Brick Motion Controller Hardware Reference Manual
24
System Wiring
Setting up Quadrature Encoders
Digital quadrature encoders are the most common position sensors used with Geo Drives. Interface
circuitry for these encoders comes standard on board-level Turbo PMAC controllers, UMAC axis-
interface boards, Geo drives, 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.
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.
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.
Hardware Setup
The Geo Drive accepts inputs from up to eight digital encoders
and provides encoder position data to the motion processor. X1
is encoder 1 connector and X2 is encoder 2 and respectively up
to X8. The differential format provides a means of using
twisted pair wiring that allows for better noise immunity when
wired into machinery.
Geo Drives encoder interface circuitry employs differential line
receivers. The wiring diagram on the right shows an example
of how to connect the Geo drive to a quadrature encoder.
Function Pin
#
CHAn+ 1
CHAn- 9
CHBn+ 2
CHBn- 10
CHCn+ 3
CHCn- 11
ENCPWR 4
GND 12
1
2
3
4
8
9
15
14
13
10
12
11
5
6
7
CHBn+
ENCPWRn
CHCn-
CHCn+
CHBn-
CHAn+
CHAn-
Shield
GND
Encoder Decode
Value
Description
3 Clockwise
decode
I7mn0
7 Counter
clockwise
decode
m = 0 for axis 1-4 (n = 1-4) and m = 1 for axis 5 – 8 (n = 1-4)
