Hi everyone I start off by saying that i'm just an enthusiast without much knowledge of electronics and kind of got stuck. I'm using NEMA 23 High Torque Motors and they need external drivers (DQ542MA) because the integrated ones in the xPRO do not carry enough current. After a bit of research i found this post by Spark Concepts: Hooking Up External Drivers to the CNC xPRO V3 Thing is, I'm running dual motors on the X axis which for me wouldn't be a problem if only using the xPRO because i'd connect the cloned one to A and job done. How can I run that with the schematics provided by Spark with the external drivers? Can I not use more than 3 motors? Again sorry if i'm being ignorant but i decided it would be best to ask who knows before I make a huge mess Thank you!
The limit is 3 Axes (X, Y and Z), but the motor count is up to you! You can choose to either wire two motors in parallel onto one DQ542MA (For an Axes that has dual motors) or you can wire 2x DQ542MAs and parallel the Signals (from the XPRO - for the axis that has dual motors) so both Drivers get the same step/dir/enable signals. Then each driver can run its own motor. Second option is the more efficient, but requires the purchase of 4x DQ542MAs. You can usually get away fine with the first option though
Thank you for the response! That's what I thought but was worried I would make a mess of it! I think I'll run 4 DQ542MAs to make it more efficient and stable given that I have a couple of them available to me already. I kind of inherited an xPRO V3 from a friend of mine and was building around that and because he told me I could use any motors with it without the need for external drivers. Only realised I actually couldn't with the high torque ones when I had everything else put together already
You can, for now. 2.5A is around 75% of max torque, which is still plenty! Go for it until you outgrow the torque you have, then add drivers (It works)
Hard to say for sure, check the datasheet for your motors, some manufacturers include a torque over current graph in the datasheet. Otherwise trial-and-error. My gut says its too low, you'll be underpowering the motor, and likely get a lot of skipped steps
Thanks for the reply, Peter. I am going to give it a shot this evening. If I the amps are too low. I am going to connect external motor drivers to my xPor v3. I will post a lot of pictures and progress in a new thread.
That one doesnt have an axis for current so won't tell us much. I'd say give it a go if you have the XPRO on hand to test, you can always add bigger drivers if it doesnt work (unless you are trying to save on shipping by ordering at the same time, in which case, get the DQ542ma's - you will never regret having decent power available!)
I got confused trying to wire the external stepper drivers to the CNC XPRO as shown at Hooking Up External Drivers to the CNC xPRO V3 The pictures show the bottom side of the board. I had to solder headers to the board. The board should be shown top side up. How can I calculate the steps per mm?
Hi Jeff, I think it is drawn that way because there isn't any more room on top. The steps per mm is determined by the microstep setting you are using, the type drive (motor and screw or pulley size) you have and using some math.. For example, 1/8 microstep is 8 microsteps x 200(standard steps for most stepper motors) =1600steps per turn, so typical lead screw we use is 8mm per turn so 1600/8 = 200steps per mm.. the math worked out simple because of the 1/8 microstep in this case.. this will get you 99% there, the rest is done with calibration. Cheers Gary
Can external stepper motor drivers go bad? There appeared to be slight burning smell and I thought it came from breakout board shown at PROBOTIX PBX-RF RF Isolated CNC Breakout Board. A few wires came off the drivers while the machine was being moved from the old shop to the new shop. I think that CNC XPRO board isn't compatible with the drivers shown at PROBOTIX MondoStep 7.8 Bi-Polar Stepper Motor Driver. I'm afraid of connecting 48VDC PSU to the CNC XPRO board. I'm not sure if the breakout board shown at CNC USB controller Mk3/4 (4 axis) will work.
Hi Jeff, Yes it is possible to burn them up.. as can any electronic device.. the xpro can not take 48vdc, 24vdc max. The xPro can control those drivers, just like the guide you posted, as can an ($9) Arduino Uno and flash it with GRBL (that's what the xPro runs) or just use Estlcam. Just curious, why the $150 drivers? Cheers Gary
I finally got my CNC router working today using CNC XPRO board. I thought I need the 7.8A stepper motor drivers because the stepper motors that came with the machine are NEMA 34. I used a 12V power adapter to power the board. Now, I need GRBL post processor for VCrave software 9.5. Is 320 steps per mm correct for 1/2" lead screws with 6 TPI?
Hi Jeff, Good to hear you got it working! Depends on what micro-step you are set to on the xPro and what the lead is on that screw. Lead is how far the nut travels on each turn. you said 6TPI that's an odd size for 1/2", if it's a single start screw then that would make it 1/6" per turn (0.1666") or 4.2333mm. At 1/8 microstep (default for xPro) you have 1600 steps per turn.. so 1600/4.2333 = 377 steps per mm. As for the v-carve post processor, on the v-carve website there is an x-carve post that I think would get you going. Then do the calibration. Cheers Gary
I used VCarve to create toolpath to cut a 5" square. I saved the toolpath to GRBL code file. I loaded the file into GRBL Panel. I did a "test" cut in air and I thought it worked on my machine at home. I copied the GRBL post processor to a flash drive. I will try this on the machine at the program. I bookmarked the video so that I can watch it later.
At the program, I used VCarve to create toolpath to cut a 5" square and a 5" circle. I saved the toolpath to GRBL code file. I loaded the file into GRBL Panel. I set the steps per turn at 377 and the square and circle are too big. I set the steps per turn at 320 and the square and circle are a little bit big - about 5-1/8" I didn't have time to fine-tune the machine because the shop teachers need me to make a sign. The sign came out good. My machine has ball screws. I forgot the code for auto-zero and I had to manually set Z axis. The E-Stop doesn't work. Is the E-Stop switch supposed to be NO or NC?
Hi Jeff, I'm not sure what you have then, never seen a 1/2" 6tpi ball screw, maybe a 12-4mm .. but then the 322 doesn't make that work either.. Sounds like you are close, just do the calibration and you will be set. If you already have GRBL g-code output option on V-carve then you don't need any other post processes. this is how you check the micro step setting from the spark-concepts site.. Cheers
The uSTEP jumper settings are set at 8 uSteps. I found out from the Wiki that the Abort/Reset switch needs to be NO and that the E-Stop switch should be wired between the board and the PSU.
I have an USB keypad usually used for people using notebook computers that don't have numeric keypads. I want to use it to jog the machine.
Bad news: On my machine at home, one of the onboard stepper motor drivers on the CNC XPRO board committed suicide while replacing the NEMA 17 stepper motors with NEMA 23 stepper motors. I ordered DQ542MA drivers from OpenBuilds Store.
