New PLC Guy: Auto Created Tag Help

Hi Forum,

I recently got hired to do PLC work straight from school so I have no experience with PLC tags.

I am using RSlogix5000 on my PLC to talk to a 1756-M02AE axis servo card. When I created the Axis named "Quench_North_Entry" it populated a AXIS_SERVO tag with many attributes. This controls a drive that moves a machine up and down to specified heights.

My first question is this. Do these attributes in the tag self update with information when I use motion commands such as MAJ or MAM on the axis?

Second Question.
My M02AE Is connected to a drive that has an encoder that I will wire into the encoder slots on the card. The Tag above has a .PositionFeedback and a .AbsolutePosition. After Homing the axis which one would give me the position of the drive? In respect to that I want to be able to tell i moved to 1inch above home point.

Any help would be greatly appreciated.

Darkzadow; said:

My first question is this. Do these attributes in the tag self update with information when I use motion commands such as MAJ or MAM on the axis?

Click to expand...

If you mean will the values in the tags be editable in ladder logic, the answer is yes. If parameters associated with that axis are caused to change or edited in the ladder editor while entering instructions, the offline value of those fields will change. If you do this online, I believe the same holds true.

If you meant will the tag comments appear on the ladder logic, the answer is also yes. If you meant something different, please clarify.

Darkzadow; said:

My M02AE Is connected to a drive that has an encoder that I will wire into the encoder slots on the card. The Tag above has a .PositionFeedback and a .AbsolutePosition. After Homing the axis which one would give me the position of the drive?

Click to expand...

IIRC, the axis.AbsolutePosition will be the last updated actual position of the drive. Once fully stopped (axis locked status) that number should be the actual position but it still may dither a tiny amount holding position. I believe there is a built in homing method which will do the offset move as you require, so you may want to investigate that as well, especially if you will always use that homing process on this particular machine.

Thank you for your answer OkiePC.

For the First part I mean that if I made the drive move would Quench_North_Entry.AbsolutePosition show where the drive was as I was moving it.