HEDS-973x Series
Small Optical Encoder Modules
Data Sheet
Description
The HEDS-973x series is a high performance, low cost,
optical incremental encoder module. When operated in
conjunction with either a codewheel or codestrip, this
module detects rotary or linear position. The module
consists of a lensed LED source and a detector IC enclosed
in a small C-shaped plastic package. Due to a highly colli-
mated light source and a unique photodetector array, the
module is extremely tolerant to mounting misalignment.
Features
•
Small size
•
Low cost
•
Multiple mounting options
•
Wide resolution range
•
Linear and rotary options available
•
No signal adjustment required
•
Insensitive to radial and axial play
•
- 40°C to +85°C operating temperature
•
High resolution version of the HEDS-970x
•
Two channel quadrature output
•
TTL compatible
•
Single 5 V supply
•
Wave solderable
1.8
0.071
Package Dimensions
9.8
0.386
MILLIMETERS
INCHES
LEAD THICKNESS: 0.25
0.010
DIMENSIONS ARE
CH B
V
CC
CH A
Gnd
0.50
0.020
5.5
0.217
6.40
0.252
0.14
0.006
2X Ø 2.00
0.079
03.8
0.150
(OPTICAL CENTER)
R
1.4
0.055
1.4
0.055
PIN 1 IDENTIFIER
3.0
0.118
0.8
0.031
10.8
0.425
H97X0
X 50
3.9
0.152
7.5
0.295
10.1
0.398
5.0
0.198
7.0
0.276
12.6
0.496
4.2
0.167
1.7
0.067
15.0
0.591
20.2
0.795
3.9
0.154
LEAD THICKNESS 0.25 mm
LEAD PITCH 2.54 mm
Mounting Option #50 - Standard (Baseplane Mounting)
Contact Factory for Detailed Package Dimensions
ESD WARNING:
Normal handling precautions should be taken to avoid static discharge.
The two channel digital outputs and 5 V supply input are
accessed through four solder-plated leads located on .54
mm (0.1 inch) centers.
The standard HEDS-973x is designed for use with an 11
mm optical radius codewheel, or linear codestrip. Other
options are available. Please contact factory for more in-
formation.
As seen in the block diagram, the module contains a single
Light Emitting Diode (LED) as its light source. The light is
collimated into a parallel beam by means of a single 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/codestrip moves between the emitter and
detector, causing the light beam to be interrupted by the
pattern of spaces and bars on the codewheel/codestrip.
The photodiodes which detect these interruptions are
arranged in a pattern that corresponds to the radius and
count density of the codewheel/codestrip. 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 fed through
the signal processing circuitry. Two 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 channel
B (90 degrees out of phase).
Applications
The HEDS-973x provides sophisticated motion detection
at a low cost, making closed-loop control very cost-com-
petitive! Typical applications include printers, plotters,
copiers, and office automation equipment.
Note: Avago 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.
Theory of Operation
The HEDS-973X is a C-shaped emitter/detector module.
Coupled with a codewheel, it translates rotary motion into
a two-channel digital output. Coupled with a codestrip, it
translates linear motion into a digital output.
Block Diagram
Output Waveforms
Pulse Width Error (ΔP): 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 neighbor-
ing transition in the output of channel B. There are 4 states
per cycle, each nominally 90°e.
State Width Error (ΔS): 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 (Δφ): The deviation of the phase from its ideal
value of 90°e.
Direction of Rotation: When the codewheel rotates
counterclockwise, as viewed looking down on the module
(so the marking is visible), channel A will lead channel B. If
the codewheel rotates in the opposite direction, channel
B will lead channel A.
Optical Radius (Rop): The distance from the codewheel’s
center of rotation to the optical center (O.C.) of the
encoder module.
Angular Misalignment Error (E
A
): angular misalignment
of the sensor in relation to the tangential direction. This
applies for both rotary and linear motion.
Mounting Position (R
M
): Distance from Motor Shaft center
of rotation to center of Alignment Tab receiving hole.
Definitions
Count (N) = The number of bar and window pairs or counts
per revolution (CPR) of the codewheel, or the number of
lines per inch of the codestrip (LPI).
1 Shaft Rotation = 360 mechanical degrees
= N cycles
1 cycle (c)
= 360 electrical degrees (°e)
= 1 bar and window pair
Pulse Width (P): The number of electrical degrees that an
output is high during one cycle. This value is nominally
180°e or 1/ cycle.
3
Absolute Maximum Ratings
Parameter
Storage Temperature
Operating Temperature
Supply Voltage
Output Voltage
Output Current per Channel
Soldering Temperature
Symbol
T
S
T
A
V
CC
V
O
I
O
Min.
-40
-40
-0.5
-0.5
-1.0
Max.
85
70
85
70
7
V
CC
5
60
Units
°C
°C
V
V
mA
°C
Notes
Option A & Q
All Other Options
Option A & Q
All Other Options
t ≤ 5 sec.
Recommended Operating Conditions
Parameter
Temperature
Supply Voltage
Load Capacitance
Count Frequency
Angular Misalignment
Mounting Position
E
A
R
M
-.0
0.0
R
OP
-0.14
(R
OP
-0.006)
Note: The module performance is specified at 40 kHz but can operate at higher frequencies.
Symbol
T
V
CC
C
L
Min.
-40
4.5
Typ.
Max.
85
70
Units
°C
V
pF
kHz
deg.
mm
(inch)
Notes
Option A & Q
All Other Options
Ripple < 100 mVp-p
3. kΩ pull-up
(Velocity (rpm) x N)/60
Shaft
Ø
0.13 mm (0.005")
See Mounting Considerations
5.0
5.5
100
40
+.0
Electrical Characteristics
Electrical Characteristics over Recommended Operating Range, Typical at 5°C.
Parameter
Supply Current
High Level Output Voltage
Low Level Output Voltage
Rise Time
Fall Time
Symbol
I
CC
V
OH
V
OL
t
r
t
f
Min.
Typ.
17
57
Max.
40
85
Units
mA
V
Notes
Option A & Q
All Other Options
I
OH
= -00
μA
I
OL
= 3.86 mA
C
L
= 5 pF,
R
L
= 3.3 kΩ pull-up
.4
0.4
180
40
V
ns
ns
4
Encoding Characteristics
Encoding Characteristics over Recommended Operating Condition and recommended mounting tolerances. These
characteristics do not include codewheel/codestrip contribution. The Typical Values are averages over the full rotation
of the codewheel. For operation above 40 kHz, see frequency derating curves.
Parameter
Pulse Width Error
Logic State Width Error
Phase Error
Symbol
ΔP
ΔS
Δφ
Typical
5
3
Maximum
45
45
15
Units
°e
°e
°e
Note: 3.3 kΩ pull-up resistors used on all encoder module outputs.
Frequency Derating Curves
Typical performance over extended operating range. These curves were derived using a 5 pF load with a 3.3 k pull-up
resistor. Greater load capacitances will cause more error than shown in these graphs.
A
0
CHANGE IN STATE WIDTH ERROR
(ELECTRICAL DEGREES)
+85 °C
-5
-40 °C
-10
+25 °C
CHANGE IN PULSE WIDTH ERROR
(ELECTRICAL DEGREES)
15
-40 °C
10
+25 °C
5
+85 °C
0
-5
B
-15
0
50
100
FREQUENCY (KHz)
150
200
0
50
100
FREQUENCY (KHz)
150
200
5
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