Another DYN4 and Acorn Losing Steps Issue

[martyscncgarage]

... If there is an issue, collectively it's worth all of us trying to replicate and subsequently solve the problem.

You had the problem, but why?

Marty

I agree. This is why I went to great lengths to perform the same test, changing one thing at a time until the problem went away. I test and troubleshoot for a living. As I have stated before, I was posting my results in hopes of helping the manufacturers, and others experiencing the same lost steps problem. While I do not know the cause, it is apparent the DYN4 works well with the DB25 step/direction signals on machines it has problems with the screw terminals. The why.. I don't know.

Again, my intention is to contribute to this community.

Absolutely. No worries.
Your experience is definitely appreciated. Always the end goal is to track down the culprit if one exists and definitively address the issue.
Marty

[qjones]

Just so I am clear DMM admittedly agrees to there being an issue with their schematic and their cable with the current resistor value? And what is recommended is the +5V/no resistor and the centroid schematic at the moment? I have not verified I actually have the issue. I am going to hook up the encoder this weekend and verify. But there was some strange behavior that seemed like a subtle missed steps issue and I was using the DMM schematic and 24V.

[martyscncgarage]

Just so I am clear DMM admittedly agrees to there being an issue with their schematic and their cable with the current resistor value? And what is recommended is the +5V/no resistor and the centroid schematic at the moment? I have not verified I actually have the issue. I am going to hook up the encoder this weekend and verify. But there was some strange behavior that seemed like a subtle missed steps issue and I was using the DMM schematic and 24V.

Not the schematic, the resistor value. I am waiting to hear what the new value is. I suggest you give them a call.....

[Dan M]

I have to wonder and think that it has to do with the cable length. The op has a big router and the drivers are remotely mounted, if my little router with the electronics mounted to the table has 15' long cables his have to be 25-30' long. Maybe it's as simple as undersized wiring or bad solder joints since I'm sure he had to extend the factory cables. Or does DMM make them to length for you? I'm sure that the resistor's being oversized as well compounds the problem when the cable length is increased. Just some simple things to think about with trouble shooting the issue.
Has any one checked for current drops and continuty with the extended cables?

Dan

[slodat]

I have to wonder and think that it has to do with the cable length. The op has a big router and the drivers are remotely mounted, if my little router with the electronics mounted to the table has 15' long cables his have to be 25-30' long. Maybe it's as simple as undersized wiring or bad solder joints since I'm sure he had to extend the factory cables. Or does DMM make them to length for you? I'm sure that the resistor's being oversized as well compounds the problem when the cable length is increased. Just some simple things to think about with trouble shooting the issue.
Has any one checked for current drops and continuty with the extended cables?

Dan

The motor power and encoder cables are unmodified, as they came from DMM. 10m long. They also offer 15m length. It's not undersized, or bad solder joints. I didn't extend the cables. The resistors in the DB25 are being changed to 1k, according to the email I received from DMM last week.

The issue, once again, is steps are being dropped between Acorn and DYN4 when connected to the screw terminal step/direction inputs. I tested the motor/drive connection (using DMM"s software to move the axis) and lost no encoder counts. The only thing that resolved the issue was switching the step/direction to the DB25 and +5vdc for the associated power. ALL of this is well documented, in this thread. It is beyond me why this information isn't actionable, yet all of the conjecture and "the schematic works for me" is the continued response.

Guys, it doesn't work. I'm not the only one. I'm just the one speaking up. My PM inbox is full of offline conversation where others are seeing the same problem and they are using the DB25 step direction to eliminate the lost steps. Just sayin. If you want it to work, perhaps try using the configuration that is working for me, and others.. It would be cool if the manufacturer's (who most likely have the test equipment needed) would take a look and see? While I get paid to do this sort of thing at my day job, I don't own an oscilloscope any more..

[Dan M]

I just don't understand why different brands of drivers have issues. I'm running Gecko 214 drivers hooked up to the screw terminals and pulling the 5 volts from the Acorn power supply. I'm running 25000 steps at 400KHz and I haven't had one issue with anything. No lost steps all my job's are perfect 900ipm rapids flawless motion. I just don't understand what is different with my setup vs someone else's? I don't see how it could have anything to do with the Acorn board. Maybe you have been talking about DMM needing to check it out? I honestly don't see why it would be Centroids responsibility since they don't make the motors and drivers? Considering out the gate you had a bad motor and encoder, in my opinion whatever is going on has nothing to do with the Acorn. I'm curious to see what is causing all these issues that seem to be popping up lately with lost steps. It's just so strange that some people are having the issue and others are not.

Dan

[kentonsj]

I am in the process of bench testing my Acorn and DMM DYN4's. I haven't noticed any particular lost step problems yet. I have tried with connections to the DB25 and to the screw connections. I think we need to have some electronics expertise lean into this discussion. I would encourage that responses to questions offer a technical response. It's obvious this isn't a case of someone not knowing how to read a schematic or wire to a schematic, we need real meat and potatoes discussion. There is usually more than one way to accomplish something, but in this case there is surely the best way to do something. The best way, in my opinion, offers the most robust signal path between the Acorn and motion drive possible.

The DB25 connector uses a push-pull driver and operates at 5V. The screw headers use open collector outputs. Are there inherent differences in the electronics that would help explain what Slodat is seeing? Is the particular push-pull driver on the Acorn better suited to 400kHz and DMM combo than the open collector outputs? The difference between success and lost steps in Slodat's case was to move the step signal from the open collector to the push-pull driver, why?

[slodat]

A snippet from my dialogue with DMM last week:

"We think we have identified the cause. It's most likely the current flow through your board is not enough so we will send new cables with smaller resistors installed to increase the current flow."

I opted to not continue to troubleshoot the issue as I need my machine running and making parts.

[Gary Campbell]

Look Guys...
Each of these electronic components has its own value and "electronic personality". On paper they all seem to say they are compatible, but in real life, not so much. Different models from the same company react differently to the same signal.

Drives I am familiar with do NOT operate the same on Acorn, WinCNC, UCCNC or ShopBot controllers. Again, they all appear to be perfectly compatible on paper. I am used to it. For as long as I remember there has always been a bit of trial and error. That's why I own a 'scope.

It seems to me, and I could be wrong, but there seems to be a bunch of inconsistency in the operation of both Gecko drives and DMM servos. As popular as they both seem to be, I cant imagine that one of their (the mfgr) techs hasnt done more. I also assume that many of these problems can be created by inexperienced users, which could be why the mfgr seems to only be there after a user forum finds an issue with the last recomendation.

Now you know why I recomend other brands.

[mick41zxr]

Slodat,
My system repeated exactly what you were describing.To they eye it appeared to be working normally but when I crashed a home/limit hard it prompted be to check. Via the DMM monitor there was enough variance to be over 5mm off. Cable were constructed with 5v power supply no resistor.
Now moved step & direction to the DB25, via the monitor getting no more that +/-6 position counts (+/-0.0005mm).
This is with rapids set at 12000mm/m (472 inch) accel at 0.3 sec for approx 100kg load.
Thanks
Michael