HEDS-9200#L00 Avago Technologies US Inc., HEDS-9200#L00 Datasheet - Page 2

• Manufacturer Part Number: HEDS-9200#L00
• Manufacturer: Avago Technologies US Inc.

Specifications of HEDS-9200#L00

• Lead Free Status / Rohs Status: Compliant

Applications
The HEDS-9200 provides sophisti-
cated motion detection at a low
cost, making it ideal for high
volume applications. Typical
applications include printers,
plotters, tape drives, and factory
automation equipment.
Note: Avago 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.
Please contact sales representative
if more clarification is needed.
Theory of Operation
The HEDS-9200 is a C-shaped
emitter/detector module. Coupled
with a codestrip it translates linear
motion into a two-channel digital
output.
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 polycarbonate lens located
directly over the LED. Opposite the
2
Block Diagram
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
corresponds 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 then fed
through the signal processing
circuitry resulting in A, A, B and B.
Two comparators receive these
signals and produce the final out-
puts for channels A and B. Due to
this integrated phasing technique,
the digital output of channel A is in
quadrature with that of channel B
(90 degrees out of phase).
Output Waveforms
Definitions
Count density (D): The number
of bar and window pairs per unit
length of the codestrip.
Pitch: 1/D, The unit length per
count.
Electrical degree ( e): Pitch/360,
The dimension of one bar and
window pair divided by 360.
1 cycle (C): 360 electrical
degrees, 1 bar and window pair.
Pulse Width (P): The number of
electrical degrees that an output is
high during 1 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.