Screw Terminals vs DB25 Header

[qjones]

I had some very odd issues with my machine and losing steps on direction reversal. A very predictable amount that would accumulate when I was jog back and forth in incremental it would slowly drift. I think I have now got this sorted but while I was debugging it led me into something I am seeking clarification on. I am using Leadshine MA860H stepper drivers on my mill. I have it wired as this configuration with +5V from my power supply going to all the + connections, and the - connections driven from the centroid board with resistor being "0" ohms:

When I was digging in further I noticed that most of the schematics to other leadshine drivers showed to use the DB25 port. Also on the forums it looks as if anyone has trouble with the motor drivers that the answer is to NOT use the header connections? I realize the technical difference is open-collector vs a 5v push pull configuration but the drivers should support either.

Again I think I have it sorted for now but I am making sure I am not missing some underlying assumptions with how the controller drives the steppers.

Thanks,

[Gary Campbell]

Two things, and this gets repeated over and over again. LeadShine drives (for the most part), but your DM-860 models in particular, should be connected to the DB25 header. There are numerous ways this can be accomplished but my preferred method is to use the step & direction for each drive to the step+ & direction+ terminals, connect the step- & direction- to one of the DB25 ground terminals and to invert the step & direction signal on the advanced page. I also set the step pulse frequency to 100,000 via parameter 968=12.

Do it, it works

[Richards]

If you have access to an oscilloscope, check the signals using the H2/H3 connectors vs the DB25 connectors. I ran tests the other day, first with a DM542 driver connected through the H2 header (24VDC going through a 2,2K resistor to the (+) sides of Step and Direction and the (-) sides of the Step and Direction signal connected to Step and Direction on the H2 connector). The signal was good and the stepper driver moved the motor as expected. Next, I connected +5VDC to the (+) step and direction terminals on the DM542 and connected the (-) step and direction signal to the DB25 connector. After inverting the signals through the Wizard and changing the PPS to 100,000 steps via the Acorn's setup screen, the DM542 driver moved the motor. The scope showed some ringing on the DB25 signal (+/- 0.75 volt at signal start tapering off to 0.25v after 1.5 uS, but no ringing on the H2 signal. The ringing did not seem to have any effect on the motor's performance except that I had to drop the pulse rate from 200,000 PPS to 100,000 PPS - not a big deal for anything that I might build. Both the H2 and the DB25 header connections moved the motor as expected.

Based on that test with my Acorn board, I'll use the H2/H3 connections with the appropriate current limiting resistor. The ringing could be cancelled out by adding a small value capacitor to the signal if it became a factor on a production machine. Please note that the motors did NOT miss steps or show any erratic behavior, regardless of which connector I used.

I ran the test because Gary Campbell sent me two DB25 connectors so that I could easily connect to the DB25 connector and because I was curious.

[cnckeith]

for your reference.. the _rev4 spec manual has added information about the difference between the DB25 and Screw terminals.
http://www.centroidcnc.com/centroid_diy ... manual.pdf

same holds true for _rev3 boards as well.

[qjones]

Yikes. Again some conflicting use cases. I'll have to leave it wired as is on screw terminals for now and it is working. I need to do a few more endurance test just to make sure I have no missed steps on direction reversal. In my config I had inverted the Direction on the advanced page to flip the direction my motors were spinning. I am certain now this was in error and changed it back to non-inverted and switched the axis direction reversal parameter to "Y". I should have realized that sooner.

Unfortunately I have a bit of a hybrid stepper/servo system currently. My Z-Axis is a DMM Dyn4 AC servo which from my understanding must be on the screw terminals to drive it correctly. Which means I can't run my steppers off the DB25. The way I see it in the wizard it is one or the other. Good news is I plan on replacing X/Y to be servos soon as well and this should no longer be an issue. I am just seeking deeper insight into the intent between the different interfaces for further knowledge later on/different machine setups.

