technical hurdle. The mill will keep the old servos because they are fine but I am changing the amps to Granite Devices VSD-E drivers. Those units can be configured to accept either step/direction or analog inputs. I will be using a Mesa board for integration to the PC but I am trying to identify *which* board to get. So, here are the questions:

1. I can either integrate with step/direction or analog. Because the Mesa card can act as a pulse generator, I am guessing that the step generation rate should be reasonable. However, I wanted to solicit input on *which* way to go. This will drive, of course, which Mesa breakout board I ultimately buy

2. If I go down the analog route, I gather I will need to feed the encoder signals back to the control (through the Mesa board). However, I've seen that some people feed the encoders back to the control even if they have a step/direction setup (i.e. running closed loop). I thought I would solicit thoughts on whether or not this is beneficial, given that the driver itself is monitoring the encoder lines; as such, the driver should be able to determine if there is an error due to a fault, crash, etc.

3. which Mesa board is the best "bang for the buck" for the creation of a CNC mill? I have some thoughts but I figured I'd find out if people out there have favorites.

4. I know the ethernet based "smooth stepper" is a no-go with EMC; however, are there other interface systems out there that are supported by EMC and that use ethernet? For some odd reason I seem to like this idea. I think this is due to the fact that I can mount the motherboard directly into my electrical box and not have to have any boards plugged in that need to be supported (physically). Ethernet cables also have a very nice physical lock but can still be removed/moved easily. Perhaps this is an unreasonable consideration so people can feel free to comment on this too. :-)

[Al_The_Man]

I primarily use motion cards and my personal preference is to use analogue drives in the torque mode, such as A-M-C, there is no loop back to the drive, apart from the commutation pulses if using BLDC.
This is one advantage to using a card where the PID loop is closed back to the controller, you do not need 'Intelligent' drives.
Al.

[MrMetric]

Thank you for the response, Albert.

I should have added something in my original post. The servos are not BLDC, they are ElectroCraft brushed DC servos. As for the drive intelligence, I have already decided to use the Granite VSD-E drives. I have some AMC drives too that I could use, I suppose, but I like opted to go down the Granite route because, in part, I liked the digital tuning that is available with them. I had such a difficult time keeping my (albeit ancient) Servo Dynamics drives in tune that I wanted to try something new.

Alan

[Al_The_Man]

You can also run brushed motors on A-M-C BLDC drives, they take either.
You don't have to tune the drives, just the motion card PID loop.
Al.

[MrMetric]

Just out of curiosity, which AMC series are you referring to?

[Al_The_Man]

Varies, B30A8, through B40A20 to B100A40 etc.
Al.

[MrMetric]

Herein lies the problem. Those drives look attractive but the price point puts them outside the realm of my (hobby) checkbook. The Granite Devices have a lot more bang for the buck. Neither Gecko nor Granite are competing directly against AMC, as far as I can tell.

[Al_The_Man]

That's why they are on my Ebay watch list!
One Example: A while ago I picked up a box of 10 NOS Copley Controls BLDC, (essentially a similar drive) for under a grand.
Same for Servo motors.
Al.

[samco]

I like for $239 you can get an industrial quality 6 axis(6 analog and 6 encoder counters (ttl/diff)) 48i/o plus it is expandable.. (pci mesa 5i25 + 7I77)

I have used mesa hardware (5i20) and love it. no - really - Love it!

sam

[MrMetric]

Thank you for your response... It seems like analog is the preferred method to interface. This really was the main question I was trying to answer and the conclusion is based on feedback here and in the CAD_CAM_DRO yahoo group. Determining this, I can select the appropriate interface board. In the CAD_CAM_DRO group it was also suggested that I look at Jon Elson's boards in addition to Mesa.

