Quick Assembly
Two and Three Channel Optical
Encoders
Technical Data
HEDM-550x/560x
HEDS-550x/554x
HEDS-560x/564x
HEDS-5500/5600 and HEDM-
5500/ 5600 are two square waves
in quadrature. The HEDS-5540
and 5640 also have a third chan-
nel index output in addition to the
two channel quadrature. This
index output is a 90 electrical
degree, high true index pulse
which is generated once for each
full rotation of the codewheel.
The HEDS series utilizes metal
codewheels, while the HEDM
series utilizes a film codewheel
allowing for resolutions to 1024
CPR. The HEDM series is nont
available with a third channel
index.
These encoders may be quickly
and easily mounted to a motor.
For larger diameter motors, the
HEDM-5600, and HEDS-5600/
5640 feature external mounting
ears.
The quadrature signals and the
index pulse are accessed through
five 0.025 inch square pins
located on 0.1 inch centers.
Standard resolutions between 96
and 1024 counts per revolution
are presently available. Consult
local Agilent sales representatives
for other resolutions.
Features
• Two Channel Quadrature
Output with Optional Index
Pulse
• Quick and Easy Assembly
• No Signal Adjustment
Required
• External Mounting Ears
Available
• Low Cost
• Resolutions Up to 1024
Counts Per Revolution
• Small Size
• -40
°
C to 100
°
C Operating
Temperature
• TTL Compatible
• Single 5 V Supply
Applications
The HEDS-5500, 5540, 5600,
5640, and the HEDM-5500, 5600
provide motion detection at a low
cost, making them ideal for high
volume applications. Typical
applications include printers,
plotters, tape drives, positioning
tables, and automatic handlers.
Note:
Agilent Technologies
encoders are not recommended
for use in safety critical
applications. Eg. ABS braking
systems, power steering, life
support systems and critical care
medical equipment. Please
contact sales representative if
more clarification is needed.
Description
The HEDS-5500/5540, HEDS-
5600/5640, and HEDM-5500/
5600 are high performance, low
cost, two and three channel
optical incremental encoders.
These encoders emphasize high
reliability, high resolution, and
easy assembly.
Each encoder contains a lensed
LED source, an integrated circuit
with detectors and output
circuitry, and a codewheel which
rotates between the emitter and
detector IC. The outputs of the
ESD WARNING: NORMAL HANDLING PRECAUTIONS SHOULD BE TAKEN TO AVOID STATIC DISCHARGE.
2
Package Dimensions
HEDS-5500/5540, HEDM-5500
*Note:
For the HEDS-5500 and HEDM-5500, Pin #2 is a No Connect. For the HEDS-5540, Pin #2 is CH. I, the index output.
HEDS-5600/5640, HEDM-5600
*Note:
For the HEDS-5600 and HEDM-5600, Pin #2 is a No Connect. For the HEDS-5640, Pin #2 is CH. I, the index output.
3
Theory of Operation
The HEDS-5500, 5540, 5600,
5640, and HEDM-5500, 5600
translate the rotary motion of a
shaft into either a two- or a three-
channel digital output.
As seen 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. These detectors are
also spaced such that a light
period on one pair of detectors
corresponds to a dark period on
the adjacent pair of detectors. The
photodiode outputs are then fed
through the signal processing
circuitry resulting in A, A, B and B
(also I and I in the HEDS-5540
and 5640). 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).
In the HEDS-5540 and 5640, the
output of the comparator for I
and I is sent to the index
processing circuitry along with
the outputs of channels A and B.
Block Diagram
The final output of channel I is an
index pulse P
O
which is generated
once for each full rotation of the
codewheel. This output P
O
is a
one state width (nominally 90
electrical degrees), high true
index pulse which is coincident
with the low states of channels A
and B.
revolution.
Pulse Width (P):
The number of
electrical degrees that an output
is high during 1 cycle. This value
is nominally 180°e or 1/2 cycle.
Pulse Width Error (
∆P):
The
deviation, in electrical degrees, of
the pulse width from its ideal
value of 180°e.
State Width (S):
The number of
electrical degrees between a
transition in the output of channel
A and the neighboring transition
in the output of channel B. There
are 4 states per cycle, each
nominally 90°e.
