Advanced Micro Controls Inc. SMD23E2, User Manual

Page: 53 / 133

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53
REFERENCE 4
H
OMING AN
SMD23E2
OR
SMD24E2
Definition of Home Position
The Home Position is any position on your machine that you can sense and stop at. Once at the Home Posi-
tion, the motor position register of an SMD23E2 or SMD24E2 must be set to an appropriate value. If you use
the unit’s
CW/CCW Find Home commands, the motor position register will automatically be set to zero once
the home position is reached. The Encoder Position register will also be reset to zero if the encoder is avail-
able and enabled.
Defining a Home Position is completely optional. Some applications, such as those that use a
SMD23E2 or SMD24E2 for speed control, don’t require position data at all.
With the exception of Absolute Moves, the SMD23E2 and SMD24E2 can still perform all of its move com-
mands if the Home Position is not defined.
Position Preset
One of the ways to define the Home Position is to issue the Preset Position command over the network. On
units with integral encoders, both the motor position and the encoder position can be preset separately, and
the motor position can also be preset to the encoder position. The motor and encoder position values can be
preset anywhere in the range of –8,388,607 to +8,388,607.
When presetting the motor position to the encoder position, the programmed Steps per Turn
and Counts per Turn parameter values are used to scale the encoder position before the motor
position is set to it. For example, assume that the Encoder Counts per Turn is programmed to
4,096, and the Motor Steps per Turn is programmed to 2,000. If the encoder position is 4,096
when the preset command is issued, the motor position will be set to 2,000.
CW/CCW Find Home Commands
The other choice is to use the driver’s Find Home commands to order the SMD23E2 or SMD24E2 to find the
Home Position based on sensors brought into the unit. The CW Find Home command begins searching by
rotating the motor shaft in the clockwise direction and ends when the home sensor triggers while the
SMD23E2 or SMD24E2 is rotating in the clockwise direction
at the starting speed . The CCW Find Home
command operates in the same way but starts and ends with motion in the counter-clockwise direction.
This chapter explains the various ways of homing an SMD23E2 or SMD24E2 unit.
Inputs used to home the unit are introduced and diagrams that show how the unit
responds to a homing command are given.