HEDT-9001#A00 Avago Technologies US Inc., HEDT-9001#A00 Datasheet - Page 3

• Manufacturer Part Number: HEDT-9001#A00
• Description: Encoders 2 Channel 500CPR
• Manufacturer: Avago Technologies US Inc.
• Type: Optical Encoderr

Specifications of HEDT-9001#A00

• Pulses Per Revolution: 2000
• Detents: No
• Motion: Rotary
• Number Of Channels: 2
• Mounting Style: Through Hole
• Index Output: Not Indexed
• Encoder Signal: Digital
• Built In Switch: No
• Operating Supply Voltage (typ): 5VDC
• Operating Temperature Min Deg. C: -40C
• Operating Temperature Max Deg. C: 125C
• Terminal Type: PC Pins
• Termination Style: Solder Pin
• Supply Voltage: 5 V
• Product: Optical
• Technology: Rotary
• Lead Free Status / RoHS Status: Compliant

Theory of Operation
The HEDT-9000 and 9100 are C-shaped emitter/detector
modules. Coupled with a codewheel, they translate the ro-
tary motion of a shaft into a two-channel digital output.
As seen in the block diagram, each 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 poly ether imide 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 product the
digital waveforms.
Block Diagram
The codewheel rotates between the emitter and detector,
causing the light beam to be interrupted by the pattern of
spaces and bars on the code wheel. The photodiodes which
detect these interruptions are arranged in a pattern that
corresponds to the radius and design of the code wheel.
These detectors are also spaced such that a light period
on one pair of detectors corre sponds 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 fi nal outputs 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).
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Defi nitions
Count (N): The number of bar and window pairs or counts
per revolution (CPR) of the codewheel.
1 Shaft Rotation = 360 mechanical degrees,
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 (ΔP): 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 chan nel 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 elec trical degrees between the
center of the high state of chan nel A and the center of
the high state of channel B. This value is nominally 90°e
for quadrature output.
Phase Error (∆φ): The deviation of the phase from its ideal
value of 90°e.
Direction of Rotation: When the codewheel rotates in the
direc tion of the arrow on top of the module, channel A will
lead channel B. If the codewheel rotates in the opposite
direction, channel B will lead channel A.
Optical Radius (R
center of rotation to the optical center (O.C.) of the en-
coder module.
Output Waveforms
1 cycle (C) = 360 electrical degrees (°e),
S1
op
): The dis tance from the codewheel’s
P
= N cycles.
= 1 bar and window pair.
ф
S2
ROTATION
C
S3
S4
CHANNEL B
CHANNEL A