Features

• Small size

• Multiple mounting options

• Wide resolution range

• Linear options available

• No signal adjustment required

• Insensitive to radial and axial play

• –40

• 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 K

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

detectorsarealsospacedsuchthatalightperiodononepair

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).

ESD WARNING: NORMAL PRECAUTIONS SHOULD BE TAKEN TO AVOID STATIC DISCHARGE.

HEDS-974x Series

For 180,300, 360 LPI Small Optical Encoder Modules

Data Sheet