EPC Accu-Coder Model 776 | Slim Thru-Bore Incremental Encoder — 1024 CPR, 38mm Bore, Line Driver 5–28V, 0–100°C, 10-Pin MS Connector, Anti-Rotation Flex Mount — Discontinued

Overview

The Encoder Products Company Accu-Coder Model 776 is a slim-profile thru-bore incremental encoder designed to slide directly onto a motor shaft or machine shaft — no shaft modification, no coupling, and no shaft adapter required for the shaft to pass completely through the encoder body.

This configuration makes it uniquely practical for retrofit applications where a motor or shaft is already in service and adding an encoder must not interfere with the shaft's existing mechanical arrangement.

This specific configuration carries a 38mm bore diameter — sized to accept shafts in that metric dimension — paired with 1024 cycles per revolution resolution.

At 1024 CPR with the 4× quadrature edge counting that most motion controllers apply to A/B differential outputs, the encoder effectively delivers 4096 position increments per shaft revolution.

For a motor driving a ball screw with a 5mm lead, this resolution corresponds to just over 1µm linear positional increment per quadrature count — sufficient for closed-loop positioning in the majority of industrial motion control applications.

The Model 776 is built on EPC's Opto-ASIC sensing platform — Encoder Products Company was the first encoder manufacturer to deploy Application-Specific Integrated Circuit technology in optical encoder signal processing, and the resulting signal quality advantage over discrete-component designs is particularly evident in electrically noisy industrial environments.

The Opto-ASIC integrates the light source control, photodetector array, signal conditioning, and output drive into a single chip optimised for encoder signal characteristics, producing clean square wave outputs with well-defined transition edges even in the presence of switching power supply noise, motor drive harmonics, and electromagnetic interference from adjacent equipment.

The 0–100°C operating temperature range reflects this encoder's design as a high-temperature variant — capable of sustained operation in environments where motor heat, ambient industrial temperature, and limited ventilation would exceed the standard 0–70°C range of conventional encoders.

The -H designation in the part number confirms this extended temperature capability, making the 776 viable for direct motor shaft mounting on motors that run warm under sustained load.

The anti-rotation flex mount (Style A) is a flex strap or arm assembly that attaches between the encoder housing and a fixed point on the machine structure.

As the encoder body is free to rotate relative to the shaft when the flex mount is not fitted, the mount prevents the housing from spinning with the shaft while accommodating the small angular deflections and vibration that arise in normal machine operation. 

EPC was a pioneer in this flex mount approach — a design that allows the encoder to accommodate minor shaft runout and thermal expansion without the coupling stress that rigid mounts transmit to the encoder bearing.

Key Specifications

Thru-Bore Design — Installation Flexibility

The fundamental advantage of the thru-bore format is that the shaft passes completely through the encoder from one side to the other. In contrast to a blind hollow bore encoder (where the shaft enters from one end and the other end is closed), the thru-bore allows the full shaft length and any components on the shaft's far end — pulleys, couplings, fans, or other equipment — to remain in place and accessible after the encoder is installed.

The encoder simply clamps onto the shaft at a convenient location along its length.

Installation of the Model 776 is mechanically straightforward: slide the encoder over the shaft, position it at the desired axial location, tighten the clamp collar to secure it to the shaft, and attach the anti-rotation flex mount to the nearest fixed structure.

The encoder begins providing output signals as soon as power is applied and the shaft rotates — no calibration, gapping, or alignment procedure is required.

This ease of installation makes the thru-bore format particularly valuable in retrofit applications where an existing machine needs encoder feedback added to an axis that was previously unmetered, or where an existing encoder has failed and needs to be replaced without disturbing other components.

Line Driver Output and Noise Immunity

The line driver (differential RS-422) output of this configuration is the correct choice for any installation where the cable run from the encoder to the controller exceeds a metre or two, or where the cable must pass through or alongside motor power wiring.

The differential output transmits each signal (A, /A, B, /B, Z, /Z) as a complementary pair — if noise couples onto the cable, it appears equally on both the true and complement signal, and the differential receiver at the controller rejects it as common-mode interference. The net signal at the controller input is the true encoder data, free from the noise that would degrade a single-ended output under the same conditions.

