AEDS-96EX datasheet(2/10 Pages) AVAGO

2 / 10 page

Theory of Operation

The AEDS-96EX is a C-shaped emitter/detector module.

Coupled with a codewheel/codestrip, it translates

rotary motion into a two-channel analog output.

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 analog 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 detectors corresponds to a dark period

on the adjacent pairs of detectors. The photodiode

outputs are fed through the signal processing circuitry,

which produce the final outputs for Channel A and

Channel B. Due to this integrated phasing technique,

the analog output of Channel A is in quadrature with

Channel B (90 degrees out of phase).

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 degrees = N cycles

1 cycle (c) = 360 electrical degree, equivalent to 1

bar and window pair.

Direction of Rotation: When the codewheel rotates

in the counter-clockwise 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.

Line Density: The number of window and bar pair per

unit length, express in either lines per inch (LPI) or lines

per mm (LPmm)

Optical Radius (Rop): The distance from the

codewheel’s center of rotation to the optical center

(O.C) of the encoder module.

Gap (G): The distance from surface of the encoder to

the surface of codewheel or codestrip

Mounting Position (RM): Distance from Motor Shaft

center of rotation to center of Alignment Tab receiving

hole.

Radial and Tangential Misalignment Error (ER and

Er): For rotary motion mechanical displacement in the

radial and tangential directions relative to the nominal

alignment

Angular

Misalignment

Error

(EA):

Angular

misalignment of the sensor in relation to then

tangential direction. This applies for both rotary and

linear motion.of electrical degrees that an output is

high during one cycle, nominally 180°e or 1/2 a cycle.

AEDS-96EX Series Block Diagram

CHANNEL A

CHANNEL B

VCC

GND

SIGNAL

PROCESSING

CIRCUITRY

VLED

GND

LED

LENS

PHOTO-

DIODES

PULLUP RESISTOR

2.5 K x 2

COMPARATORS

EMITTER SECTION

CODE

WHEEL

DETECTOR SECTION

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