State Width Error (
∆S):
The
deviation, in electrical degrees, of
each state width from its ideal
value of 90°e.
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.
Phase Error (∆φ):
The deviation
of the phase from its ideal value
of 90°e.
Definitions
Count (N):
The number of bar
and window pairs or counts per
revolution (CPR) of the
codewheel.
One Cycle (C):
360 electrical
degrees (°e), 1 bar and window
pair.
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 differ-
ence between an observed shaft
angle which gives rise to one
electrical cycle, and the nominal
angular increment of 1/N of a
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
Vibration
Shaft Axial Play
Shaft Eccentricity Plus Radial Play
Velocity
Acceleration
HEDS-55XX/56XX
-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.) TIR
30,000 RPM
250,000 rad/sec
2
HEDM-550X/560X
-40°C to +70°C
-40°C to +70°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
±
0.175 mm (± 0.007 in.)
0.04 mm (0.0015 in.) TIR
30,000 RPM
250,000 rad/sec
2
Direction of Rotation:
When the
codewheel rotates in the counter-
clockwise direction (as viewed
from the encoder end of the
motor), channel A will lead
channel B. If the codewheel
rotates in the 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 1/4 cycle.
Output Waveforms
5
Recommended Operating Conditions
Parameter
Temperature HEDS Series
Temperature HEDM Series
Supply Voltage
Load Capacitance
Count Frequency
Shaft Perpendicularity
Plus Axial Play (HEDS Series)
Shaft Eccentricity Plus
Radial Play (HEDS Series)
Shaft Perpendicularity
Plus Axial Play (HEDM Series)
Shaft Eccentricity Plus
Radial Play(HEDM Series)
Symbol Min.
T
A
T
A
V
CC
C
L
f
-40
-40
4.5
5.0
Typ.
Max.
100
70
5.5
100
100
±
0.25
(± 0.010)
Units
°C
°C
Volts
pF
kHz
mm
(in.)
non-condensing atmosphere
Ripple < 100 mV
p-p
2.7 kΩ pull-up
Velocity (rpm) x N/60
6.9 mm (0.27 in.) from
mounting surface
6.9 mm (0.27 in.) from
mounting surface
6.9 mm (0.27 in.) from
mounting surface
6.9 mm (0.27 in.) from
mounting surface
Notes
0.04
mm (in.)
(0.0015)
TIR
±
0.175
(± 0.007)
mm
(in.)
0.04
mm (in.)
(0.0015)
TIR
Note:
The module performance is guaranteed to 100 kHz but can operate at higher frequencies. 2.7 kΩ pull-up resistors
required for HEDS-5540 and 5640.
Encoding Characteristics
Encoding Characteristics over Recommended Operating Range and Recommended Mounting Tolerances
unless otherwise specified. Values are for the worst error over the full rotation.
Part No.
HEDS-5500
HEDS-5600
(Two Channel)
Description
Pulse Width Error
Logic State Width Error
Phase Error
Position Error
Cycle Error
Pulse Width Error
Logic State Width Error
Phase Error
Position Error
Cycle Error
Pulse Width Error
Logic State Width Error
Phase Error
Position Error
Cycle Error
Index Pulse Width
CH. I rise after
CH. A or CH. B fall
-40°C to +100°C
Sym.
∆P
∆S
∆φ
∆Θ
∆C
∆P
∆S
∆φ
∆Θ
∆C
∆P
∆S
∆φ
∆Θ
∆C
P
O
t
2
t
2
Min.
Typ.*
7
5
2
10
3
10
10
2
10
3
5
5
2
10
3
90
100
150
Max.
45
45
20
40
5.5
45
45
15
40
7.5
35
35
15
40
5.5
125
250
1000
Units
°e
°e
°e
min. of arc
°e
°e
°e
°e
min. of arc
°e
°e
°e
°e
min. of arc
°e
°e
ns
ns
HEDM-5500
HEDM-5600
(Two Channel)
HEDS-5540
HEDS-5640
(Three
Channel)
55
-300
70
CH. I fall after
-40°C to +100°C
CH. B or CH. A rise
Note:
See Mechanical Characteristics for mounting tolerances.
*Typical values specified at V
CC
= 5.0 V and 25°C.
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