HEDC-55xx/HEDC-56xx
Two or Three Channel Quick Assembly Encoders
With Connector Latch
Data Sheet
Description
The HEDC-5xxx-xxx, while similar to the industry standard
HEDS-5xxx kit encoder, provides a connector latch on
the cover housing to improve connector retention. This
device is built upon the HP/Agilent/Avago HEDS-9000
series encoder module, and provides the same perfor-
mance, low cost, high reliability, high resolution, and ease
of assembly customers have come to expect.
Each encoder contains a lensed LED source, an integrated
circuit with detectors and output circuitry. A codewheel
(disk) which rotates between the emitter and detector IC
generates two square waves in quadrature. Three channel
units include an index pulse (high state) of 90°e, which is
generated once for each full rotation.
HEDC-5xxx-xxx provides resolutions from 50 to 1024 CPR,
and accommodating shaft diameters from 2 mm to 8 mm.
This kit encoder may be quickly and easily mounted to
a motor. The electrical interface is through five (single
ended) or ten (differential versions) 0.025 inch square
pins on 0.100 centers. Interface cable assemblies to meet
customer requirements are available also.
The differential (line driver) version offers enhanced per-
formance when the encoder is used in noisy environ-
ments, or when it is required to drive long cables. It uses
an industry standard RS422 compatible line driver IC, AEIC
7272, which provides differential outputs for each of the
encoder channels. Suggested line receivers are 26LS32
and 26LS33.
Features
•
Available in two or three channel encoder A, B and I
•
Latching connector design
•
Single 5 V supply
•
Resolution of up to 1024 CPR
•
TTL compatible, with single ended or differential
output.
•
Quick assembly
•
No signal adjustment required
•
Small size -40° C to 100° C operating temperature
Applications
High volume applications such as printers, plotters, tape
drives, textile machines, positioning tables and also
automatic handlers among others.
Note: Avago Technologies encoders are not recommended for use in
safety critical applications, e.g., ABS braking systems, power steering, life
support systems and critical care medical equipment. Avago’s products
and software are not specifically designed, manufactured or authorized
for sale as parts, components or assemblies for the planning, construc-
tion, maintenance or direct operation of a nuclear facility or for use in
medical devices or applications. Customers are solely responsible, and
waive all rights to make claims against Avago or its suppliers, for all
losses, damage, expense or liability in connection with such use. Please
contact your local sales representative if more clarification is needed.
Package Dimensions - HEDC-55xx / HEDC-56xx Single ended output:
Standard mounting considerations
16.59
Thru hole option:
n9.1
n11.13
(Thru)
31.05
19.05
3X
n1.98
Equally spaced on
n20.90
15.53
47.14
v n13.91
x1.14
2X
n2.87
PIN 1 MARK
1.3
13.18
Single ended output with standard mounting base plate
External ear mounting considerations
16.59
Thru hole option:
n9.1
3.43
n11.13
(Thru)
53.71
46.02
31.05
19.05
3X
n1.98
Equally spaced on
n20.90
47.14
PIN 1 MARK
v n13.91
x1.14
1.3
2X
n2.87
13.18
Single ended output with external ear mounting base plate
Package Dimensions
single
ended
width
height
length
31.05
16.59
47.14
15.53
2X
n2.87
differential/
line driver
31.05
16.59
51.76
47.14
31.05
unit
mm
mm
mm
16.59
A latching connector design is used on both versions.
Single Ended Output Signals
Note: All dimensions are in millimeters
2
51.76
31.05
Package Dimensions - HEDC-55xx / HEDC-56xx Differential output:
Standard mounting considerations
16.59
THRU HOLE OPTION:
n9.1
15.53
31.05
n11.13
(Thru)
19.05
3X
n1.98
Equally spaced on
n20.90
2X
n2.87
51.76
PIN 1 MARK
v n13.91
x1.13
0.65
17.13
Di erential output with standard mounting base plate
External ear mounting considerations
16.59
3.43
THRU HOLE OPTION:
n9.1
n11.13
(Thru)
53.71
46.02
31.05
47.14
15.53
19.05
3X
n1.98
31.05
Equally spaced on
n20.90
16.59
51.76
v n13.91
x1.13
2X
n2.87
2X
n2.87
PIN 1 MARK
0.65
Single Ended Output Signals
Note: All dimensions are in millimeters
Di erential output with external ear mounting base plate
17.13
Package Dimensions
single
ended
width
height
length
31.05
16.59
47.14
differential/
line driver
31.05
16.59
51.76
unit
mm
mm
mm
16.59
51.76
31.05
A latching connector design is used on both versions.
Di erential Output Signals
Note: All dimensions are in millimeters
3
Theory of Operation
This encoder translates rotary motion of a shaft into a two
or three-channel digital output.
