842e encoders

[whuff]

Hello, I am working on a project that is converting a 4-20mA device to an absolute encoder. The device is measuring a jack screw that lifts a table up and down. The 4-20 a electronic yo-yo that did not hold up. The encoder is mount right to the worm drive. Right now I get 0.00833" of linear travel per turn. The encoders we are using are the A-B 842e to controllogix L-63 firmware 19.0. I have communication. Where I am getting in trouble is converting the position data to linear data. We set the table position to 1" and move it up. I want to take the encoder data and translate it to start at the 1" and go negative as the position number gets smaller and display this data on the screen. I have down scaling before but having a hard time getting this one to convert. Any advice would be appreciated. Thank you.

 

[widelto]

How is your encoder connected to your plc ??

 

[whuff]

The are ethernet based. You have to use AOP.

 

[widelto]

I have never used ethernet encoders, but you can try to set up a motion axis and configure your linear displacement based on encoder data. I have never done it, all my experience is based on motion modules with incremental encoder hardwired to the modules.

 

[whuff]

That is my usually way to do this too. I am trying to wrap my head around converting counts to a linear scale through a revolving device and the brain is just not working. Thanks for the advice.

 

[widelto]

Whuff:

Maybe this page will help you:
http://ab.rockwellautomation.com/mo...-motion-on-ethernet-ip-absolute-encoder#/tab5

Page 35 of this manual explain what I told you:
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/842e-um002_-en-p.pdf

 

[whuff]

Maybe this page will help you:
http://ab.rockwellautomation.com/mo...-motion-on-ethernet-ip-absolute-encoder#/tab5

Started there. Their example got me as far as setting the encoders up. Using 512 revs and 10,000 counts per rev. Probable overkill. Right now i get position 2258694 for 1" and 1503200 for -0.630". Take the delta and multiply by 0.00833 and you get -0.630". What I can get is turning the 2258594 into the 1" and scaled in between.

 

[whuff]

btw..I have the 842e-M model. A little different from the CM.

 

[widelto]

Have you try SCP instruction ??

 

[whuff]

Tried the motion group. Will not work with my model. I do not have a scp instruction in 5000 (only have standard)

 

[widelto]

But you can download SCP instruction as an AOI.