H
Small Optical Encoder Modules
Technical Data
HEDS-973X Series
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
Description
The HEDS-9730 series is a high
performance, low cost, optical
incremental encoder module.
When operated in conjunction
Package Dimensions
Mounting Option #50 - Standard (Baseplane Mounting)
Contact Factory for Detailed Package Dimensions
ESD WARNING: NORMAL HANDLING PRECAUTIONS SHOULD BE TAKEN TO AVOID STATIC DISCHARGE.
2-30
5965-5867E
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 pack-
age. Due to a highly collimated
light source and a unique photo-
detector array, the module is
extremely tolerant to mounting
misalignment.
The two channel digital outputs
and 5V supply input are accessed
through four solder-plated leads
located on 2.54 mm (0.1 inch)
centers.
The standard HEDS-9730 is
designed for use with an 11 mm
optical radius codewheel, or
linear codestrip. Other options
are available. Please contact
factory for more information.
a low cost, making closed-loop
control very cost-competitive!
Typical applications include
printers, plotters, copiers, and
office automation equipment.
produce the digital waveforms.
The codewheel/codestrip moves
between the emitter and detector,
causing the light beam to be inter-
rupted by the pattern of spaces
and bars on the codewheel/code-
strip. The photodiodes which
detect these interruptions are
arranged in a pattern that corre-
sponds to the radius and count
density of the codewheel/code-
strip. 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 com-
parators 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).
Theory of Operation
The HEDS-9730 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.
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
Applications
The HEDS-9730 provides
sophisticated motion detection at
Block Diagram
2-31
Output Waveforms
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 electri-
cal 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.
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 1/2
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
Phase Error (∆φ): The deviation
of the phase from its ideal value
of 90°e.
Direction of Rotation: When the
codewheel rotates counterclock-
wise, 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.
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. Max. Units
-40
-40
-0.5
-0.5
-1.0
85
85
7
V
CC
5
260
°C
°C
V
V
mA
°C
t
≤
5 sec.
Notes
See Note
See Note
2-32
Recommended Operating Conditions
Parameter
Temperature
Supply Voltage
Load Capacitance
Count Frequency
Symbol
T
V
CC
C
L
Min.
-40
4.5
Max.
85
5.5
100
20
Units
°C
V
pF
kHz
Ripple < 100 mV
p-p
3.2 kΩ pull-up
(Velocity (rpm) x N)/60
Notes
Note:
The module performance is specified at 20 kHz but can operate at higher frequencies. Contact factory for more information.
Electrical Characteristics
Electrical Characteristics over Recommended Operating Range, Typical at 25°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
180
40
2.4
0.4
Min.
Typ.
17
Max.
40
Units
mA
V
V
ns
ns
I
OH
= -200
µA
I
OL
= 3.86 mA
C
L
= 25 pF,
R
L
= 3.3 kΩ pull-up
Notes
Encoding Characteristics
Encoding Characteristics over Recommended Operating Range 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 20 kHz, see frequency derating curves.
Parameter
Pulse Width Error
Logic State Width Error
Phase Error
Symbol
∆P
∆S
∆φ
Typical
5
3
2
Maximum
45
45
15
Units
°e
°e
°e
Note:
Module mounted on tolerances of
±
0.13 mm (± 0.005") radius referenced from centerline of codewheel shaft to alignment tabs.
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 25 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)
CHANGE IN PULSE WIDTH ERROR
(ELECTRICAL DEGREES)
B
15
-40 °C
10
+25 °C
5
+85 °C
0
+85 °C
-5
+25 °C
-40 °C
-10
-15
0
50
100
150
200
FREQUENCY (KHz)
-5
0
50
100
150
200
FREQUENCY (KHz)
2-33
Recommended Codewheel and Codestrip Characteristics
Parameter
Window/Bar Ratio
Window Length (Rotary)
Absolute Maximum Codewheel
Radius (Rotary)
Center of Post to Inside
Edge of Window
Center of Post to Outside
Edge of Window
Center of Post to Inside Edge
of Codestrip
Symbol
Ww/Wb
Lw
Rc
W1
W2
L
Min.
0.7
1.80
(0.071)
Max.
1.4
2.30
(0.091)
Rop + 3.40
(Rop + 0.134)
Units
Notes
mm
(inch)
mm
(inch)
mm
(inch)
mm
(inch)
Includes eccen–
tricity errors
1.04
(0.041)
0.76
(0.030)
3.60
(0.142)
mm
(inch)
Optional Packages Available
3.8
0.150
0.50
0.020
(OPTICAL
CENTER)
φ
2.8
0.110
3.0
0.118
0.8
0.031
hp
10.8
0.425
CH B
CH A
GND
V
CC
PIN 1 IDENTIFIER
5.5
0.217
YYWW
•
0.14
0.006
7.5
0.295
10.1
0.398
3.9
0.152
1.7
0.067
H97X0
6.40
0.252
X 51
7.0
0.276
12.6
0.496
4.34
0.171
4.2
0.167
2X
φ
2.00
0.079
3.9
0.154
15.0
0.591
20.2
0.795
1.8
0.071
LEAD THICKNESS:
0.25
0.010
9.8
0.386
DIMENSIONS ARE MILLIMETERS
INCHES
Mounting Option #51 – Rounded Outline (Baseplane Mounting)
2-34
