HEDS-970x, HEDS-972x Series
Digital Output Small Optical Encoder Modules
Data Sheet
Description
The HEDS-9700 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 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-9700 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.
Features
x
Small Size
x
Low Cost
x
Multiple Mounting Options
x
Wide Resolution Range
x
Linear and Rotary Options Available
x
x
x
x
x
x
x
No Signal Adjustment Required
Insensitive to Radial and Axial Play
-40°C to +85°C Operating Temperature
Two Channel Quadrature Output
TTL Compatible
Single 5V Supply
Wave Solderable
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.
Applications
The HEDS-9700 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 recom-
mended 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-9700 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
RESISTOR
LENS
PHOTO-
DIODES
LED
COMPARATORS
A
+
A -
B
+
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
VCC
waveforms.
3
B -
SIGNAL
PROCESSING
CIRCUITRY
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 interrup-
CHANNEL A
tions are arranged in a pattern that corresponds to the
2
radius and count density of the codewheel/codestrip.
These detectors are also spaced such that a light period
CHANNEL B
on one pair of detectors corresponds to a dark period on
the adjacent pair of detectors. The photodiode outputs
4
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
GND
phasing technique, the digital output of channel A is in
quadrature with channel B (90 degrees out of phase).
1
EMITTER SECTION
CODE
WHEEL
DETECTOR SECTION
2
Output Waveforms
C
P
Pulse Width (P): The number of electrical degrees that
an output is high during one cycle. This value is nomi-
nally 180°e or 1/2 cycle.
Pulse Width Error ('P): The deviation, in electrical de-
CHANNEL A
grees, of the pulse width from its ideal value of 180°e.
ф
AMPLITUDE
S1
S2
S3
S4
CHANNEL B
State Width (S): The number of electrical degrees be-
tween 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 de-
grees, of each state width from its ideal value of 90°e.
ROTATION
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
Phase (I): 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 ('I): 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 mod-
ule (so the marking is visible), channel A will lead chan-
nel 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.
-40
-40
-0.5
-0.5
-1.0
Max.
85
85
7
V
CC
5
260
Units
°C
°C
V
V
mA
°C
t ≤5 sec.
Notes
See Note
See Note
3
Recommended Operating Conditions
Parameter
Temperature
Supply Voltage
Load Capacitance
Count Frequency
Symbol
7
V
CC
C
L
Min.
4.5
Max.
5.5
100
20
Units
°C
V
pF
kHz
Ripple < 100 mV
p-p
3.2 k: pull-up
(Velocity (rpm) x N)/60
Notes
Note:
The module performance is guaranteed to 20 kHz but can operate at higher frequencies. For operation at 30KHz for resolution options E, F,
G and H, the maximum pulse width and logic state width errors are 40°e and phase error is 15°e.
Encoding Characteristics
Encoding Characteristics over Recommended Operating Range and Recommended Mounting Tolerances. These
characteristics do not include codewheel/codestrip contributions.
Case 1
Case 2
Parameter
Symbol
Typ.
Max.
Max.
Units
Notes
Pulse Width Error
Logic State Width Error
Phase Error
'P
'S
'I
7
5
2
30
30
10
40
40
15
°e
°e
°e
Case 1: Module mounted on tolerances of ±0.13 mm (0.005”). Case 2: Module mounted on tolerances of ±0.25 mm
(0.010”)
Note:
See Figures in Mounting Considerations for details on Case 1 and Case 2 mounting tolerances.
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
200
50
2.4
0.4
Min.
Typ.
17
Max.
40
Units
mA
V
V
ns
ns
I
OH
= -40 μA
I
OL
= 3.2 mA
C
L
= 25 pF, R
L
= 11 k:
C
L
= 25 pF, R
L
= 11 k:
Notes
4
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
mm
(inch)
mm
(inch)
mm
(inch)
mm
(inch)
Notes
Includes eccen–
tricity errors
1.04
(0.041)
0.76
(0.030)
3.60
(0.142)
mm
(inch)
Optional Packages Available
Mounting Option #51 – Rounded Outline (Baseplane Mounting)
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