Agilent AEDS-962x for 300 LPI
Ultra Small Optical Encoder Modules
Data Sheet
Features
• Very small
• Low package height
• Built-in codewheel and codestrip
guide bumps
• Wide resolution range
• For linear and rotary applications
• No signal adjustment required
• Insensitive to radial and axial play
• 0˚C to +70˚C operating temperature
Description
This is a very small, low package
height and high performance
incremental encoder module. When
operated in conjunction with either
a codewheel or codestrip, this
module detects rotary or linear
position. The encoder 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
3.3 V supply input are accessed
through four solder plated leads
located on 2.00 mm (0.1 inch)
centers. The supply input of the
LED, rated at 16 mA, is accessed
through two leads located at
2.54 mm.
It is designed for use with an
23.36 mm optical radius codewheel
or linear codestrip. Other options
are available. Please contact the
factory for more information.
Applications
The AEDS-962x provides
sophisticated motion detection,
making closed-loop control very
cost effective. 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 and critical-care medical
equipment. Please contact a sales
representative if more
clarification is needed.
Theory of Operation
The AEDS-962x 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 Figure 1, the module
contains a single Light Emitting
Diode (LED) as its light source.
• Two-channel quadrature output
• TTL 3.3 V CMOS compatible
• Wave solderable
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
ESD WARNING:
NORMAL HANDLING PRECAUTIONS SHOULD BE TAKEN TO AVOID STATIC DISCHARGE.
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
output of channel A is in
quadrature with channel B (90
degrees out of phase).
Definitions
Note: Refer to Figure 2.
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
each state width from its
ideal value of 90°e.
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 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.
Phase Error (
∆
φ):
The deviation
of the phase from its ideal value
of 90˚e.
Direction of Rotation:
When
the codewheel rotates in the
counterclockwise 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.
Optical Radius (R
OP
):
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
):
The
distance from motor shaft center
of rotation to center of alignment
tab receiving hole.
Absolute Maximum Ratings
Parameter
Storage Temperature
Operating Temperature
Supply Voltage (Detector)
Output Voltage
Output Current per Channel
Soldering Temperature
DC Forward Current (LED)
Reverse Voltage
Symbol
T
S
T
A
V
CC
V
O
I
O
I
LED
V
R
Min.
–40
0
–0.5
–0.5
–1.5
Max.
85
70
7
V
CC
10
260
50
5
Units
˚C
˚C
V
V
mA
˚C
mA
V
Notes
t
≤
5 sec.
V
F
< 1.8 V
I
R
= 100
µA
2
Recommended Operating Conditions
Parameter
Temperature
Supply Voltage (Detector)
Load Capacitance
Pullup Resistor
Count Frequency
Angular Misalignment Error
Mounting Position
DC Forward Current (LED)
@ V
CC
= 3.3 V
Symbol
T
A
V
CC
C
L
R
PULL
f
E
A
R
M
I
LED
Min.
0
2.8
Typ.
25
3.3
none
none
Max.
70
5.2
100
Units
˚C
V
pF
kΩ
kHz
deg.
mm
(inch)
Notes
Ripple < 100 mV p-p
Recommend no pullup. Device has
integrated 2.2 KΩ on outputs.
Velocity (rpm) x N/60
Mounting Considerations
*Refer to Mounting Considerations
Recommended 110
Ω
(±10%)
series resistor between 3.3 V
supply and V
LED
.
–3.0
10
0.0
R
OP
– 2.4
(R
OP
– 0.095")
16
20
40
+3.0
Electrical Characteristics
Electrical Characteristics over Recommended Operating Range, Typical at 25˚C.
Parameter
Supply Current
(Detector)
High Level Output
Voltage
Low Level Output
Voltage
Rise Time
Fall Time
LED Forward Voltage
Symbol
I
CC
V
OH
V
OL
t
r
t
f
V
F
200
50
1.52
1.54
Min.
2
2.4
Typ. @ 3.3 V
3
3
Max.
5
3.6
0.4
Units
mA
V
V
ns
ns
V
Notes
When V
OH
= 2.4 (min.)
Typical I
OH
= –0.4 mA @ 3.3 V
When V
OL
= 0.4 (min.)
Typical I
OH
= 13 mA @ 3.3 V
C
L
= 25 pF, R
L
= 11 kΩ
Note:
Refer to Figure 2 for output waveform on t
r
and t
f
.
Encoding Characteristics
Encoding Characteristics Over the Recommended Operating Conditions and Mounting Conditions.
These characteristics do not include codewheel/codestrip contribution. The typical values are averages over
the full rotation of the codewheel.
Parameter
Pulse Width Error
Logic State Width Error
Phase Error
Symbol
∆P
∆S
∆φ
Typical
4
5
4
Maximum
40
40
15
Units
˚e
˚e
˚e
Note:
Recommended no pullup. Device has integrated 2.2 kΩ pullup resistor on Channel A & Channel B outputs.
3
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