Encoder
An encoder translates motion into electrical pulses which are fed back into the controller. The DMC-40x0 accepts
feedback from either a rotary or linear encoder. Typical encoders provide two channels in quadrature, known as
CHA and CHB. This type of encoder is known as a quadrature encoder. Quadrature encoders may be either single-
ended (CHA and CHB) or differential (CHA,CHA- and CHB,CHB-). The DMC-40x0 decodes either type into
quadrature states or four times the number of cycles. Encoders may also have a third channel (or index) for
synchronization.
The DMC-40x0 can be ordered with 120 Ohm termination resistors installed on the encoder inputs. See the
Ordering Options for the DMC-40x0 in the Appendix for more information.
The DMC-40x0 can also interface to encoders with pulse and direction signals. Refer to the “CE” command in the
command reference for details.
There is no limit on encoder line density; however, the input frequency to the controller must not exceed 5,500,000
full encoder cycles/second (22,000,000 quadrature counts/sec). For example, if the encoder line density is 10,000
cycles per inch, the maximum speed is 300 inches/second. If higher encoder frequency is required, please consult
the factory.
The standard encoder voltage level is TTL (0-5v), however, voltage levels up to 12 Volts are acceptable. (If using
differential signals, 12 Volts can be input directly to the DMC-40x0. Single-ended 12 Volt signals require a bias
voltage input to the complementary inputs).
The DMC-40x0 can accept analog feedback (+/-10v) instead of an encoder for any axis. For more information see
the command AF in the command reference.
To interface with other types of position sensors such as absolute encoders, Galil can customize the controller and
command set. Please contact Galil to talk to one of our applications engineers about your particular system
requirements.
Sinusoidal Encoders
The DMC-40x0 can be ordered with an interconnect module that supports the use of 1Vp-p sinusoidal encoders.
This interconnect module is the ICM-42100. See A7 – ICM-42100 (-I100) in the Appendix for more information.
Watch Dog Timer
The DMC-40x0 provides an internal watch dog timer which checks for proper microprocessor operation. The timer
toggles the Amplifier Enable Output (AMPEN) which can be used to switch the amplifiers off in the event of a
serious DMC-40x0 failure. The AMPEN output is normally high. During power-up and if the microprocessor
ceases to function properly, the AMPEN output will go low. The error light will also turn on at this stage. A reset is
required to restore the DMC-40x0 to normal operation. Consult the factory for a Return Materials Authorization
(RMA) Number if your DMC-40x0 is damaged.
DMC-40x0 User Manual Chapter 1 Overview • 6
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