Which Mesa combination should I choose?

I have a simple gantry router similar to the Openbuilds LEAD machine. Linuxcnc drives the steppers through a CNC4pc C50R1 bob which also has the E-stop and probe connections. The prox and limit switches are connected through a C10 bob. All axes are driven by lead screws at 2540 pulses per inch. The maximum frequency for any axis is about 8800Hz. Currently there are 9 inputs and 1 output not counting the steppers. I will probably add another output to control the router at some point. The router speed is controlled by an ESP8266 inspired by the Super-PID connected to a KBIC125.

Linuxcnc currently runs on a Gigabyte GA-E350N-WIN but I just got a HP 8300 with an i5-3570 as a replacement. Both PCs have a realtime latency of about 20us or less. While I haven't tested the Preempt latency for a long period the 8300 was less than 100us. Given the apparent direction of the Linuxcnc software it seems like this might be an opportune time to move away from the parallel port connection. This PC gets as much use as a general purpose PC in my garage as it does running Linuxcnc and Wheezy is a problem for some other software. The desire to move away from the parallel port is driven by software direction rather than a performance improvement. Any improvement in machine performance would certainly be welcome but not expected.

With so many options in the Mesa line I am a little confused as to the “best” choice. I have read through a bunch of other posts but none gave me the confidence to place an order. It seems the 7i76e/7i96e are currently very popular and either would accommodate current and future I/O needs. The 7i92 seems like it might be easier if it can connect to my existing bobs. However, any future expansion might be more difficult. I haven’t really explored other options within the Mesa line.

All suggestions are welcome.

John

I'm far from a pro, but i'll go with the 7i96, and it has expansion ports
Esay to setup, lots of in/out ports, a couple of encoder inputs a well

It seems the 7i76e/7i96e are currently very popular and either would accommodate current and future I/O needs. The 7i92 seems like it might be easier if it can connect to my existing bobs. However,

The 7i96 or 7i92 does not have the spindle control 0-10V or spindle encoder like the 7i76e but if you don't need that then the 7i96 is a nice choice

I think with a spindle if you have the budget, just go to the 7i76e (or 5i25/5i26 plus 7i76). 32 inputs and 16 outputs plus heaps of extras.

The ethernet cards require PREEMPT_RT kernal.

All of them & quickly, time is running out for "He who dies with the most toys wins"

7i92 & 7i76. or 7i76e.

Some of the reasoning I went with Ethernet.
1. Easier to swap out a failing computer, even if the MB is in the control cabinet a backup can be patched in by just swapping an Ethernet cable.
2. Who knows when PCIe ports are going to be dropped from consumer pcs and reasonably priced MBs, what I call futrue proof insurance.
3. A good range of SBCs can be used, some of the better ones have a non-usb Ethernet connection.
4. If for whatever reason you have your PC further away from the main controller connection is easier with an Ethernet cable.
5. RTAI & The Evil That Is UEFI, don't play nicely at the moment. RT_PREEMPT can be used with UEFI firmwares.....I don't want to refer to it as a BIOS.

These are just my opinions, apart from UEFI being evil, that is gospel

Looks like the 7i76 is the preferred choice for future expansion. The 7i96 would cover my current needs. If I look back at the evolution of my machine over the years it is clear future change is inevitable!

I found Norbert's connection guide which will be a great help. Thanks for all the current and likely future help.

John

cncbeagle wrote:

Looks like the 7i76 is the preferred choice for future expansion. The 7i96 would cover my current needs. If I look back at the evolution of my machine over the years it is clear future change is inevitable!

I found Norbert's connection guide which will be a great help. Thanks for all the current and likely future help.

John

Sounds like a good choice. I think I have used just about all of the 7i76e's 32 inputs! And most of the outputs!

One mistake I did was to use the analog inputs early in the piece for digital inputs. Nrbert sets it straight but he released that after I wired everything up so I have never gone back to it.

Following up on the original question.

I did purchase a 7i76e and now have it hooked up and operating. I now have spindle start/stop and speed control. My spindle is a Porter Cable router fed through a KBIC-125 speed controller.

There may still be some optimization opportunities. In testing the gantry steppers before mechanically connecting them I noticed one was limited to a lower speed than the others. I have ordered two new higher torque, lower impedance steppers. The gantry speed has been what limits my cutting speed. I'll see if the more powerful motors help or if one of the Longs Motors DM542A drivers is the culprit.

I am able to drive my X axis much faster with the Mesa board than with the parallel port. It has a larger motor and DM556 driver. I have tested it up to about 15KHz but limit it to about 10KHz in operation as that is still faster than the Y gantry. With the parallel port it operated at about 8KHz. It might have been able to go a little faster but never at 15KHz.

The change to Mesa was driven by a PC software and hardware upgrade. Any performance gain is a bonus. I was able to simplify some wiring and now my CNC machine is all on a single table that I can move around my shop as needed. The PC gets as much use as a general purpose computer as it does running LinuxCNC.

For me this has been a worthwhile upgrade. Thanks to many on this forum it was relatively easy if a bit time consuming.

Another follow up in case someone finds this thread useful...

I finally received the new stepper motors for my Y gantry. The new motors are higher torque and lower inductance. With these motors I have more than doubled the speed of my Y axis. I am hesitant to push even further but probably could. I suspect these speeds would have been beyond the reliable limit of my former parallel port setup.

Just another reason to be satisfied with the Mesa upgrade.

Also I'm looking at connecting outputs to control an air "blast" and vacuum. Having all this unused I/O is giving me lots of ideas!