AEDR-8400-130 Avago Technologies US Inc., AEDR-8400-130 Datasheet - Page 2

• Manufacturer Part Number: AEDR-8400-130
• Description: 2CH, 254LPI, REF EN, 2.8V, TR
• Manufacturer: Avago Technologies US Inc.
• Series: -r

Specifications of AEDR-8400-130

• Mounting Style: SMD/SMT
• Sensing Distance: 0.017" (0.43mm)
• Sensing Method: Reflective
• Sensing Object: Codewheel/Codestrip
• Output Configuration: -
• Sensing Light: -
• Mounting Type: Surface Mount
• Current - Supply: 6mA
• Voltage - Supply: 2.6 V ~ 3 V
• Package / Case: 3.00mm L x 3.28mm W x 1.28mm H
• Features: Compact Model
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Theory of Operation
The AEDR-8400 encoder combines an emitter and a de-
tector in a single surface mount leadless package. When
used with a codewheel or linear codestrip, the encoder
translates rotary or linear motion into digital outputs.
As seen in the block diagram, the AEDR-8400 consists
of three major components: a light emitting diode (LED)
light source, a detector IC consisting photodiodes and
lens to focus light beam from the emitter as well as light
falling on the detector.
Block Diagram of AEDR-8400 Encoder
The operation of the encoder is based on the principle
of optics where the detector photodiodes sense the
absence and presence of light. In this case, the rotary/
linear motion of an object being monitored is converted
to equivalent light pattern via the use of codewheel/
codestrip. As shown in the above diagram, the reflective
area (window) of the codewheel (or codestrip) reflects
light back to the photodetector IC, whereas no light is
reflected by the non-reflective area (bar). An alternating
light and dark patterns corresponding to the window and
bar fall on the photodiodes as the codewheel rotates. The
moving light pattern is exploited by the detector circuitry
to produce digital outputs representing the rotation of
the codewheel. When the codewheel is coupled to a mo-
tor, the encoder outputs are then a direct representation
of the motor rotation. The same concept applies to the
use of a codestrip to detect linear motion.
Definitions
State Width (S): The number of electrical degrees between
a transition in Channel A and the neighboring transition
in Channel B. There are 4 states per cycle, each nominally
90°e.
2
Ch A
Ch B
V
Gnd
Gnd
V
LED
CC
Codewheel
Shaft
Note: Drawing not to scale.
Radial (E
AEDR-8400
Processing
Circuitry
Signal
R
))
Tangential (E
T
)
Codestrip or
Codewheel
Codewheel
Shaft
AEDR-8400
Angular (E
A
)
Codestrip or Codewheel
Note: Drawing not to scale
State Width Error (∆S): The deviation of state width, in elec-
trical degree, from its ideal value of 90°e.
Phase (φ): The number of electrical degrees between the
center of high state of Channel A and the center of high
state of Channel B. Nominally 90°e.
Phase Error (∆φ): The deviation of phase, in electrical de-
gree, from its ideal value of 90°e.
Pulse Width (P): The duration of high state of the output,
in electrical degree, within one cycle. Nominally 180°e
or half a cycle.
Pulse Width Error (∆P): The deviation of pulse width, in elec-
trical degree, from its ideal value of 180°e.
Count (N): The number of window and bar pair per revolu-
tion (CPR) of codewheel. For linear codestrip, defined as
the number of window and bar pair per unit length (lines
per inch [LPI] or lines per mm [LPmm]).
One Cycle (C): 360 electrical degrees (°e). Equivalent to one
window and bar pair.
One Shaft Rotation: 360 mechanical degrees. Also equiva-
lent to N counts (codewheel only).
Line Density: The number of window and bar pair per unit
length, expressed in either lines per inch (LPI) or lines
per mm (LPmm).
Optical radius (Rop): The distance between the codewheel
center and the center of the encoder dome.
Gap (G): The distance from surface of the encoder to the
surface of codewheel or codestrip.
Radial and Tangential Misalignment Error (E
tion, mechanical displacement in the radial and tangen-
tial directions relative to the nominal alignment.
Angular Misalignment Error (E
encoder relative to the tangential line.
Specular Reflectance (R
reflected by a surface. Quantified in terms of the per-
centage of incident light. A spectrometer can be used
to measure specular reflectance of a surface (contact
factory for more information).
Gap
f
): The amount of incident light
A
): Angular displacement of the
R
, E
T
): For rotary mo-