The "Ruppe" Test: DMM DYN4 Encoder signals piped into Acorn's Spindle Encoder

[martyscncgarage]

Terry Ruppe of Arrow Controls came up with the idea.
I decided to give it a go on my Emcoturn 120 lathe fitted with DMM DYN4 AC drives.
Seems an accurate way to test for lost/gained steps as the encoder is providing feedback to Acorn to display.
You do have to make up a cable that matches the DYN4 encoder pins(or any other drive that provides standard encoder signals) to the Acorn Spindle encoder pins.


https://youtu.be/NQrgwdAZK9s
https://youtu.be/NQrgwdAZK9s

[ScotY]

That’s very interesting, Marty. I haven’t been hanging out here much lately so wondering if there was a reason for the test? Being a quality servo, wouldn’t you expect no error? I think it would be equally interesting to run the same test at a lower feedrate. On those rapid moves, you can see the encoder signal lags behind, as one would expect.

Question...if you ran a program at a very high feedrate and one axis had to move significantly farther than the others, would an error be introduced in the part? Hope that makes sense?

[cut2cut]

Hey Marty,

Thanks for making the video. Any chance you could include the wiring diagram for the cable specific to the DYN4 and Acorn ?

Cheers,

Jake

[cnckeith]

on a related note acorn to dyn4 using the DMM purchased and make your own cable schematics are in the latest Acorn schematic set

http://www.centroidcnc.com/centroid_diy ... matics.zip

and Acorn to dyn4 setup sheet is attached.

DYN4 Acorn setup.pdf

(665.63 KiB) Downloaded 170 times

[martyscncgarage]

Hey Marty,

Thanks for making the video. Any chance you could include the wiring diagram for the cable specific to the DYN4 and Acorn ?

Cheers,

Jake

I can, but its pretty straight forward. Go to the DMM DYN4 manual, look for the DB9 connector, it has the encoder output signals, match them up to the Acorn encoder input signals.
Be sure to use a shieleded twisted pair cable and solder the drain wire to to the DB9 shell on the Acorn side.

[cut2cut]

Hey Marty,

Thanks for making the video. Any chance you could include the wiring diagram for the cable specific to the DYN4 and Acorn ?

Cheers,

Jake

I can, but its pretty straight forward. Go to the DMM DYN4 manual, look for the DB9 connector, it has the encoder output signals, match them up to the Acorn encoder input signals.
Be sure to use a shieleded twisted pair cable and solder the drain wire to to the DB9 shell on the Acorn side.

Hey Marty,
Yes,I had looked in the DYN4 manual initially. I saw the 5v supply wire from Acorn and said " what to do with this ? ". "Just don't use it" is the answer, but I had already posted the question.

A suggestion for a video for you ( yes, asking for yet more public service, as though you don't do enough for the Acorn DIY community already ! haha . ) Since it seems you don't have some of the issues others have with Dyn4 drives ( *at lower feed/jog rates) , perhaps its a fundamental thing you are doing well compared to others, such as your method for grounding and shielding ? [edit: It could also be that the issues aren't appearing at lower speeds for some while others are needing to push the limits ] Regardless, If you did a video on grounding and shielding fundamentals alone, it might solve a lot of issues that plague people like me that aren't electrical engineers. On that vein, are you creating a ground jumper to the DYN4's DB9 (JP5) and/or DB25 (JP4) on your installs ?

Best Regards,

Jake

[martyscncgarage]

Correct, do not connect the 5V from Acorn. That POWERS an encoder. The DYN4 drive does not need this, do not connect it.

I do not put jumpers from DYN4 chassis ground to DB shells.

I have one common point for line earth ground and all grounds and shields come to it.
For example:
(What is not shown in the picture yet is the earth ground from the line cable feeding the control. It too will bolt to this stud)

[cut2cut]

Thanks Marty,

I was able to test my Dyn4 drives using the "Ruppe" method and all seems to be good at 120 ipm. I shot a quick video just for fun ( 80ipm ). ( I'm still finishing the rewiring, so forgive the messy electronics cabinet )

Thanks for the details about grounding. One more question. Do you always connect the shields on both ends or just one end ?

https://youtu.be/-Wr-AeCwG9E

Jake

[martyscncgarage]

I generally only ground the shield drain wire on one end and that's at the common ground point in the control cabinet.

Exception is for VFD cable between the VFD and the motor, where the braided shield is grounded at the VFD and the motor. I do use VFD cable between VFDs and motors and can be purchased from Automationdirect.com There was a technical paper on this subject by Belden and a fellow local Metalworking club member Rick Sparber tested and validated to work


Marty