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Ah-ha! The 24V field power GND is not connected to earth ground, I was not sure that it should be. That probably explains it then.

Just weird that the machine ran fine for so long.

Thanks, I was getting frustrated with the constantly changing symptoms. I will connect those grounds tomorrow and test again.

Ack!! 40V is a real issue and indicates a grounding problem. This likely
what damaged the step/dir outputs (accidental contact to shield ground would do it)

I would verify that the drive frame grounds connect to earth ground and that the
7I76E ground (24V logic power ground) is also connected to earth ground.

Thanks a lot for your help!

Now that I hooked up an oscilloscope, the problem disappeared completely again - can't reproduce it anymore, at all.

That made generating pulses easier of course, I simply jogged the thing along. The levels of the step+/- pins on the motor side are around 4.8 volts, and -4.8 on a pulse.

I also noticed that the level between STEP- and the cable shield (GND) is around 40 volts AC (50 Hz). I can't say I understand why that would be so. Is that normal/intended?

Perhaps an output is marginal because of previous damage

I would verify full 5V swing on all step/dir pins.

Here is a simple script to toggle all stepgen step and direction pins slowly:

 


Download then

chmod +x stepgens.txt

and

./stepgens.txt to run

Note that this needs a relatively recent mesaflash

github.com/LinuxCNC/mesaflash

Alright, I found out that though the error looks identical, this time the MESA card is NOT the problem. The other good news is that the problem has become reproducible and the Joint Amplifier Failure now always happens immediately during the (attempted) homing procedure.

I can see during the homing attempt that the joint that has the amplifier error attempts to move - the other joint does not. In other words, I think that the servo with the alarm is the good one, and it goes into alarm because it fails to drag the other servo along.

It is still a puzzle though. By swapping port/cables/motors it seems that the common denominator is a port/cable:

 

The red path marks the one that has amplifier error in the different scenarios that I tested.

What puzzles me is that the common denominator in all failure scenarios are panel ports 2 and 3. However, I have measured the every wire several times with an ohm meter (as shown by the green lines in the image), and they are all fine. Since they are also not moving cables I cannot imagine it is a flapping connectivity issue.

So I am a little clueless as to what else I could do now. It seems every potential source of the problem was excluded.

Maybe EMI could have something to do with it, but... why would that suddenly become a reliably reproducible problem after running years with no issue?
Anyway, I also measured all the grounds on the shields of each cable, and they also seem fine/low impedance. (star configuration off of the panel, no loops)

Any ideas what else I can check?

Yes, if the touch probe uses a contact to ground you can use a pull-up
resistor as Andy suggested.

For 7I76XX inputs this needs to be fairly stiff, say 2.2K 1/2W

This is because the 7I76XX input resistance is 11K and needs an input > 14.4V
for a high level at 24V Vfield, and a 10K resistor will not do this.

One way to use a sinking input with a switch-to-ground sensor is to put a resitstor (I would probably try a 10k, choose something that can handle the current that flows when connected between 24V and gnd, anything over 2.5k @ 1/4 W size will be OK). Put one leg of the resistor in the 7i76 input, and connect the other to 24V, The connect the leg of the resistor that is in the input terminal to your switch-to-gnd.
With the switch closed the voltage at the input will be zero, with it open the resistor will pull-up the input and set it true in HAL.

You can invert the sense of the input in the HAL layer to get the right polarity,

Now i think of it, you're probably right. Maybe this is the case. What does imply for my setup / what should i look up so that i don't mess up the connection.

[EDIT]

I think i then have to connect it to GND and input right? (This is more safe, so i can test it first in this setup). I have this simple probe:

www.makerstore.com.au/wp-content/uploads...OOL-TP-V1-6a-NWM.png

Yes, the touch probe should be fine as long as it can be wired this way.

Note that many touch probes have a contact closure to ground, so be careful...
 

Thanks. Yes mine are of the PNP type. And same goes then for the input of the Touch sensor? This is not a PNP. This acts more like a mechanical switch.

That looks basically OK

If you have PNP type sensors, you do not need any additional interface components
that is the sensor output goes directly to the 7I76EU input.

7I76XX inputs are quite rugged, they need no additional protection.