Thanks,

[Richards]

Don't let me scare you from using the DB25 connector. I live in a world where the test bench rules. The acid test is whether the device functions when used in the field. When so many people are using the DB25 connector instead of the H2/H3 connector when using 5VDC, it must work in the field. I manage to tick off a lot of people who might wonder why I prefer the test bench over a real machine. It's not that I prefer the test bench, but when most days I limp around with a walker or at least a cane and usually after an hour or two on the computer, my degraded eyes stop being able to see clearly, the answer is that I'm just not agile enough to be around equipment where a careless move could cause grief, so I do what I can do safely at the test bench.

If the DB25 connector is easier to use for your application, don't be afraid of it. If using the H2/H3 connectors at 5VDC with no additional resistor for many stepper drivers works, don't be afraid to use it. If you prefer to use 24VDC and your drive uses an opto-coupler that specifies 5-10mA, then you can use the H2/H3 connectors by adding a current limiting resistor in series with the signal. Just use ohms law to determine the resistance value, i.e., (24V - 0.7V for opto-coupler) = 23.3V. 23.3V / 0.01A = 2,330 ohms. Use the closest standard resistor, i.e., 2.2K.

In my testing and with my DM542, G203v and G540 stepper drives, I could use the DB25 connector with 5V or the H2/H3 at 24V with the appropriate.

[Commotion]

I set my rev2 acorn board up to leadshine ac drives using a 5v source connected to + connections on drive and - connections on screw terminals... as per the diagrams presented back then. It works well with max frequency set to 400kHz but actual max is limited to 200kHz by set max rapids and electronic gear ratio. Anything more than 200kHz and I would loose steps. The leadshine drives were happy with the short pulse duration of the 400kHz setting so I left it at that.

On the rev3 board for the lathe I used the db25 connector as per the diagrams to connect some leadshine dc servo drives. When connected to the db25 connector it won’t run on the 200kHz setting at all but does run on the 100kHz setting. Before I got the rev3 board I tried it on the rev2 board on the screw terminals but after it not working I then dropped frequency from 400 to 200 and it worked. I didn’t get around to seeing if the rev 3 board would run the drives at 200kHz on the screw connectors as 100kHz was fine for what I needed anyway and I like the neatness I’d rhe db25 connector. I had issues with the drives faulting so I have sent them back for a refund and will likely try a different brand of drive.

[tkbot47]

I have a rev 3 board wired to Leadshine HBS860H closed loop hybrid stepper drivers, using the screw terminals, running at 200khz, and have not noticed any lost steps or erratic running so far. I followed the then-current wiring diagram for Leadshine, which showed wiring to screw terminals for rev 3. That diagram is now under legacy ver 2, and the title no longer says rev 3. Rev 3 and 4 show other Leadshine model number drivers hooking to the DB25.
Questions: Is screw terminal wiring still appropriate for my particular drivers, since the model is not specifically mentioned in the prints, or should I be changing to DB25, even though they've worked OK. What changed for rev3 to now recommend that most Leadshine drivers should be wired to DB25, especially running at 100khz?

[Gary Campbell]

All of the LeadShine drives are created equal. Some are newer designs and they do very well with the H2/3 open collector connection. That said many of the LeadShine clones (yes the Chinese hack the Chinese) that are sold via Amazon, eBay and others for less money are not the same products that I purchase from LeadshineUSA. I may pay more, but I have both warranty and support.

To compare prices look here at the USA Leadshine factory outlet: http://www.americanmotiontech.com/

[tkbot47]

Gary, the drives I got (with a NEMA 23 stepper) were indeed Chinese Ebay. I wired them directly to the screw terminals - no resistors - per the Centronics wiring diagram available at that time. Would I do better to wire them to my rev 3 board through the DB25 per one of the current diagrams? I ask because this particular model is not listed on the prints, so it's not clear what is considered good practice now, or if resistors are required or not.

Like I said, things seem to be working OK as is. I've added a pic of the driver. The opposite side has a fan cooled heatsink. I also included a copy of the wiring diagram I used that was current at the time.