Need advice on how to use incremental encoders.

i have an application that has AB 845H incremental encoders connected to VFDs (Powerflex 70ECs). i can get the "raw encoder feedback data" to my plc program. i have a "home" proximity switch that is coming back to my plc. i am wondering how to deal with the fact that the drive will not have indication that home has been reached?

in other words, do i just stop the drive when i get the home prox input and then zero another variable that represents the encoder feedback? i need to have a consistent starting point in terms of encoder counts so that i will know how far a linear shaft has moved from home once the motor starts again.

thanks!

Yes, if inertion of system is small, this means that system stops immediatelly when prox is reached. If inertion is problem you must put two proxes. One will indicating parking mode of the system (variable=0), another one will serve as enable/disable increment for the variable.

I would have two speeds when you are referencing the drive slow speed until the prox is made then stop... if it is precise then 3 speeds, example:

Normal run speed @ 2500 rpm

Reference is needed speed CW at 800 until prox is made

If "Precise reference" is needed then CCW @ 300 until prox is not made

Now zero your counter

Just don’t forget the overtravel SW’s

When homing servos you can go to a prox then look for the marker (Z) channel of the encoder. This will be more accurate than a prox alone. In some cases I have disabled a limit switch and used it for a home. This may be overkill for what you are doing but it may give you some other ideas.