Galil Motion Control DMC-21 5 Series User Manual page 12

Encoder
An encoder translates motion into electrical pulses which are fed back into the controller. The DMC-21x5 accepts
feedback from either a rotary or linear encoder. Typical encoders provide two channels in quadrature, known as
MA and MB. This type of encoder is known as a quadrature encoder. Quadrature encoders may be either single-
ended (MA and MB) or differential (MA+, MA- and MB+, MB-). The DMC-21x5 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-21x5 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
3,750,000 full encoder cycles/second (15,000,000 quadrature counts/sec). For example, if the encoder line density
is 10,000 cycles per inch, the maximum speed is 375 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-21x5. Single-ended 12 Volt signals require a bias
voltage input to the complementary inputs.
The DMC-21x5 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 about particular system requirements.
Watch Dog Timer
The DMC-21x5 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-21x5 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-21x5 to normal operation. Consult the factory for a Return Materials Authorization
(RMA) Number if the controller has been damaged.
Chapter 1 Overview ▫ 7 DMC-21x5 User Manual 1.0a1