Where to start with Mesa 7i92 + 7i85S

A couple of things
1. Dont use PWM mode 4, the only thing this will do is swap the PWM and DIR
pins which is just going to add to the confusion (set it to mode 1)
2. As mentioned before, you need to have a 50% duty cycle offset in the PWM and bound the PWM to perhaps 10 and 90%
duty cycle, This will require using the scale component with an offset and using the PID max-output parameter to limits its range

For example set the PWM scale to 100 (so its in %)
add an offset of 50 to the PID output via the scale comp
and bound the PID output to +-40 via the maxoutput parameter

Techrat or Jrjones,

Have you guys had any further progress? I have a ProtoTrak M3 system on my mill, and was looking at doing the conversion myself. Hoping that maybe at least one of you has been able to get everything working.

Thanks

Hi there,

I have had some pretty good success. So far I only have one axis hooked up and operating but that axis appears to be working pretty well. Seeing that all three servo units appear to be identical, I am confident that the remainder will work correctly. I am actually in the process of creating a breakout that will connect the existing cabling on the MX3 to the Mesa board with no modification to the stock wiring. Once this is done, I will report back. I also do want to post up my configuration files to this thread for a sanity check soon. Please let me know if I can answer any questions.

Jeff

Awesome to hear. I would love to get your diagram when you get that finished. I was thinking of doing the same thing. I think taking a serial cable from the existing box where the servos plug in and wiring that to the new driver board (or possibly attempting to stash the driver board inside that box) seems like the simple way to go. I might just get a cheap project box for the driver and mill out an opening for another serial connector and mount that box right next to where the servos plug in.

Have you determined what you are going to do for an E-Stop and how you are going to wire that into the system? My system has the E-stop connected to the main power for the servos so that when you hit the stop, it just cuts the 110v.

Have you determined what you are going to do for an E-Stop and how you are going to wire that into the system? My system has the E-stop connected to the main power for the servos so that when you hit the stop, it just cuts the 110v.

For the time being, I am going to stick with the same E-stop that you currently have. From an "Emergency" Standpoint, it does cut power to the servos which seems like a reasonable thing to do. Down the road, I might consider integrating with both Linux CNC and the Spindle Motor.

Progress Update:

I now have all three axes controlled by LinuxCNC through the Mesa Board. I have put together a breakout board that allows the factory DB37 and DB25 cables to be used to connect the Mesa 7185s to the machine. I probably can refine the PID tuning some but at this time, all 3 axes are moving in the proper direction at what looks to be the proper scale. I still need to mount the Mesa as well as the breakout boards permanently.

The next tasks will be to connecting up Limit Switches and perhaps E-Stop and Jog Wheel. I may look at making some chips to verify that the servos are functional and tuned well before refining the control end of things.

Overall, I am pretty happy with the progress.