Mesa 5i25/7i77 - First Steps

Setting the parameter was a success. I have no idea where I'd have started without your assistance.

Results of dmesg output after running command:
... and "show param", proving that it was indeed set to "4" and the other is still at the default "0":
*Note that I had to exit and restart the HAL session before the change showed up

Now the above didn't actually change the way it counts though. Here's the kicker.... it's a known bug. See thread: using a hand wheel encoder .

The solution given is to use a free high speed encoder.

***EDIT***
I neglected to power cycle the board after reading this, thinking that I needn't bother. Turns out it must have been fixed in the firmware for my recent board. Disregard. Everything is working as it's supposed to and I'm quite pleased.
***EDIT***

its probably just a 7I84 bug
( the sserial remote firmware has not changed for a couple of years )

You always have to cycle power for the NV parameters to take effect
They are copied to the RAM parameters (the ones that are actually used) at power up

Status Update:

I seem to have a working "Hello World" system.

MPG encoder is now controlling the position of the servo, with the servo amp and 7i77 in between the two. I knew to expect trouble when first powering things up because I've been working with these servos with other software/hardware for a while now. So, not too surprisingly it wanted to oscillate itself off the bench. I had mounted it in a little frame/box and put it on a towel to dampen things a bit. This worked ok while I sorted out the initial worts.

I ended up reducing the proportional gain to 0.05 and turning down the gains and current limit on the servo amp. I'll have to do it all over again when it's in the system but for now I'm happy that it works. It follows the commanded position very accurately with no oscillation now. Although it's pretty weak due to low current output for testing. I can crank it up but the oscillations get out of control and there's no point in trying to tune it on the bench.

So I'm thinking my next steps will be as follows:
- Implement E-stop
- Connect drive fault signal and do something intelligent with it
- Connect/configure MPG axis selection and multiplier switches (plus the LED while I'm at it)
- Start looking into what's needed to get this recognized as an axis in LinuxCNC (I have one of these servos already mounted to a small rotary table. That's the easiest to physically work with)

Any suggestions on the best order, or if there are other things I should look at first, are sincerely appreciated.

I only saw this post now.

I made a complete "first steps" here:

www.wiki.eusurplus.com

emcPT wrote:

I only saw this post now.

I made a complete "first steps" here:

www.wiki.eusurplus.com

Great resource. Thanks for pointing it out.

Something I haven't seen yet is what you used for connectors on the outside of your cabinet. Or maybe you don't need them because this is all mechanically joined? I'd like to be able to disconnect the cabinet from the rest of the system to keep it more easily portable.

andypugh wrote:

It's probably time to think about a complete LinuxCNC config now. Use PNCConf to make a basic system, or copy/modify one of the sample Mesa configurations.

Seems logical. It will give me something to do while I wait for some switches and stuff to come from China.

Well, I have a very basic configuration up and running under LinuxCNC. One axis, not mounted to the machine, and it's sort-of, more-or-less tuned on the bench. I can at least do some slow G01 without following errors - of which the maximum is set pretty high still. With the axis scaling, the PID values are way different than when I was running my first simple test. I'm leaving that until I get some limit switches and mount the servo to the machine for actual tuning.

I think this thread has run its course, as I have certainly taken the first steps (and a few more) Mesa with the board. I'll post new topics in the appropriate sections as necessary. Thanks again for all your help.

Sparky961 wrote:

Something I haven't seen yet is what you used for connectors on the outside of your cabinet. Or maybe you don't need them because this is all mechanically joined? I'd like to be able to disconnect the cabinet from the rest of the system to keep it more easily portable.

To many wires. All connected to the cabinet, but with a flexible tube between the cabinet and the operator panel.

Hello Sparky,
Thanx, made for a good read, I am also starting on the computer software and hardware side of things, using the same combination of MESA hardware.

A big thanx to Andy for his feedback, will make life nice and simple.

Cheers,
Beano