Cuts not repeatable, I'm losing steps

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lavrgs
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Re: Cuts not repeatable, I'm losing steps

Post by lavrgs »

ShawnM wrote: Sat Jan 08, 2022 12:14 am You can "IMPORT" the drive settings on the "Axis Drive Type" page in the wizard. There's a button at the bottom of that page.

Thanks for doing this Keith. Hopefully this is the answer for those missed step issues that have plagued so many for so long with the DYN4. As slodat has stated he's been running his machine with no issues on the DB25.

I will forward you the DYN5 drive settings and schematic I created when I have everything tested and working.

Today I tested 2 of my 3 DYN5 drives with the Acorn and wanted to report back some news. Once I powered them up I ran the Auto Tune just to have a base line for the axis. I have the drives wired to the headers (the DYN5 has both 5v and 24v PUL and DIR inputs unlike the DYN4) to test for lost steps. The step rate is set to 400,00 steps/second in the wizard. I have the axis max jog rate set at 600 IPM. I created some g code that did the same as lavrgs did, I moved from 0 to +2 then to -2 about fifty times then return to 0 at the end. With the DMMDRV software running the "live trace" I ran the g code. It came back to the exact same encoder position EVERY time. I ran this test 4 or 5 times to be sure. Both my Z axis, which currently weighs about 70 pounds with an air assist ram) and my Y axis ran perfectly with no lost steps from the headers. The encoders both came back to the same starting count on every test. I have a video I made of the Y axis with my iPhone but after watching it myself it makes me a bit nauseous just watching it. :shock:
Excellent news!!!
lavrgs
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Re: Cuts not repeatable, I'm losing steps

Post by lavrgs »

A couple questions about the wiring; I have a 5vdc supply is there any reason to use it over using the Acorn supply?
In my discussions with DMM their connection scheme varies from the Centroid draft schematic.
They suggest
Acorn DB25 Pin 2 Step1 into DYN4 Pin 11 PUL+
Acorn DB25 Pin 18 COM into DYN4 Pin 23 PUL-
Acorn DB25 Pin 3 Direction1 into DYN4 Pin 22 DIR+
Acorn DB25 Pin 19 COM into DYN4 Pin 10 DIR-
Richards
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Re: Cuts not repeatable, I'm losing steps

Post by Richards »

Page 17 of the DMM DNY4 manual (REV. ZM5-A18A) shows that the Step and Direction inputs to the DYN4 drive use opto-couplers. Pins 11 and 22 are the Anode (+) side of the opto's diode. Pins 10 and 24 are the Cathode (-) side of the diode. The Acorn's DB25 connector can be used to Source or Sink the signals.

If the Acorn SOURCES the signals, then the Step pin (2,4,6,or 8) would be connected to DYN4 DB25 pin 11 and DYN4 DB25 pin 23 would be connected to GND. The Direction pin (3,5,7, or 9) would be connected to DYN4 DB25 pin 22 and DYN4 DB25 pin 10 would be connected to GND.

If the Acorn SINKS the signals, then DYN4 DB25 pin 11 would be connected to +5VDC and Acorn's Step pin (2,4,6,or 8) would be connected to DYN4 DB25 pin 23. DYN4 DB25 pin 22 would be connected to +5VDC and Acorn's Direction pin (3,5,7, or 9) would be connected to DYN4 DB25 pin 10.

You will note that if there is voltage between the (+) and (-) inputs, the internal opto-coupler will be ON. If there is no voltage between the (+) and (-) inputs, the internal opto-coupler will be OFF.

In the Circuit Example section of that page, you'll also see a circuit that uses a differential line driver. The circuit looks interesting to me. I've just ordered some parts from Digi-Key to see if using a differential line driver eliminates noise. I'm attaching my first draft schematic in case someone else wants to try out the circuit. I used KiCad software to generate the schematic. EDITED: I blindly used a part from the KiCad library without checking it against the data sheet. The part in the library is WRONG. The part to use is a UA9638CP. I changed the schematic to show the correct part. I've added a 4N25 opto-coupler to signal a servo fault to the Acorn. The Acorn's DB25 connector does NOT provide an ENABLE signal. The ENABLE signal from the Acorn's "H" headers needs to be connected to DYN4 DB25 pin 15 and DYN4 DB25 pins 1 and 5 need to be connected to GND. DYN4 DB25 pin 16 sources 24vdc to the "H" connector on the Acorn. DYN4 DB25 pin 5 completes the external opto-coupler's FAULT. That opto-coupler turns ON if the servo faults. If anyone decides to try out the circuit, please spend some time and verify the connections before powering on. I've only spent enough time studying the manual to get a feel for the signals. Further study will be necessary after I get the parts.