I am actually have a problem with my older VSD-E (80VDC) unit now and I'm curious if anyone else has had this. When I try to update the firmware, I get a failure while updating and I'm not sure if the issue is with the drive or the USB adapter. The latter is correctly recognized when starting the flasher application. Here are the steps:

1. connect 12VDC. alternating red/blue, 1 sec each (previously flashed both quickly)
2. Start 'flasher'
3. app sees USB and gives message about cycling power on drive
4. Turn Off, then ON 12VDC
5. Unit's green LED solid, red is flashing.
6. Open DualDrive firmware file
7. Start download.
8. GDFlasher shows Flashing 1/189, very briefly red LED blinks like it is getting data. Green LED remains lit
9. Get an error indicating "Flashing failed, drive in unexpected state....." Green LED is lit, Red and Blue blink together at about 1 second interval.
10. Cycle power and now Green is not lit, red and blue alternate (#1).

Has anyone experienced this type of behavior? If so, how did you get the firmware loaded. I'd hate to have a bricked drive.

[Xerxes]

Thank you for your response... It seems like analog is the preferred method to interface. This really was the main question I was trying to answer and the conclusion is based on feedback here and in the CAD_CAM_DRO yahoo group. Determining this, I can select the appropriate interface board. In the CAD_CAM_DRO group it was also suggested that I look at Jon Elson's boards in addition to Mesa.

I am actually have a problem with my older VSD-E (80VDC) unit now and I'm curious if anyone else has had this. When I try to update the firmware, I get a failure while updating and I'm not sure if the issue is with the drive or the USB adapter. The latter is correctly recognized when starting the flasher application. Here are the steps:

1. connect 12VDC. alternating red/blue, 1 sec each (previously flashed both quickly)
2. Start 'flasher'
3. app sees USB and gives message about cycling power on drive
4. Turn Off, then ON 12VDC
5. Unit's green LED solid, red is flashing.
6. Open DualDrive firmware file
7. Start download.
8. GDFlasher shows Flashing 1/189, very briefly red LED blinks like it is getting data. Green LED remains lit
9. Get an error indicating "Flashing failed, drive in unexpected state....." Green LED is lit, Red and Blue blink together at about 1 second interval.
10. Cycle power and now Green is not lit, red and blue alternate (#1).

Has anyone experienced this type of behavior? If so, how did you get the firmware loaded. I'd hate to have a bricked drive.

80VDC VSD-E does'n support DualDC mode. You can restore drive's original firmware with GDflasher by loading VSDE-VSDXE-80-Singleaxis-V204.gdf firmware to it.

Also, when choosing between input methods, please remember that DualDC supports only step/dir. The single axis mode supports step/dir, analog, quadrature and pwm. Many use Mesa cards with step/dir or quadrature mode with success so I can recommend that. There's nothing wrong with analog but may sometimes cause troubles as it's not galvanically isolated like digital inputs of drive.

[MrMetric]

Hi,
Darn, I meant to fix that mistake in the posting (cut 'n paste error). However, I think I have identified the error in my ways. I went from using one incorrect file to another. I originally thought I was flashing the 160VDC version and hence attempted to upload the 160V firmware. When I discovered that my unit was an 80VDC, I went the other way and am now attempting to flash the VSD-A version. Duh! Yes, I feel foolish. I'll try to flash the correct version tonight. Thank you for straightening me out.

Regarding the DualDrive's inability to work in analog... Yes, I had forgotten about that tidbit of information on the 160VDC version. Shoot. I was all set to go down the path of using analog. <sigh> That said, one of the great things about your drives is that I can start with step/direction to keep my costs down and then migrate to analog later. The only "loss"will be the replacement of the Mesa breakout board and that seems acceptable. I love the built-in ability to upgrade the boards to a different control paradigm.

This is a great chance to query you for your thoughts about step/direction versus analog too, however. My guess is that you will follow the two other respondents and say analog is better, but perhaps not. I am very curious.

Alan

[MrMetric]

I've confirmed that I'm humbled and feeling not just a little stupid right now. Do you ever have that "The answer was staring me right in the face but I was too blind to see it" feeling? Well, that is what I have. Once I selected the *correct* firmware, I unbricked my VSD-E80VDC unit. Whew.

I have to decide what to do. I'm strongly leaning towards using analog mode integration. It 'feels' right and seems to have a consensus as to being the best way to go. Unfortunately it doubles the cost because I can't use the DualDC feature. This makes it a tough sell so I have to give it some serious thought. I've got some AMC amps sitting around. Although they are not as nice as the ones Al was pointing to, maybe it makes sense to use them for the time being