HEDS-974X Datasheet, PDF (1/6 Pages) Agilent(Hewlett-Packard) – 180, 300, 360 LPI Small Optical Encoder Modules

HEDS-974x Series
For 180,300, 360 LPI Small Optical Encoder Modules
Data Sheet
Description
The HEDS-974x series is a high performance, low cost,
optical incremental encoder module. When operated in
conjunction with codestrip, this module detects linear
position. The module 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 5 V supply input are
accessed through four solder-plated leads located on 2.54
mm (0.1 inch) centers.
Applications
The HEDS-974x provides sophisticated motion detection
at a low cost, making close-loop control very cost-
competitive! 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, power steering, life support systems
and critical care medical equipment. Please contact sales
representative if more clarification is needed.
Theory of Operation
The HEDS-974x 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 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 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 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 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 digital
output of channel A is in quadrature with channel B
(90 degrees out of phase).
Features
• Small size
• Multiple mounting options
• Wide resolution range
• Linear options available
• No signal adjustment required
• Insensitive to radial and axial play
• –40°C to +85°C operating temperature
• High resolution version of the HEDS-970x
• Two-channel quadrature output
• TTL or 5.0 V CMOS compatible
• Single 5 V supply
• Wave solderable
• Integrated 2.5 KΩ pullup on outputs
ESD WARNING: NORMAL PRECAUTIONS SHOULD BE TAKEN TO AVOID STATIC DISCHARGE.