[jandan]

Hi,

I'm new in building a CNC machine and feel little embarrassed of my ignorance. My mill is now built (no spindle yet) and the axis seams to work fine (from my current and limited test) and they have been homed for the first time (XYZ, ball screws, Nema 23 425 oz motors, combined limit and home switches). I run the system with LinuxCNC.
The drives is DM542A, peak 4.2A, max 128 microsteps and a controller board. All including the mechanical parts is from China. Not much of documentation and info, it took a while to test and figure out the wiring. Still I'm not absolute sure if things are correct connected and the parameters in LinuxCNC are defined in the proper and best way. My main concern for now (I expect more to show up) is the parameters for Step Time, Step Space, Direction Hold and Direction Setup in the Stepconf interface. I requested parameters from China and they sent me some info that I can't translate to the parameters in Stepconf. My current parameters seams to work fine but they are based on wild guessing from drives that could be close to mine (Step Time 5050 ns, Step Space 5050 ns, Direction Hold 500 ns and Direction Setup 500 ns). Can someone help me to translate the Sequence control signals (DIR/PULS MODE) from Longs Motors to the Stepconf parameters? They are:
Width of PULSE 1.0 us, Width of PULSE space 1.0 us, PULSE frequency 500 KHz and time of change DIR 2.0 us.

Attachment 199994

Thanks in advance
Jan Dansson
Sweden


Link for electronics here, shipped from Europa to Sweden:

SHIP from USA WH 3Axis Nema23 Stepper Motor 425oz in 3 0A for CNC Controller Kit | eBay

[lwill]

From LinuxCNC Documentation Wiki: Stepper Drive Timing
"Multiply microseconds (us) by 1000 to get nanoseconds (ns)"
Step Time = 1.0 x 1000 = 1000ns
Step Space = 1.0 x 1000 = 1000ns
Change Direction = 2.0 x 1000 = 2000ns
From the diagram it would appear that Direction Hold and Direction Setup are each ~1/2 Change Direction, or 1000ns each.
*This is just my best guess. I think Time and Space are right, but the last two may need to be adjusted if you have problems. (I believe latency may come into play)

This one looks very similar to the one you bough: (so many are made in the same place with different names)
http://leadshineusa.com/UploadFile/Down/M542V2m.pdf
and from the Linuxcnc wiki page it lists the settings as: 1500 1500 8000 5000
which is much more conservative than the diagram you have but should be in the ball park for starters.

It would be better to ask in the Linuxcnc area.

[jandan]

Thanks iwill for your reply and comments.

This drive also looks the same:
Aliexpress.com : Buy Best selling! wantai DQ542MA stepping motor driver 18 50V/4.2A/ 128 Micro from Reliable stepping motor driver suppliers on Wantai Motor 's Store
and its listed here to:
LinuxCNC Documentation Wiki: Stepper Drive Timing
I used the listed parameters from here on my drive but the numbers now looks strange in some way.
My request was also posted at LinuxCNC.

Jan

[jandan]

Thanks fore the timing parameters.

Should I add something for the Break out board with optical couplers (estimate, not much spec available) ?

[doorknob]

Thanks fore the timing parameters.

Should I add something for the Break out board with optical couplers (estimate, not much spec available) ?

The DM542A driver already has built-in optoisolators on the input signals. So it is not necessary for you to use a breakout board that also has on-board optoisolators. It is not generally recommended to drive one optoisolator from another one because it could lead to "softening" or slowing of the signals.

Having said that, if you can identify the part number for the optoisolators on the breakout board then you should be able to look up the part specs in its datasheet.

Some optoisolator parts may be faster than others, so if you have slow ones, then it might be necessary for you to modify your timings to take that into account.