 

Hi All,I’d like your input on my planned setup.
As I mentioned in my previous post, the latency on my new machine was so high that I had to switch from the parallel port to a Mesa card. Earlier this week, I received a Mesa 7i76EU board. It looks awesome—if a bit overwhelming at first glance!My plan:

• Motors:
  I’m using 3x Longs DM542A stepper drivers, which I plan to connect to Stepper 0/1/2 outputs on the Mesa board, using what I believe is called a “single-ended” wiring configuration. My plan is to connect +5V to the ENA+, DIR+, and STEP+ on each driver, and wire the ENA (5V), DIR-, and STEP- of each driver directly to the corresponding outputs on the Mesa card.
• Spindle:
  I have a Huanyang VFD 1.5KW for spindle control. For now, I’ll keep my Modbus-over-USB setup, which seems to work well enough. I’ve read that getting Modbus running directly on the Mesa board requires a bit more advanced configuration, so I’ll save that for later.
• Homing Sensors (Capacitive, 3x):
  My plan is to connect the +24V supply to the positive (brown) wire, and field ground to the negative (blue) wire of each sensor. I intend to connect the sensor output (black) wires to Input 1, 2, and 3 on the Mesa card.

Questions:

1. Current-limiting resistor for home sensors:
   For the capacitive homing sensors, do I need to add a resistor between the output pin of the sensor and the Mesa input to protect against overcurrent? In the past, I’ve blown a few sensors and started using resistors to protect them, but those were cheap sensors—the Mesa card isn’t!
2. 2-wire touch probe:
   For my two-wire touch-off probe, I plan to connect one side to +24V field power and the signal wire to Input 4. Here too, should I add a resistor to avoid potential shorts or overcurrent situations?

Bonus questions:

• Any recommendations for best practices when wiring sensors and stepper drivers to the Mesa 7i76EU?
• Are there things I should definitely avoid to protect my Mesa card or improve reliability?
• For those who have set up Modbus on the Mesa board, how steep is the learning curve compared to using Modbus over USB?

Thanks for your advice and experiences!

Hallo zusammen,

ich plane aktuell eine Sammelbestellung für Mesa-Karten (z. B. 7i76e, 6i25, etc.), da sich bei größeren Stückzahlen häufig günstigere Konditionen ergeben – sowohl beim Preis pro Karte als auch beim Versand.

Rahmenbedingungen:

Ziel: mindestens 10 Karten

Bestellung erfolgt gesammelt direkt beim Hersteller
!!!Vorkasse notwendig, damit ich nicht auf den Kosten sitzen bleibe!!!
Ich übernehme die Organisation und den Versand innerhalb Deutschlands

Preise sind noch nicht final, je nach Anzahl & Modell

Wer Interesse hat, bitte folgende Infos per E-Mail an "This email address is being protected from spambots. You need JavaScript enabled to view it.":

Betreff: [Name, Vorname]   [Modell]  [Anzahl]
z.b.:      [Lauterbach, Elias] [7i76e] [3]

Als Text dann den Versandort (Packstation Möglich)

Alles weitere erfolgt dann per E-Mail

Wenn wir genug zusammenbekommen, gebe ich die finalen Preise bekannt und sammle dann das Geld ein, bevor bestellt wird.
Ziel ist eine faire, transparente und zügige Abwicklung.

Viele Grüße
Elias Lauterbach

Something like:

loadrt or2
addf or2.0 servo-thread

net probe-wzl  <= hm2_7i76e.0.7i76.0.0.input-08-not => or2.0.in0
net probe-3d   <= hm2_7i76e.0.7i76.0.0.input-09-not => or2.0.in1
net probe-in     =>  motion.probe-input <= or2.0.out

Notes:

This assumes the "or2" is not already used

(if its already used, you need to add a new instance with the names or count stanza)

Also not sure of the individual 3d and wzl polarities

PCW, thanks a lot for the advice with the smaller resistor! I found one 2.2k with 1W in my boxes and used that today and voilá, it works as it should. Problem solved, I hope. (Don't know if I need noise reduction)Guys, I have no idea how to use sth like mux or mux_generic. I wouldn't even be able to use two inputs - but just out of curiosity , how would you do that in a HAL file if i would use an OR2:
 loadrt or2 count=1
net probe-in     <=  hm2_7i76e.0.7i76.0.0.input-08-not    
net probe-in     =>  motion.probe-input
and the second input hm2_7i76e.0.7i76.0.0.input-09 ? my programming scills are beginner level...
(Yes, I read the example in the LCNC HAL Examples to OR2 but I cannot convert that for my problem.)

Thanks and best regards!
Hanno