Which Mesa board?

palmac wrote: Rod, yes I'll order the board soon. One last question, if I go with the 7i92 is a wired MPG going to give me much grief to set up?

Probably but I'm not sure! Most people seem to struggle as its not in pncconf to my knowledge

There is a full walk through of setting up a 7i76e MPG for a single axis on my build thread starting on this post
forum.linuxcnc.org/show-your-stuff/32029...build?start=20#85279

You can use the same method I used for Axis select as I showed for MPG scale. That way you only need a single MPG
Whilst the 7i76e supports 2 MPG's, I think you can use any inputs via the encoder component (eg. for 7i92)
linuxcnc.org/docs/2.8/html/man/man9/encoder.9.html

One of the positives I saw was that the Mesa cards would allow a more robust industrial 24 volt logic system that was significantly more impervious to noise than lower voltage systems. It needs a lot of noise to invert a signal at 24V!

I believe that the 7i92 only has 5V system and no opto's on it although you can connected to drives as they have opto's but you have to be careful re the inputs without using a BOB I have used one converting a Novamill but used a Chinese bob on one of the ports

Clive, ok getting there,.,.so it seems the 5v system is much more prone to noise than the 24v that makes sense and believe me I had a hell of a time with noise when building this machine. component location and filtration became a real issue. Its s till a little flakey today.

The BOB I have is 5volt. So regardless of what Mesa I choose if that BOB is still in play would I be right in saying the noise susceptibility likewise remains regardless of what Mesa I choose as the 5v BOB remains the weak link?

So it looks to me like the 7i76e does not require a BOB as it has its own opto couplers to cover the required I/O. So the 5V BOB can be discarded altogether for the 7i76e.
The 7i76e also has MPG capability.

If I'm right on all this I think it has to be the 7i76e.

palmac wrote: Clive, ok getting there,.,.so it seems the 5v system is much more prone to noise than the 24v that makes sense and believe me I had a hell of a time with noise when building this machine. component location and filtration became a real issue. Its s till a little flakey today.

The BOB I have is 5volt. So regardless of what Mesa I choose if that BOB is still in play would I be right in saying the noise susceptibility likewise remains regardless of what Mesa I choose as the 5v BOB remains the weak link?

So it looks to me like the 7i76e does not require a BOB as it has its own opto couplers to cover the required I/O. So the 5V BOB can be discarded altogether for the 7i76e.
The 7i76e also has MPG capability.

If I'm right on all this I think it has to be the 7i76e.

I have never used DC brushed servos so cannot comment on what they need. A lot of drives use 5V to control the step/dir but using differential signalling that the 7i76e and 7i96 etc has, is much more immune to noise. They can also cope with 24V stuff for the switches and other controls.

The 7i76e has 0-10v spindle control also with a high speed encoder on it. The 7i96 has the high speed encoder but not the 0-10V but it dose have SSR's for the outputs that can handle about 2A each .

Personally I would go with the 7i76e I believe there are two versions (sinking or sourcing outputs) www.mesanet.com/pdf/parallel/7i76eman.pdf

palmac wrote: So it looks to me like the 7i76e does not require a BOB as it has its own opto couplers to cover the required I/O. So the 5V BOB can be discarded altogether for the 7i76e.
The 7i76e also has MPG capability.

Yes and yes.
4 inputs can also be used as analogue inputs, 1 SSERIAL port, 2 headers for two more daughterboards, just in case you might need them later on to expand.

Its probably worth recapping my take on Mesa's history as a relative newcomer to Linuxcnc. Initially Mesa came up with PCI and PCIe interfaces that contained two DB25 connectors that were parallel port BOB compatible. But then they added two main boards. The 7i76 (step and direction) and 7i77 (0-10v servos) plus a few other boards for extra IO. These boards introduced industrial 24 volt field power for IO.

So then they released the 7i92 which was an ethernet version of the 5i25 and 6i25 and it accepted the 7i77, 7i76 et al.
The next step was merging the 7i92 and a 7i76 into one board (the 7i76e) This single board has basically everything you need for a step and direction system with a spindle.

Then they released a cheaper 7i96 with limited IO (just enough) but no spindle control (except you could set one stepgen up as a PWM that could control the spindle via another external addon board. It can also be configured to put a MPG on some inputs but in my view its hard to give up the IO pins. The cool thing about the 7i96 Outputs is that they each contain a built in opto isolated relay capable of 2 amps or something. The IO pins are tied to a common pin that can be either +v or -v so it supports either active low or active high just by altering the wiring.

Mesa could not do that with the 7i76e so they released the 7i76eD which has active low IO. For a new machine you would typically choose the original Active high version but the D version is handy when interfacing with an existing machine that uses active low switching. Back when I built my machine the D version did not exist so it was easy to make a decision! You might have active low wiring on your machine but also, you might find a lot of relays you are using are going to be stripped out so maybe it does not matter much which way you go.

So with that history in mind, you can see a choice of the 7i92 only moves you part way along the evolution and the 7i76e or 7i76eD is really the best choice for a machine that uses step and direction drives and has a spindle.

You might also like to review Norbert's 7i76e connection sheet if you have not seen it yet.
forum.linuxcnc.org/27-driver-boards/3191...-sheet?start=0#85072