Lagunmatic 3516-SX Retrofit

PCW wrote:

The only way that you can damage a 5I25/cable (if the voltage/polarity is correct)
is supplying external 5V to a 7I77 and having the 5i25 set for no cable power (and unlimited 5V current)
This will often damage the 5I25s cable power option jumper

Note that cable power is only good for a few 100s of mA so may foldback due to the on card PTC
if you have any significant encoder load on the 7I77

If you did not get the 5I25/7I77 as a set it's most likely the 5I25 has 7I76 firmware
so will not work with a 7I77 until re-flashed

Firstly - I have to say your customer service is unparalleled! Truly remarkable.

So I have successfully booted my configuration! Feels great. I'm still on the benchtop so no axis testing yet. This is my first time booting an actual config so I have a lot of exploring to do.

I was able to fix my sudo and reupload the 5i25_7i77x2.bit firmware. I also setup my din rail 24v power supply, so I'm feeding external power to both Field I/O and the 7i77 5v. Since I changed 2 things, I don't know what the exact fix was but I suspect it was a firmware issue.

I'm back!

I'm in the process of closing on a lot for a new home build and this machine won't fit in the new garage, so I have to get it up and running only to sell it. T-minus about 9 months...

Firstly: I got the computer in the cabinet:



The computer powered up just fine, and I started LinuxCNC. Right away I got error messages saying Joint 0 through 2 were in the Home position. This wasn't true for any axis, but I was able to clear the message by manually pressing the limit switches.

Next problem I realized was that the servo amp cards had no power. These should be activated through a relay tied to the 'Machine On' pin. I confirmed continuity from the 7i77 pin to the screw at the relay, but cycling Machine On did not activate the relay. Instead of investigating further, I simply bypassed the relay for now.

Once I had power to the servo amps I was hoping I would be able to move the axes. Alas, I struck out again. Jogging all axes results in no discernible response except a Joint Following Error.

Nothing has been easy about this conversion! I'm so impressed by all the other builds out there, a couple really went quick and I've floundered at every step. Pushing forward...

Have you checked that the drives work?
That is, even before you use LinuxCNC or the connect the 7I77 you should make sure that the motors
can be moved by enabling the drives and applying with a small command voltage (say with a 1.5V battery)

PCW wrote:

Have you checked that the drives work?
That is, even before you use LinuxCNC or the connect the 7I77 you should make sure that the motors
can be moved by enabling the drives and applying with a small command voltage (say with a 1.5V battery)

Thanks for the suggestion. All 3 drives were working when I removed the old control in December. Prior to that, I had cut a couple parts using just the control knobs to jog the machine. But I do think it would be a good test to do because I'm not even sure if I am sending signal.

I need to research Halscope and Hal Meter a little more so I can troubleshoot. It would be nice to command a voltage in LinuxCNC and check my output for example but I'm not sure that is possible...

Last night I thought maybe the machine was seized but then I realized I should get an overcurrent alarm on the servo drive. I had experienced that in the past when I discovered by Z ballscrew was seized.

Pncconf can set output voltages in its open loop test tab

Did you look at this servo tuning tutorial:

gnipsel.com/linuxcnc/tuning/servo.html

it has a pretty good list of what's needed and the step by step order to get velocity mode servos moving

PCW wrote:

Pncconf can set output voltages in its open loop test tab

Did you look at this servo tuning tutorial:

gnipsel.com/linuxcnc/tuning/servo.html

it has a pretty good list of what's needed and the step by step order to get velocity mode servos moving

I hadn't seen this page - thank you!!

Learned a little more tonight.

I widened the F error and opened up Halscope hoping to adjust the P value for the servos and and see some movement.

No such luck - I went as high as 200 didn't see movement on X or Y (didn't try Z)

So I figured I'd try Peter's suggestion and manually apply a signal voltage to see what happens. To my surprise as soon as I disconnected the plug that carries the signal and tach the table quickly jumped 5-6" in the X+ direction before the control stopped it due to F error.

That caught me by surprise!

I tried unplugging the Y card and the same thing happened only it moved about an inch before stopping.

When I unplugged Z nothing happened. Hmmmm.. with it unplugged, I adjusted the Balance pot on the card (see attached photo) and was able to very reliably move the spindle up/down. Cool!

When I plugged the card back in, the spindle would no longer react to the Balance pot and it still did not move when I tried to jog it through the control. I did not try adjusting the P value.

I thought maybe if I adjusted the Balance in X I could keep it from running away when unplugged. I turned it CCW a few times and unplugged... the table oscillated. I turned the Signal Gain CCW and it didn't oscillated any longer but the Balance was too sensitive to control the table.

At this point I called it a night knowing I was lucky I hadn't already broke something and need to read more.

You really should never unplug servo interface connections live nor should you operate
the drives without tachometer feedback..

PCW wrote:

You really should never unplug servo interface connections live nor should you operate
the drives without tachometer feedback..

I wish I could say I learn from past mistakes... have certainly caused problems in the past by messing with live connections.

How do you think I should apply a test voltage?

I would (with power off) disconnect the analog signals at the 7I77 end

The reason you should not run velocity mode servos with the tachometer
disconnected is that they will usually run away, perhaps at high speed.
This is because the velocity feedback from the tachometer forms
a PI loop, and without feedback the integral term can increase to full torque
in a short time with just a minor balance error.

An analog velocity mode servo that is enabled, and has its analog input open
(but has tachometer feedback) will typically hold position but drift slowly
(this is normal and OK)

If you apply a small voltage (1.5V would be 15?% of full speed) the motor should
and immediately stop (go back to very slow drift) when the voltage is removed

If you got no response when you ran LinuxCNC (and you have some non-zero P term)
I would suspect a wiring issue. We have seen people attempt to change feedback direction
by swapping the 7I77s AOUT/GND pins at the drive. This will work if the drive has differential inputs
(IN+ and IN-) but will short out the 7I77s analog outputs if the drive has single ended inputs
(IN and common or GND)