Features
Small size
Multiple mounting options
Wide resolution range
Linear 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 or 5.0 V CMOS compatible
Single 5 V supply
Wave solderable
Integrated 2.5 K
pullup on outputs
Description
The HEDS-974x series is a high
performance, low cost, optical
incremental encoder module. When
operated in conjunction with code-
strip, this module detects 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 photodetector array, the
module is extremely tolerant to
mounting misalignment.
The two-channel digital outputs and 5
V supply input are accessed through
four solder-plated leads located on
2.54 mm (0.1 inch) centers.
Applications
The HEDS-974x provides sophisti-
cated motion detection at a low
cost, making close-loop control
very cost-competitive! Typical
applications include printers,
plotters, copiers, and office
automation equipment.
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.
Agilent HEDS-974x Series
for 180, 300, 360 LPI Small Optical
Encoder Modules
Data Sheet
Please contact sales
representative if more
clarification is needed.
Theory of Operation
The HEDS-974x 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 digital outputs.
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 codestrip moves between the
emitter and detector, causing the
light beam to be interrupted by the
pattern of spaces and bars on the
codestrip. The photodiodes which
detect these interruptions are
arranged in a pattern that corre-
sponds to the count density of the
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 compara-
tors 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).
ESD WARNING: NORMAL PRECAUTIONS SHOULD BE TAKEN TO AVOID STATIC DISCHARGE.
2
Absolute Maximum Ratings
Parameter
Symbol
Min.
Max.
Units
Notes
Storage Temperature
T
S
40
85
C
Operating Temperature
T
A
40
85
C
Supply Voltage
V
CC
0.5
7
V
Output Voltage
V
O
0.5
V
CC
V
Output Current per Channel
I
O
1.0
5
mA
Soldering Temperature
260
C
t
5 sec.
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 (LPI) of the
codestrip.
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
transition in the output of channel
A and the neighboring transition
in the output of channel B. There
are four 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 (
): 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 (
): The deviation
of the phase from its ideal value
of 90
e.
Direction of Rotation: When
the codewheel rotates counter-
clockwise, 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 (R
OP
): The
distance from the codewheel's
center of rotation to the optical
center (OC) 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.
3
Electrical Characteristics over Recommended Operating Range, Typical at T
A
= 25C
Parameter
Symbol
Min.
Typ.
Max.
Units
Notes
Supply Current
I
CC
12
21
40
mA
High Level Output Voltage
V
OH
2.4
V
I
OH
= 200
A
Low Level Output Voltage
V
OL
0.4
V
I
OL
= 3.2 mA
Rise Time
t
r
70
ns
C
L
= 25 pF
Fall Time
t
f
45
ns
R
L
= (NO pullup)
Recommended Operating Conditions
Parameter
Symbol
Min.
Typ.
Max.
Units
Notes
Temperature
T
40
85
C
Supply Voltage
V
CC
4.5
5.0
5.5
V
Ripple < 100 mVp-p. Recommended
one bypass capacitor (1
F)
between V
CC
and GND less than
15 cm from the encoder.
Load Capacitance
C
L
100
pF
Pullup Resistor
R
L
none
Recommended no pullup. Device
has integrated 2.5 k
on outputs.
Count Frequency
40
kHz
(Velocity (rpm) x N) / 60
Angular Misalignment E
A
2.0
0
+2.0
deg.
Mounting considerations.
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.
Parameter
Symbol
Typical
Maximum
Units
Pulse Width Error
P
5
40
e
Logic State Width Error
S
3
40
e
Phase Error
2
15
e
4
Recommended Codewheel and Codestrip Characteristics
Parameter
Symbol
Min.
Max.
Units
Notes
Window/Bar Ratio
Ww/Wb
0.7
1.4
Center of Post to Inside
W1
1.04
mm
Edge of Window
(0.041)
(inch)
Center of Post to Outside
W2
0.76
mm
Edge of Window
(0.030)
(inch)
Center of Post to Inside Edge
L
3.60
mm
of Codestrip
(0.142)
(inch)
For linear motion, angular misalignment, E
A
, must be
2 degrees to achieve Encoding Characteristics.
All dimensions for mounting the module and codestrip should be measured with respect to the two mounting posts, shown above.
Mounting Considerations
Recommended Screw Size: M2.5 x 0.45 or 2-56
4.44
0.13
0.175
0.005
IMAGE SIDE OF
CODEWHEEL/CODESTRIP
Rm
EA
5
Flux RMA Water Soluble (per
MIL-F-14256D)
Process Parameters
1. Flux
2. Pre-heat 60 seconds total
Nominal preheat temp: 90
C
Min: 85
C Max: 110
C
3. Solder Pot Zone
Nominal dip in time:
2.5 - 4.5 seconds
Min: 2.5 seconds
Max: 5 seconds
PCB top side: 140 -160
C
PCB bottom side: 240 - 260
C
4. Wave Solder 255
C,
1.2 meters/minute line speed
5. Hot Water Wash
1st: 30
C 45 seconds
2nd: 70
C 90 seconds
6. Rinse
1st: 23
C 45 seconds
2nd: 23
C 45 seconds
7. Dry
1st: 80
C 105 seconds
2nd: 95
C 105 seconds
Package Dimensions
Mounting Option #50
Note:
If not specified, tolerances are xx.
0.7, xx.x
0.3, xx.xx
0.07 mm.
XXXXX
YYWW
C X
50
AGILENT
8.7
6.40
0.14
(OPTICAL CENTER)
2x
2.00 0.03
1.4
5.0
3.9
R 1.4
10.1
7.5
4.2
3.90 0.15
0.8
1.70 0.22
4.2
3.0
9.8
1.8
3.8
0.50
20.2 0.7
15.0
8.4
PART #
C = COUNTRY
OF ORIGIN
DATE CODE
12.6 0.7
7.0
OPTION CODE
PIN 1 ID
CH B
V
CC
CH A
GND
LEAD THICKNESS = 0.25 mm
LEAD PITCH = 2.54 mm
10.8 0.7
5.5 0.4
R 2.6
Ordering Information
HEDS-974 Option
Lead Bend
0 Straight Leads
1 Bend Leads
Resolution Options
Q 180 LPI, linear
2 300 LPI, linear
1 360 LPI, linear
Mounting Options
50 Standard
50
51
52
53
54
55
HEDS-9740
Q
*
2
*
1
*
HEDS-9741
Q
2
*
1
Recommended Wave Solder
Conditions
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