Richards wrote: ↑Thu Jan 27, 2022 2:51 pm
I'm interested in learning more about the Kentonsj differential board. I have not yet built a differential prototype for my DMM DNY4 750W driver/servo.
My board uses two TI AM26C31 quadruple differential line drivers to convert the TTL logic from the DB25 to differential. I also added some breakout so that I could combine the enable signals from the screw terminals and take the BKO output from the Z axis drive and faults signals in one neat package. Schematic_Acorn Differential Version 2_2022-01-12.pdf
This board is really just a 4 channel differential converter, it would work with any step/direction drive that accepts differential inputs. I use a DB9 connector and then solder a DB25 connector on the other end to match the DYN4 pins. Here's a wiring diagram of how it interfaces with the Acorn.
Acorn to DYN4 Differential Driver - Terminal Wiring (2).pdf
Here's the cable soldering/pinout for the custom cables.
SJ Thermy-AcornDMM Cable.pdf
This is what it looks like in my cabinet. Each cable runs to the DYN4, no DB25 breakouts and all the signal wires are shielded.
IMG_20190316_113214.jpg
I made and sold a tested board to lavrgs in hopes that it would help him eliminate lost step issues. It seems to have helped him. Keith, Marty and others on the forum have demonstrated that a differential converter is not required. Keith's most recent test from last week proves it isn't required. I mainly made the board to clean up the wiring in the panel, in the process, I designed this board with help from this forum. I thought I may as well take the opportunity to change to differential outputs and make the signal chain more robust. I'm not looking to go into business selling these boards, but I will sell tested boards to interested parties. I can sell you an un-populated board, or a tested board. I have one more design tweak to make on the next revision, I placed the DB9 connectors very close together and only the thinnest of DB9 connectors will work, a little bit more breathing room on that would have been a good idea. I was also dreaming about a re-design to make it strictly a 4 channel converter with no BKO DYN4 support, which would let me use a shielded CAT cable for all the connections, change to all surface mount devices and have a circuit board shop populate the board so I could lower the cost. When you hand solder the through-hole board and all the cables, it's a couple of hours' worth of work. 9 pins are required if you use the DYN BKO output, 8 without. I think a lot of people just use the acorn brake output, I used the DMM one to save outputs for a future tool changer, this was all designed before the ethernet board was available. DM if you'd like more information.
Scott
nice work.
it has always puzzled me why some users have issues with DMM DYN4 and others do not and has made me suspicious (with no proof) that there are some variances in the drives themselves whether it be hardware or software. I am glad you guys are figuring things out for your own particular systems.
I think that’s the case with nearly all drives. One user says works perfect and the next day someone is having issues with the same drive. Just too many variables I guess. Glad to hear there are a few solutions. Seems like the DB25 is the quick and painless answer.
I can report (on my machine) the DYN5 drives do not lose step wired to the headers. That’s not to say another user will get the same results tomorrow.
I am reconfiguring CNC12 after installing kentonsj differential board. I found I had to make some changes from the original setup.
The DMM server setting has the "servo enable active low" box checked - as before. To get the axes to move I had to check the enable boxes in the Advanced area of the wizard - I didn't think they were checked before. I also have a bar over the Input 5 in the diag screen - what does that mean? is it a problem?
I just hacked up a quick prototype using a UA9638C differential driver that I had on-hand to connect the Step and Direction signals from the Acorn to a DYN4 servo driver. I used CNC12's MDI to run tests at X0, X1, X10, and X100 using different feed rates. Using the DMMDRV test program to read the encoder after each move finished, all endpoints were 100% repeatable. There was no bobble. I intentionally made the wiring messy. It didn't matter. The moves were always 100% repeatable. I used Scott's PDFs as a guide. (See his photo's on page 7 of this thread.) I would suggest that anyone who is getting variation with their DMM DYN4 drivers/servos contact Scott. If the demand is great enough, it might be worth his time to make a few boards.
Who is SJTHERMY? Do you mean KENTONSJ?
I have completed my testing and found similar results...I made my first part after adding the differential board and the measured dimensions were +/- 0.001!!!
Yes, KENTONSJ. SJTHERMY is the name in the signature block on one PDF. Scott is the signature at the end of post with the photos. The mystery deepens. What name should we use so that we all know whose boards and cables to use?
Richards wrote: ↑Tue Feb 01, 2022 8:05 am
The mystery deepens. What name should we use so that we all know whose boards and cables to use?
Haha, my initials are SJ and SJTHERMY is the project name I gave to my Thermowood CNC conversion. I guess I should remove that reference from the title block of those drawings:)
I'm glad the board is working for larvgs and that a differential converter will help you out too.
Richards wrote: ↑Mon Jan 31, 2022 6:32 pm
I just hacked up a quick prototype using a UA9638C differential driver that I had on-hand to connect the Step and Direction signals from the Acorn to a DYN4 servo driver. I used CNC12's MDI to run tests at X0, X1, X10, and X100 using different feed rates. Using the DMMDRV test program to read the encoder after each move finished, all endpoints were 100% repeatable. There was no bobble. I intentionally made the wiring messy. It didn't matter. The moves were always 100% repeatable. I used Scott's PDFs as a guide. (See his photo's on page 7 of this thread.) I would suggest that anyone who is getting variation with their DMM DYN4 drivers/servos contact Scott. If the demand is great enough, it might be worth his time to make a few boards.
I thought that CNC4PC had a differential driver board?
IF Scott is amicable he can pass along his design to Arturo Duncan. They can then consider building the board.
Can someone summarize this whole process and what got us here? What symptoms will the board clear up, etc?
Scott?
Marty
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