15' (5m) DB25 with Mesa 6i25 and 7i77

Hey guys,

I am trying to complete My VMC retrofit build and need to run a longer DB25 cable than is recommended unfortunately and am trying to figure out a solution that will allow me to do this without changing my setup. I need to use a 15 foot DB25 cable between the 6i25 and 7i77 and was advised against going longer than 10'.

I usually am strict to advise but this would require a massive undertaking in changes to make work in my seetup and wiring that I really don't think I could handle having to do at this point. I was wondering if using a really high end cable such as those used for recording equipemnt which have twisted and double shielded Oxygen Free Conductors and a really high degree of EMI and RFI interference resistance would help allow the longer run of cable?

below is a long to the cables I was considering. they are not cheap so I would want to be fairly certain its a cable that would work first. Can anyone out there help me?

I really appreciate your input!

Chris

hosatech.com/product/dbd-300/

The issue is typically ground noise (from differences in the PC and 7I77s ground)
I would try a 15 foot cable and if that does not work then try the 15 foot cable the 7I77 isolator

The other option is to use a 7I92M instead of the 6I25 since it can plugged directly onto the 7I77
and then you only need a Ethernet cable to go from the host PC to the 7I92

PCW wrote:

The issue is typically ground noise (from differences in the PC and 7I77s ground)
I would try a 15 foot cable and if that does not work then try the 15 foot cable the 7I77 isolator

The other option is to use a 7I92M instead of the 6I25 since it can plugged directly onto the 7I77
and then you only need a Ethernet cable to go from the host PC to the 7I92

Peter,

I think the 7i92m looks like a very good solution. a few questions, am I giving up anything going away from the 6i25 to the 7i92m?

also I have a friend who iconverted the same machine and they ran all their wiring to the front and put the 7i77 near the computer and the 5i25 (I cut my cables to length when connecting everything in there rear cabinet so that is no longer an option for me). he has his machine running and is going to share his files (I'm a Linux newb). Will going to a 7i92m make that no longer possible? it's important because he has the ATC and everything working and I wouldn't even know where to begin.

thanks,

Chris

The main disadvantage of using any Mesa's Ethernet boards is that you must use a different kernel
(Preempt-RT instead of RTAI)

This means you either need to install a Preempt-RT kernel on your existing installation:

linuxcnc.org/docs/html/getting-started/g...th_preempt_rt_kernel

(assuming you are starting the stock LinuxCNC + Debian Wheezy ISO)

or perhaps install the test Debian Stretch ISO ( I would suggest this if you are using newer hardware):

www.linuxcnc.org/testing-stretch-rtpreempt/

In either case there is not much difference in a 7I92+7I77 hal file and a 6I25+7i77 hal file
basically just the card name (7i92 instead of 5i25) and the line that invokes the low level driver
so it should be easy to convert one hal file to another with just a few edits

PCW wrote:

The main disadvantage of using any Mesa's Ethernet boards is that you must use a different kernel
(Preempt-RT instead of RTAI)

This means you either need to install a Preempt-RT kernel on your existing installation:

linuxcnc.org/docs/html/getting-started/g...th_preempt_rt_kernel

(assuming you are starting the stock LinuxCNC + Debian Wheezy ISO)

or perhaps install the test Debian Stretch ISO ( I would suggest this if you are using newer hardware):

www.linuxcnc.org/testing-stretch-rtpreempt/

In either case there is not much difference in a 7I92+7I77 hal file and a 6I25+7i77 hal file
basically just the card name (7i92 instead of 5i25) and the line that invokes the low level driver
so it should be easy to convert one hal file to another with just a few edits

Peter and Tommy light,

Thanks for your advice! I have ordered the 7i92m board as it seems like the best solution.

I don't know what a RTAI or Preempt-RT kernel is t will research it to learn! My friend said he will help as best he can in transitioning his 5i25 machine set up over to my 7i92m setup. If we run into problem or questions arise I will post up in the forum for help.

In the link you sent above it states it is not recommended for production machines, this is a little unsettling, probably because I don't know enough about it. Should I be concerned?

Thanks,

Chris