The 5–28V supply range allows the encoder to operate from either standard 5V TTL/CMOS logic supplies or higher industrial supply voltages, without requiring a separate supply converter.

The output signal levels track the supply voltage within the output circuit's drive capability, meaning the encoder's output logic levels are compatible with the receiving circuit's input requirements across this supply range.

Discontinued Status — Sourcing and Replacement

EPC has discontinued the Model 776. The current EPC thru-bore encoder product line includes the Model 775 and other series that cover similar shaft size ranges with equivalent or improved specifications.

For machines where the 776 is the installed encoder and a direct dimensional replacement is required, the available options are: sourcing tested surplus 776 units from industrial electronics suppliers, verifying whether the current EPC 775 or equivalent meets the dimensional, bore size, output, and connector requirements for the specific installation (with connector adaptation if the mating connector format differs), or engaging EPC directly to confirm the recommended current-production replacement.

The 10-pin MS-style connector is a robust and widely supported circular military-style connector — mating connectors are available from multiple sources independently of EPC, which simplifies cable assembly for custom-length replacements.

FAQ

Q1: What does "1024 CPR" mean in terms of actual position increments per revolution?

CPR stands for cycles per revolution — each full cycle consists of one complete A-channel waveform period (low to high and back to low).

Most motion controllers decode both A and B channel edges using 4× (quadrature) decoding, producing 4 position count increments per cycle. At 1024 CPR with 4× decoding, the controller counts 4096 increments per shaft revolution. If the encoder is mounted on a motor connected to a 5mm pitch ball screw with a 1:1 coupling, each count corresponds to approximately 1.22µm of linear travel.

Q2: The operating temperature is rated to 100°C — can this encoder be mounted directly on a motor that runs hot?

Yes, the 100°C maximum operating temperature was specifically designed to accommodate direct motor shaft mounting in applications where the motor's end bearing area may reach elevated temperatures under continuous high-load operation.

The -H temperature designation covers sustained operation at temperatures that standard encoders cannot handle.

However, the encoder housing should not be in contact with motor surfaces that exceed 100°C — if the motor end plate temperature under worst-case loading approaches this limit, measure actual temperatures before committing to direct mounting.

Q3: What is the purpose of the anti-rotation flex mount, and what happens if the encoder is used without it?

The encoder housing must be prevented from rotating with the shaft. Without the anti-rotation mount, the housing spins freely on the shaft and the cable whips around, breaking within minutes of operation.

The flex mount fixes the housing to a stationary machine structure while allowing the small angular movements (vibration, thermal expansion, minor misalignment) that occur in normal service. 

A rigid bracket can also prevent housing rotation, but it must accommodate these small movements through its own compliance or through a flexible coupling element — a rigid connection with no compliance transmits forces to the encoder's internal bearing, reducing service life.

Q4: The part number includes a mating connector (Y suffix) — what type of connector is this?

The Y suffix indicates a mating connector is supplied with the encoder. The 10-pin MS-style connector on the Model 776 is a military-standard circular connector (similar to the MS3106A or MS3102A series).

The mating connector supplied allows the user to terminate their own cable without sourcing the connector separately. This is particularly useful for custom cable runs where a standard cable assembly length is not available.

The mating connector is wired per EPC's pin configuration diagram, which assigns the differential A/B channel pairs, Z index pair, power, and ground to specific pins.

Q5: For the discontinued 776, what current EPC model most closely matches this configuration?

EPC's Model 775 is the current production thru-bore encoder that covers similar bore sizes and application requirements.

The 775 supports metric bore sizes including 38mm, offers 1024 CPR resolution, and is available with line driver output and MS-style connectors. 

The key differences to verify before specifying the 775 as a replacement are: the exact bore diameter availability, the connector pin configuration (which may differ from the 776's assignment), the physical housing dimensions and anti-rotation mount attachment method, and whether the 100°C operating temperature is available in the equivalent 775 configuration. Contact EPC directly with the original 776 configuration details for a confirmed current-product equivalent recommendation.