As shown in the block diagram, these encoders contain
a single Light Emitting Diode (LED) as its light source.
The light is collimated into a parallel beam by means of
a single polycarbonate lens located directly over the LED.
Opposite the emitter is the integrated detector circuit.
This IC consists of multiple sets of photodetectors and
the signal processing circuitry necessary to produce the
digital waveforms.
The codewheel rotates between the emitter and detector,
causing the light beam to be interrupted by the pattern of
spaces and bars on the codewheel. The photodiodes which
detect these interruptions are arranged in a pattern that
corresponds to the radius and design of the codewheel.
The photodiode outputs are then fed through the signal
processing circuitry resulting in A, A-Bar, B and B-Bar
(also I and I-Bar for 3-channel units). Comparators receive
these signals and produce the final outputs for channels
A and B. Due to this integrated phasing technique, the
digital output of channel A is in quadrature with that of
channel B (90 degrees out of phase).
The output of the comparator for I and I-Bar is sent to
the index processing circuitry along with the outputs of
channels A and B.
The final output of channel I is an index pulse PO which
is generated once for each full rotation of the codewheel.
This output PO is a one state width (nominally 90 electri-
cal degrees), high state true pulse which is coincident with
the low states of channels A and B.
Definitions (see phase diagram)
Count (N):
The number of bar and window pairs or counts
per revolution (CPR) of the codewheel.
pair.
One Cycle (C):
360 electrical degrees (°e), 1 bar and window
One Shaft Rotation:
360 mechanical degrees, N cycles.
Position Error (∆Θ):
The normalized angular difference
between the actual shaft position and the position
indicated by the encoder cycle count.
Cycle Error (∆C):
An indication of cycle uniformity. The dif-
ference between an observed shaft angle which gives rise
to one electrical cycle, and the nominal angular increment
of 1/N of a revolution.
Pulse Width (P):
The number of electrical degrees that an
output is high during 1 cycle. This value is nominally 180°e
or ½ cycle.
of the pulse width from its ideal value of 180°e.
Pulse Width Error (∆P):
The deviation, in electrical degrees,
State Width (S):
The number of electrical degrees between
a transition in the output of channel A and the neighbour-
ing transition in the output of channel B. There are 4 states
per cycle, each nominally 90°e.
of each state width from its ideal value of 90°e.
State Width Error (∆S):
The deviation, in electrical degrees,
Phase (φ):
The number of electrical degrees between the
center of the high state of channel A and the center of the
high state of channel B. This value is nominally 90°e for
quadrature output
value of 90°e.
Block Diagram
RESISTOR
LENS
PHOTO-
DIODES
COMPARATORS
A
+
A -
LED
B
+
V
CC
4
CHANNEL A
3
CHANNEL B
5
CHANNEL I
2
INDEX
PROCESSING
CIRCUITRY
Phase Error (∆φ):
The deviation of the phase from its ideal
Index Pulse Width (P
O
):
The number of electrical degrees
that an index output is high during one full shaft rotation.
This value is nominally 90°e or ¼ cycle.
B -
I
+
I -
SIGNAL
PROCESSING
CIRCUITRY
EMITTER SECTION
CODE
WHEEL
DETECTOR SECTION
GND
1
4
Absolute Maximum Ratings
Parameter
Storage Temperature, T
S
Operating Temperature, T
A
Supply Voltage, V
CC
Output Voltage, V
O
Output Current per Channel, I
OUT
(Single ended)
Vibration
Shaft Axial Play
Shaft Eccentricity Plus Radial Play
Velocity
Acceleration
-40° C to 100° C
-40° C to 100° C
-0.5 V to 7 V
-0.5 V to V
CC
-1.0 mA to 5 mA
20 g, 5 to 1000 Hz
± 0.25 mm
(± 0.010 in)
0.1 mm
(0.004 in)
30,000 RPM
250,000 rad/sec
2
Direction of Rotation:
When the codewheel rotates in the clockwise direction (as viewed from the encoder end of the
motor), channel A will lead channel B. If the codewheel rotates in the counter-clockwise direction, channel B will lead
channel A.
Index Pulse Width (P
O
):
The number of electrical degrees that an index output is high during one full shaft rotation. This
value is nominally 90°e or ¼ cycle.
Output Waveform Phase Diagram
Clockwise Rotation – A leads B
C
2.4 V
0.4 V
S3
S4
2.4 V
0.4 V
t
2
2.4 V
0.4 V
P
0
P
φ
Amplitude
S1
S2
CH. A
t
1
CH. B
CH. I
Rotation of Code Wheel counter clockwise, viewed from the top of encoder
5
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