Delta Tau GEO BRICK LV Manuale Utente
Turbo PMAC User Manual
Setting Up Feedback and Master Position Sensors
49
SETTING UP FEEDBACK AND MASTER POSITION SENSORS
Turbo PMAC systems can interface to a wide variety of position sensors for both feedback and master
use, either on the main control boards or through a variety of accessory boards. This section summarizes
the basic hardware and software setup issues; more details can be found in the appropriate hardware
reference manuals and the Turbo PMAC Software Reference Manual.
use, either on the main control boards or through a variety of accessory boards. This section summarizes
the basic hardware and software setup issues; more details can be found in the appropriate hardware
reference manuals and the Turbo PMAC Software Reference Manual.
Note that the initial setup for feedback or master sensors is independent of any motor or coordinate
system. A motor or coordinate system may use the numerical value resulting from the initial hardware
and/or software processing of a position signal, but this is not required. It is also possible for user
programs or commands to access these position values directly, without a motor or coordinate-system
automatic function using them at all.
system. A motor or coordinate system may use the numerical value resulting from the initial hardware
and/or software processing of a position signal, but this is not required. It is also possible for user
programs or commands to access these position values directly, without a motor or coordinate-system
automatic function using them at all.
Setting Up Quadrature Encoders
Digital quadrature encoders are the most common position sensors used with Turbo PMACs. Interface
circuitry for these encoders comes standard on board-level Turbo PMAC controllers, UMAC axis-
interface boards, and QMAC control boxes.
circuitry for these encoders comes standard on board-level Turbo PMAC controllers, UMAC axis-
interface boards, and QMAC control boxes.
Signal Format
Quadrature encoders provide two digital signals that are a function of the position of the encoder, each
nominally with 50% duty cycle, and nominally one-quarter cycle apart. This format provides four distinct
states per cycle of the signal, or per line of the encoder. The phase difference of the two signals permits
the decoding electronics to discern the direction of travel, which would not be possible with a single
signal.
nominally with 50% duty cycle, and nominally one-quarter cycle apart. This format provides four distinct
states per cycle of the signal, or per line of the encoder. The phase difference of the two signals permits
the decoding electronics to discern the direction of travel, which would not be possible with a single
signal.
Typically, these signals are at 5V TTL/CMOS levels, whether single-ended or differential. The input
circuits are powered by the main 5V supply for the controller, but they can accept up to +/-12V between
the signals of each differential pair, and +/-12V between a signal and the GND voltage reference.
circuits are powered by the main 5V supply for the controller, but they can accept up to +/-12V between
the signals of each differential pair, and +/-12V between a signal and the GND voltage reference.
Differential encoder signals can enhance noise immunity by providing common-mode noise rejection.
Modern design standards virtually mandate their use for industrial systems, especially in the presence of
PWM power amplifiers, which generate a great deal of electromagnetic interference.
Modern design standards virtually mandate their use for industrial systems, especially in the presence of
PWM power amplifiers, which generate a great deal of electromagnetic interference.
Hardware Setup
This section describes Turbo PMAC encoder hardware interface in general terms. Consult the Hardware
Reference Manual for your particular configuration for details.
Reference Manual for your particular configuration for details.
Turbo PMAC’s encoder interface circuitry employs differential line receivers, but is configured at the
factory to accept either single-ended or differential encoders. In this configuration, the main (+) line is
pulled up to 5V, and the complementary (-) line is tied to 2.5V with a voltage divider. With a single-
ended encoder, the single signal line for each channel is then compared to this reference voltage as it
changes between 0 and 5V.
factory to accept either single-ended or differential encoders. In this configuration, the main (+) line is
pulled up to 5V, and the complementary (-) line is tied to 2.5V with a voltage divider. With a single-
ended encoder, the single signal line for each channel is then compared to this reference voltage as it
changes between 0 and 5V.