How to select Driver Boards?? - Design Considerations?

I was going to use the Parallel port to run my steppers, but after reading a lot of threads with divergent opinions I think I should abandon this design view.

I would like to get a current "October 2018", and state of the art, view of the hardware landscape.before I waste anymore cash.

I was on the following path with Steppers ...

• Select motor

1. Determine torque requirement (this is the primary engineering requirement)
2. Assess desired speed (torque/speed curve from mfg, the one I used is attached. I am not sure this is fast enough.
   
3. Determine constraints Voltage/Current
4. Select Motor that will meet above while working with controller below. (This is an optimization there is no perfect answer)

Select Stepper Control board

1. Determine Control board type (I chose dir/pul type, This might be a bad decision manual attached)
   
2. Match Current and Voltage specs for motor
3. Optimize ... the motor & controller for cost

Select Computer Interface board(s) (This is where I got stuck and started searching.)

1. Match Board to the stepper control type
2. Determine additional requirements
   1. Connection DB25 or Ethernet
   2. Number of axis
   3. Number of I/O ports
   4. Other features

(I thought I had settled on a 7i76E or 7i96, but have no idea on how to decide. Help would still be greatly appreciated,)

But .. THEN....I realized ... I might be on the wrong track all together..
It seems from reading many threads while researching the MESA cards. That the developers have moved away from steppers completely.

It makes sense to me that going forward I should follow their lead. There is, after-all, an incentive to maintain this gear. Would someone please stipulate what they are using? Perhaps we can follow suit?

For example:

What class / type of motor? I assume servos, but what are the key things to look for in making a purchase?
I assume there are some important specifications, beyond just power (Voltage and Current). Please, what are they?

Assuming it makes sense to go with servos ( I am constrained to a NEMA 23 form factor). What is needed upstream from the motor?. For example, is there an equivalent to the stepper control driver? A couple of end to end examples would be great!

Can I maximize flexibility and choose something that can evolve with my needs?

I have looked at the MESA boards and I am aware of FPGA technology (past life). But no idea where I should go next since firmware is a critical element in FPGA functionality and I dunno what to look for :blink: :blink: .

I think a huge part of this is just getting some solid examples to inspire from and maybe a sticky for future folks embarking on this journey. A here is what you will need road-map.

I will volunteer to write a sticky if I can get the knowledge to get the contents correct.

Good morning irakandjii

I have a lot of things to learn, for now I have used stepper motors driven step dir I would summarize as follows:

-Open circuit step by step drives, no one knows if they lose steps.
-The maximum number of laps in relation to the pair is very low.
-However, if you choose step motor correctly and you are satisfied with the low speed, they work well.
-Inserting an encoder into the stepper motor only serves to detect error made and stop the machine.

Linuxcnc, when using the parallel port the speed (frequency of the steps) is limited, and therefore considering using microstepping it becomes complicated (complicated because it will have to work very slowly).

Now I'm doing a retrofit to a machining center 3 axes x axis A spindle with encoder and tool change, my choice was this:

-I chose to drive the drivers step dir because there are many CNC controls that use this mode of piloting , my main choice will be
linuxcnc but as I'm not prepared to configure HAL (however I'll try to learn)) if I should not be able to choose another CNC.
-I have to drive 3 old Fanuc AC motors with incremental encoder, I bought 3 ARGON drivers and they work great.
-The spindle is always a Fanuc AC and I drive it with a SIEMENS sinamics V20 inverter
-For the time being, axis A is in standby
-The tool change will move autonomously controlled, I will only need to change the tool, and the tool from linuxcnc, when the tool
change is done, I will communicate it to linuxcnc that should resume working. (I think this can be done with linuxcnc but now I'm not
capable.)
-To generate the step-by-step signals, the home signals, the spindle with encoder, and to drive the tool change, I chose MESA 6i25 +
7i76.

Saluti Giampiero

NB for the moment I talked about my choice then I will have to ask many things about the configuration of linuxcnc

LinuxCNC fully supports both steppers and servos. (including step-controlled servos and closed-loop steppers).

There is no reason to use servos if your machine isn't of a size, weight, or speed to require them.

Also, the choice is not just DB25 or Ethernet, there are also PCI and SPI options.

Thanks Andy. It is nice to hear the stuff is supported BUT...
Are there any specifics documented anywhere? I have searched the documentation and the forums, but cannot find documentation other than for XP class machines.

What do you use for example?

The documentation I provided is for a closed loop stepper set-up looks like a reasonable compromise. But to use this I need to select a MESA card. I was considering a 7i96 or 7i96e but based on this forum it is unclear how well it is supported.

I also saw references to LinuxCNC 2.8 for MESA cards, yet I cannot find 2.8 when I go to the downloads page. I must be missing something.

BTW
I use SPI in my micro controller work, I would never specify it for something like this.
PCI is outdated and generally deprecated so I would not use that

irakandjii wrote: Thanks Andy. It is nice to hear the stuff is supported BUT...
Are there any specifics documented anywhere? I have searched the documentation and the forums, but cannot find documentation other than for XP class machines.

I am not really sure what question you are asking here ?

What do you use for example?

My last build (a couple of years ago) uses a couple of 1kW servo motors I found cheap, with resolver feedback, controlled by Mesa 8i20 drives connected to a 7i49 resolver card and a 7i84 for GPIO and a 7i24 PCI card for the FPGA.
But the Mesa cards alone cost more than my entire first CNC machine, at that included a new lathe/mill !

The documentation I provided is for a closed loop stepper set-up looks like a reasonable compromise.

Closed-loop steppers are basically a high pole-count brushless motor, they can work very well.

But to use this I need to select a MESA card. I was considering a 7i96 or 7i96e but based on this forum it is unclear how well it is supported
I also saw references to LinuxCNC 2.8 for MESA cards, yet I cannot find 2.8 when I go to the downloads page. I must be missing something.

"2.8" is shorthand for "the current "master" development version". It is available from buildbot.linuxcnc.org but it is in a constant state of flux...

I use SPI in my micro controller work, I would never specify it for something like this.

But it is the only real option with a Raspberry Pi.

PCI is outdated and generally deprecated so I would not use that

What would you use instead? I don't see any direct replacement.

Thanks Andy

The first part was a request for a link to where I can find design information. I want to learn and make some purchase decisions. I have invested over 1k so far and I know I have more yet to spend. I just don't want to make any more mistakes.

On PCI we might be talking about the same thing. When I reference DB25 I was talking about a MESA PCIe card with a DB25 connecting to a daughter card. I realized afterwards I was a bit vague.

I am decision neutral on the Ethernet vs PCIe / DB25 approach. Though a LAN based connection has some advantages in the placement of the CPU. So if all else is equal that is the way I would go.

Ah ok on the 2.8 build, I am using the GIT master for source. Is this buildbot master build the same or different?
I used the instructions on the site to get the release from GIT, so now I am confused regarding the official release site.

These buildbot files seem to only support precise. Am I reading that wrong? Or will it run on a stable preempt kernel?
I need to use Bionic and have compiled the most recent Preempt-RT kernel. Which runs without error and passes the LinuxCNC test suite.

BTW .. I would not use a raspi as a front end so it never occurred to me, I use a lot of them, but never for mission critical stuff. I might have used an Edison, but they are now deprecated. (sigh remembers all those now wasted hours with the real time core on that puppy)