Rockwell Automation Publication 520-UM001K-EN-E - August 2021 225
Appendix E Encoder/Pulse Train Usage and Position StepLogic Application
or by manually moving the system into the home position. Then,
toggle the “Pos Redefine” input. This will set the drive to “Home” at its
current position and d388
[Units Traveled H] and d389 [Units Traveled
L] are set to zero. Alternately, the “Pos Redefine” bit in A560
[Enh
Control Word] can be toggled instead of utilizing a digital input.
2. Automatic Homing to Limit Switch–Program the following drive
parameters:
t062
, t063, t065...t068 [DigIn TermBlk xx] = 35 “Find Home”
Program one of the digital inputs to 35 “Find Home”.
t062
, t063, t065...t068 [DigIn TermBlk xx] = 34 “Home Limit”
Program one of the digital inputs to 34 “Home Limit”. Normally, the
“Home Limit” input would be wired to a proximity switch or photo-eye
and will indicate the system is in the home position.
A562
[Find Home Freq] sets the frequency the drive will use while it is
moving to the home position during the automatic homing routine.
A563
[Find Home Dir] sets the direction the drive will use while it is
moving to the home position during the automatic homing routine.
To begin the automatic homing routine, activate the “Find Home” input and
then initiate a valid start command. The drive will then ramp to the speed set
in A562
[Find Home Freq] and in the direction set in A563 [Find Home Dir]
until the digital input defined as “Home Limit” is activated. If the drive passes
this point too quickly it will then reverse direction at 1/10th A562
[Find Home
Freq] to the point where the Home Limit switch reactivates. Approximately
one second after the routine finds home the drive will stop. Alternately, the
“Find Home Freq” and/or “Home Limit” bits in A560
[Enh Control Word] can
be activated instead of utilizing a digital input. The inputs or bits should be
returned to inactive after the routine is complete.
Encoder and Position
Feedback
d376 [Speed Feedback] indicates the measured speed feedback or the
calculated speed feedback when no feedback device is selected. Parameter d376
[Speed Feedback] is the number value to the left of the decimal (whole number)
and d377
[Speed Feedback F] is the value to the right of the decimal (the portion
less than 1).
d378
[Encoder Speed] indicates the measured speed of the feedback device.
This is useful if the encoder is not used for motor speed control. However, the
encoder must be used for some purpose in order for d378 [Encoder Speed] to
indicate a value. Parameter d378 [Encoder Speed] is the number value to the
IMPORTANT
The “Pos Redefine” input or bit must be returned to inactive before
starting the position routine. Otherwise the drive will continuously
read a position of “0” (home) and the position routine will not
function correctly.
IMPORTANT
After the position is reached the drive will stop. If the Find Home is
removed before the homing is complete, the drive will begin running the
position routine without the proper home. In this case Home will not be
reset and the position will be in relation to the power up position.
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