Best Ethernet Based Board in 2020

Hello,

I have been researching for quite some time about CNC stuff and have decided to build my own cnc plasma table. What I dont quite understand is the part where the computer interfaces with the smooth stepper/main board.

I would really like to use teknic servos (closed loop of course) but I havent really found any good examples on how to do this with linuxcnc.

What is the best proven Ethernet based board that is compatible with linuxcnc.

Thanks in advance for any help you can give!

welcome to the dark side.. Ooops the wonderful world of linuxcnc!

Smoothsteppers are not compatible. They are a motion controller in their own right. Here the motion is always controlled in the PC by Linuxcnc. We think that has advantages.... like it has the full power of a PC CPU at its disposal instead of a small microprocessor on an external board.

With Linuxcnc, the configuration is controlled by an .ini fle that describes the fixed hardware portion and a hal file which describes how that hardware is used (wired together if you will). These are both text file sand there are tools called stepconf and pncconf that will create these for you from a GUI interface.

The ethernet cards used typically are from Mesa and must live on a dedicated ethernet NIC on the PC. Typically the card is configured with an ip address of 10.10.10.10 and the PC is configured as having a fixed IP of 10.10.10.1. Once configured, you should be able to ping it from the PC as normal.

The hal file loads a driver which connects to the mesa card and any connected daughter cards. The pins are then published in
HAL (the hardware abstraction layer). After that, the mesa card is treated just like it was any other piece of hardware (such as a parallel port breakout board). Within HAL, linuxcnc also publishes its own pins that control the system. eg a signal to turn a spindle motor on or a pin to receive the home switch input for a particular joint (motor).

Within the hal file, we do the logical wiring to connect things to interface with the real world. So we might connect the spindle on signal to a specific output pin which is connected to a relay to power the spindle (or turn a plasma torch on)

If you are going to use clearpath, you just use their drivers and the encoder feedback is closed there so it looks like any other step and direction interface from Linuxcnc.

With that in mind, there are two Mesa Ethernet options:
the 7i96 which is a good choice for plasma as it has relays built into it but its a bit limited in the number of I/O pins (it just has enough for plasma.)

the more expensive 7i76e has no constraints with IO pins (32 inputs, 16 outputs) but requires external relays. Additionally it has two MPG jog wheel inputs. You can add MPG's to the 7i96 but it is at the expense of input pins so its not really doable.

Both board can have 5 stepgens so can control 5 motors each.

So in summary, get the 7i96 on a budget but if you want to add MPG jog wheels or are an experimenter type who wants to fiddles with his config, the 7i76e is a better option.

Hello and thank you for the replies.

I am a c++ linux developer so naturally I lean towards linux whenever possible. LinuxCNC seems better, faster and proven. The electronics side of this I am not great at all though I do know how to use a fluke volt meter


Within reason I am not really on a budget, I just want to build a quality table

mesa store sells
"7I76ED STEP/IO Step & dir plus I/O daughtercard - sinking output version"
"7I76E STEP/IO Step & dir plus I/O daughtercard - sourcing output version" <-- this one?

Which one do I buy?


So if I have this right it should go something like this
1. Computer with LinuxCNC iso loaded
2. Shielded Ethernet (maybe cat7? because of the better shielding) from the pc to the 7I76E board (does this need to be a crossover cable)?
3. Some kind of driver board that can supply the amperage for the servos. EDIT: I meant to act as a 'relay' to control the output of the power supply to the motor
4. Clearpath teknic servos (should I be looking at a different brand for closed loop?)


LinuxCNC -> 7I76E -> Servo Driver Board(s) -> Servos


Also my gantry will have two servos to move the X access so I think i will need at least a 4 axis system (7176 looks like it has 5 I just hope it can 'mirror' two of the outputs)

The 7I76E card doesnt have anything to do with the 'closed loop/servo' right?
Meaning if a 'step' is missed the 7I76E wont even know about it? The catch-up of the missed steps will be handled between the driver card and the servo?

The 7i76e is the one to get for a new build. The D version is active low so its useful for retrofits with that style of wiring.
Straight through ethernet cable is all you need.
Once you get into it, be sure to read up on halcompile. That lets you write a few lines of C whenever you want to do that the standard components can't do or becomes convoluted requiring several standard components, you can write your own components. which are compiled and installed with one line at the command prompt.

if you got a system running just get you a 7i92 and within minutes you are up again on the ETH
if you start over it is as the treads above but consider the mashine needs to the board

Hi
For the ethernet shilding.
Be carefull with shielded cable. If you do not have a very low impedance ground connection you will have those emv currents running between your pc and the 7i76e running over the tiny ethernet shielding wires.
And none of both sides is made for low impedance connection to ground, capable of highe currents.
So better use unshielded and plan a good ground conection with adequate cabling between pc and machine. And no, just the earthing of your current supplies is not enough.
m5c
Mike