acorn and dmm dyn 4 losing steps

[martyscncgarage]

So, can you summarize the problem, and exactly what you did to remedy it? (rather than a user having to scroll back through 10 pages of posts)

Marty

[fozzyber]

• THE PROBLEM: I was losing steps between acorn and the DYN4,

• How I realized the problem: I would read the position of the servo motor by the encoder. Say encoder reading 8. I would tell acorn to move the motor 100 machine units in the positive direction, then I would tell acorn to move the motor 100 machine units in the negative direction . Then I would read the encoder position, and it would read some random number say 150 encoder units . Now we can talk about steps per rev and gear numb or what ever IT DOES NOT MATTER, because if I say move right 100 machine units, then move left 100 machine units the motor should come back to the same point!
This told me the something was up. It seemed that the DYN4 was not receiving all of the steps that the acorn was sending.
this was with the standard wiring that centroid provided for the DYN 4. I ordered the DMM cables and hooked them up as per DMM instructions with little to no change.
I had a friend come over with his scope and we read the signal output of the step / pul off of the acorn screw terminals. What we saw was a a square wave signal of 24v when the motor was being commanded to move clockwise, and a square wave signal of 5v when the motor was being commanded to move counter-clockwise. This is not what I would expect to see for steps / pul. I would expect to see 24v square wave regardless of direction.
I suspect that the DYN4 was not seeing all of the steps when acorn was sending the 5v square wave signal.

• THE FIX: I installed the differential line drivers as Russ suggested ( using the DB25 signals) and as of this time ( Im still testing) all of my problems went away or at least MUCH better.
I think the signals coming out of the DB25 are more stable and constant.

Does my explanation make sense?

Jerry

[cncman172]

Jerry,
The other part of the solution was to reroute you signal cable away from the 120V AC lines coming into the servo drivers.

Russ

[fozzyber]

I think rerouting the the ac power did help, but I don't think it was the the main issue.
After rereading my post it might seem I am yelling or upset.. I am not I only use bold and caps to highlight and emphasize key points.

Jerry

[martyscncgarage]

Jerry, you erased or deleted the videos, now there are no videos in the posts you made, making it confusing for anyone reading the thread.

I wanted to go back to see what you were using to read the encoder counts/pulses. Was it DMMDRV?

We'll probably have to delete this whole thread unless the videos can be put back up.

Marty

[fozzyber]

I only edited one video link to make it display correctly... I thought.

and yes it was DMMDRV

these are the videos in order.
i think i fixed them let me know.

Issues with acorn and dynn 4
https://youtu.be/Zh_FNE53oa8
https://youtu.be/Zh_FNE53oa8

Acorn pulse signal
https://www.youtube.com/watch?v=jNdwG2EHUZE
https://youtu.be/jNdwG2EHUZE

Therwwood y axis running at 1200ipm
https://youtu.be/JB16_LMfyf4
https://www.youtube.com/watch?v=JB16_LMfyf4