THE SCHEMATIC HAS BEEN CHANGED
.
UA9638CP.png
Last edited by Richards on Thu Jan 13, 2022 4:59 pm, edited 1 time in total.
-Mike Richards
lavrgs
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Re: Cuts not repeatable, I'm losing steps

Post by lavrgs »

I'm trying to do a test run on the X Axis using the DB25 connections per the draft schematic. I'm using the XML file posted above and am having some trouble - it may be as simple as having to invert the signal in the wizard...how do I do that?
Via MDI I can only move +X
Attachments
report_402E71CADC40-0323214550_2022-01-11_12-29-48.zip
(697.89 KiB) Downloaded 2 times
Richards
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Re: Cuts not repeatable, I'm losing steps

Post by Richards »

You can invert the Step, Direction, and Enable signals in Wizard. Go to Axis -> Advanced. You'll find "Axis Signal Inversion" with a check-box for Step, Direction, and Enable for each axis. I know that I had to check or uncheck those boxes when I was experimenting with using +5VDC or GND as common with some stepper motor drivers.

Also, under Axis -> Configuration, you'll find the setting "Direction Reversal" that you can set/reset if an axis moves in the wrong direction.
-Mike Richards
lavrgs
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Re: Cuts not repeatable, I'm losing steps

Post by lavrgs »

Richards wrote: Mon Jan 10, 2022 3:28 pm

If the Acorn SOURCES the signals, then the Step pin (2,4,6,or 8) would be connected to DYN4 DB25 pin 11 and DYN4 DB25 pin 23 would be connected to GND. The Direction pin (3,5,7, or 9) would be connected to DYN4 DB25 pin 22 and DYN4 DB25 pin 10 would be connected to GND.

If the Acorn SINKS the signals, then DYN4 DB25 pin 11 would be connected to +5VDC and Acorn's Step pin (2,4,6,or 8) would be connected to DYN4 DB25 pin 23. DYN4 DB25 pin 22 would be connected to +5VDC and Acorn's Direction pin (3,5,7, or 9) would be connected to DYN4 DB25 pin 10.

You will note that if there is voltage between the (+) and (-) inputs, the internal opto-coupler will be ON. If there is no voltage between the (+) and (-) inputs, the internal opto-coupler will be OFF.

.Screenshot 2022-01-10 114540.png
I'm not familiar with the difference of SOURCING and SINKING - is this based on the wiring you described or is there something more to it? When you say GND do you mean COM or is it chassis GND?
tblough
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Re: Cuts not repeatable, I'm losing steps

Post by tblough »

Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
Richards
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Re: Cuts not repeatable, I'm losing steps

Post by Richards »

Tom,
Thanks for posting the site about Sinking and Sourcing.

Lavgrs,
After reading the information that Tom posted, Sinking and Sourcing should be easier to understand. Read that information until it makes sense because you'll need to understand Sinking and Sourcing to properly use the Acorn.

You can connect the Step and Direction signals from the Acorn's DB25 connector so that the Acorn either Sources current or Sinks current. If you use the connect the auxiliary 5VDC power supply to the Step(+) and the Direction(+) terminals on the stepper/servo driver, then the Acorn must SINK current from the SOURCE (+5VDC) by connecting the Acorn's Step and Direction signals to the stepper/servo driver's Step(-) and Direction(-) terminals. When the Acorn gives a Step signal, it pulls current from the +5VDC power supply through the step sensor in the stepper/servo driver.

The opposite happens when the Acorn is used as the SOURCE of current. In that case, the Step(+) and the Direction(+) terminals on the stepper or servo driver are connected to Step and Direction on the Acorn's DB25 connector and the stepper/servo driver's Step(-) and Direction(-) terminals are connected to GND. GND (Ground) is the Common or Ground terminal on the power supply (or the Ground pins on the Acorn's DB25 connector). GND is the reference point used to measure voltage from a DC power supply. In this case, the Acorn SUPPLIES or SOURCES current to the stepper/server Step and Direction terminals. Current flows from the Acorn through the stepper/servo sensors to GND.

The Acorn can be used either way. Both ways have worked equally well for me. All I had to do if the motors did not move when commanded was to use Wizard to change the polarity of the signal (as described above in a previous post).
-Mike Richards
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