New plasmac build

Currently building my plasma table. Checking out controls and i have Linuxcnc running my router table, it has worked flawlessly for years. So i kinda like the Linuxcnc platform now, other then i did mine way back when gantry machines was not really supported and i lost a few hairs getting it working. Just seen LinuxCNC now has plasmac. Have a question on the Mesa card as i dont currently use one on my router. Does the Mesa take the place of a BOB? Or do i need a BOB plus a Mesa? Also which is the preferred card 7i76e or 7i96? Oh one more thing if i run Mesa cards i dont have to be worried as much about my pc's latency right as the Mesa smooths all that out if i remember right?

Hi.
Gantry was akways supported. Check at web whats gantry mean.
If you go the 7I76 route so this use ethernet and this is will be your BOB (inferface between your computer and you machinery).
7I76e or 7I76 is all about input type, 7I76e use PNP.
NPN is common used from machinary from japan.
Some people argue PNP in industry is more easy for troubleshoot.
Here usualky people use PNP (me too)I read somewhere here at forum PNP is the way to go if you wanna use plasma...PCW and Rod was talking i think...
Latency doesn’t matter too much using mesa, check your ethernet i think matter if you use 7I76, someone can explain better if im telling bullshit.
Try ti use google like that:
site:forum.linuxcnc.org plasma pnp
Enjoy your assembly

Yes, the mesa cards (eg 7i96, 7i76e) can replace the BOB.
V 2.8 of linuxcnc introduced the joint axes which solves the control and alignment of gantry machines with two motors.

The mesa cards generate steps in hardware so the need to run the base thread is removed. So therefore demands for latency is less.

Most people use a Mesa ethernet card (7i76e or 7i96) for plasma macjines to gain more galvanic isolation between the plasma environment and the PC for noise control.

The 7i96 is a good choice for plasma but lacks MPG inputs. You can convert inputs to MPG inputs but there are not many inputs to start with. The 7i96 has relays built in to the outputs, the 7i76e does not.

The Mesa THCAD is used to read the torch voltage and plasmac manages the THC side of things.

A second THCAD can be used for ohmic sensing in conjunction with a component I wrote. Its not in mainstream yet. There is additional firmware from mesa that supports 3 THCADS on a mesa card. Using a THCAD for Ohmic senisng releases a couple of inputs which is a good idea on the 7i96 where they are limited in number to start with.

Coming from a BoB with 5 inputs, the 11 inputs on the 7i96 feels like luxury!

Thanks for the info rodw. Whats the advantage of the 7i96 over the 7i76e? Other then the price of course. Is one "easier" to configure then the other, i am all for easy lol

Wow i need pay attention.
How many inputs you need?
Do you plan to use MPG?
how many limit and home switches you need?
Need physical buttons or no (run, stop, pause etc)
Builtin relay save money but im prefer no builtin.
You need write down to find whats better for you.

Hippy wrote: Thanks for the info rodw. Whats the advantage of the 7i96 over the 7i76e? Other then the price of course. Is one "easier" to configure then the other, i am all for easy lol

In many ways the 7i96 is perfect for plasma cutting. With built in relays and no spindle control, the ability to work with both active low and active high hardware and adequate I/O particularly if hypersensing is used.

There will be no difference in ease of use.

For reference I just got my plasma running with what I think is the absolute bare minimum of IO. I'm using a 7i96 with 1 input for a torch float switch, 1 for ArcOK, and one more for estop. And I have room for my 5 homing switches I plan to install later.

I actually first purchased the 7i76 until I realized it was overkill for my particular machine and swapped it out for the 7i96.

Decided to go with the 7i96 and the plan was to go with THCAD5's but it appears the Mesa store is out of stock and only have THCAD10's. Might be a stupid question but what is the difference between the two?

Hippy wrote: Decided to go with the 7i96 and the plan was to go with THCAD5's but it appears the Mesa store is out of stock and only have THCAD10's. Might be a stupid question but what is the difference between the two?

the amount of voltage they can read. 5 is 0-5v, 10 is 0-10v, 300 is 0-300v.

You want to size them based on your particular needs. For example, I have a Hypertherm 65, and I determined that the max cutting voltage listed in the charts was around 150v. At 20:1 divider, that voltage would give me 7.5v, so I chose a THCAD 10. 200v would be the max it could read, but they can handle something like 500v for an indefinite amount of time.

That said, the Hypertherm default is 50:1, so if you didnt want to take the machine apart to cahnge it, you would run a THCAD 5.

Basically I wanted the highest fidelity, which was the lowest diviser with the lowest card that would read it.

Hopefully that makes sense?

Lastly, if you didnt want to wait, but wanted a THCAD 5, you could swap the resistors on the board for a different value to change the card to the other model. PCW commented on the resistance values to do so a few times, you'll have to search, or wait for him to chime in.