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6 • Chapter 1 Overview DMC-3425
For step motors, the amplifiers should accept step and direction signals.
Encoder
An encoder translates motion into electrical pulses that are fed back into the controller. The DMC-3425
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-,
CHB,CHB-). The DMC-3425 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-3425 can
also interface to encoders with pulse and direction signals.
There is no limit on encoder line density; however, the input frequency to the controller must not
exceed 3,000,000 full encoder cycles/second (12,000,000 quadrature counts/sec). For example, if the
encoder line density is 10000 cycles per inch, the maximum speed is 300 inches/second. If higher
encoder frequency is required, please consult the factory.
The standard voltage level is TTL (zero to five volts), however, voltage levels up to 12 Volts are
acceptable. (If using differential signals, 12 Volts can be input directly to the DMC-3425. Single-
ended 12 Volt signals require a bias voltage input to the complementary inputs.)
The DMC-3425 can accept analog feedback instead of an encoder for any axis. For more information
see description of analog feedback in the Command Reference under the AF command.
To interface with other types of position sensors such as resolvers or 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.
Watch Dog Timer
The DMC-3425 provides an internal watch dog timer which checks for proper microprocessor
operation. The timer toggles the Amplifier Enable Output (AEN), which can be used to switch the
amplifiers off in the event of a serious DMC-3425 failure. The AEN output is normally high. During
power-up and if the microprocessor ceases to function properly, the AEN output will go low. The
error light for each axis will also turn on at this stage. A reset is required to restore the DMC-3425 to
normal operation. Consult the factory for a Return Materials Authorization (RMA) number if your
DMC-3425 is damaged.