The HEDR-8000 Series encoder provid...

The HEDR-8000 Series encoder provide two-channel medium-resolution encoding performance in a to a high degree small SO-8 plastic package. Their small size, reflective operation, and cheap cost enable customers to design them into applications that were impossible for earlier encoder in the same state [i]or[/i] condition as feedback sensing for the miniature motors used in copiers, cameras, vending machines, and card readers.

Imagine a position servo sensor thus small that it can fit almost anywhere. place it in a surface rise package and give it a price comparable to slot encoder that have a great deal of lower resolution. Such a sensor became reality with the introduction of the HP HEDR-8000 Series reflective optical surface rise encoders (Fig. 1).

[Figure 1 ILLUSTRATION OMITTED]

The HEDR-8000 Series encoder deliver HP reflective optical encoder technology in a surface soar package. They provide two-channel medium-resolution (75 and 150 lines by inch) encoding performance in a highly small SO-8 (small outline 8-pin) clear plastic package. The reflective technology of the HEDR-8000 Series encoder is inherently different from other HP encoder module which use transmissive technology with light passing by the and of a codewheel or codestrip. In the HEDR-8000 Series encoder light throw backs off the codewheel or codestrip.

HP's shaft encoder (sensors that measure the position of a rotating motor shaft) have always been based in succession optoelectronics, thus providing noncontact measurement and far greater reliability than contact potentiometers. The first HP encoder were the HEDS-5000/6000 consummate encoder packages, introduced in 1979 In 1987 HP introduced the low-cost HEDS-9100 encoder module a small optoelectronic package that must be combined with a codfished wheel or strip to function as a position sensor. A powerful feature of this encoder was that it could be assembled with a codewheel without the ne for "phasing," or adjusting the position of the encoder to bring the output signals within the desired specification. The HEDS-9100 family quickly became the position sensors of choice in the computer peripherals market. still by 1989, low-cost inkjet printers were introduced and distressed a smaller, lower-cost solution. This l to the introduction of the HEDS-9700 family of encoder which were smaller, les expensive, and ultrareliable, supported high-volume assembly, and furnished excellent performance.

The HEDR-8000 Series encoder were cause to growed because new low-end printers required a smaller, les expensive encoder Customers were redefining high-volume assembly capability to include surface mountability and infrared reflow oven solderability. The design objectives for the HEDR-8000 Series encoder plot were low cost, surface go up capability, and medium resolution.

The design was influenced from a new product introduced for front-panel applications, the HP HRPG family, which prov that reflective sensors were not simply feasible and inexpensive, but had the added advantage of stackability, that is, the codewheel or codestrip could be go uped on top of the encoder module and not "through" it, as required on the previous transmissive models. This not solitary enhances the high-volume assemblability, still also allows the encoder to be placed in space-limited applications.

The small size, reflective operation, and reasonable cost of the HEDR-8000 Series encoder enable customers to design them into applications that were difficult for earlier encoder individual such application is feedback sensing for the miniature motors used in copiers, cameras, vending machines, and card-readers.

Fig. 2 exhibit tos the evolution of HP optical encoder in splendor and size.

[Figure 2 ILLUSTRATION OMITTED]

Basic Operating Principles

The HEDR-8000 Series encoder combines an emitter and a detector in a single surface be built up SO-8 package. As shown in the blockade diagram, Fig. 3, the HEDR-8000 Series encoder have three lock opener parts: a single LED light source, a photodetector IC, and a pair of lense mold into the package. The len through the whole extent of the LED focuses light onto the codewheel, and the image of the codewheel is mirrored back through the lens to the photodetector IC.

[Figure 3 ILLUSTRATION OMITTED]

As the codewheel rotates, an alternating pattern of light and dark corresponding to the pattern forward the codewheel falls on the photodiodes. This light pattern is used to bring out internal signals A and B and their perfections A and B. These signals are f [i]or[/i] part of to the other comparators to produce the final digital output for Channels A and B

The HEDR-8000 Series encoders' performance is characterized on the quality and consistency of the couple encoding signals, Channel A and Channel B These signals have a quadrature relationship in the way that that, as the codewheel passes in single in kind direction, Channel A leads Channel B and as the codewheel passes in the other direction, Channel B leads Channel A. Fig. 4 indicates the output waveforms. Although the HEDR-8000 Series encoder match HEDS-9700 resolution, they have generally lower performance than their transmissive predecessors, in part because of smaller size and lower cost