Beckhoff EK110x/EK15xx Coupling Guide

Beckhoff EK110x/EK15xx EtherCAT Coupling Complete Guide

Overview of Product Positioning and Selection

In the Beckhoff EtherCAT terminal system, the coupler plays a central role in connecting the upper layer EtherCAT network with the local EL/ES series terminals. It converts the physical layer of Ethernet 100BASE-TX, 100BASE-FX, or POF (polymer fiber) into internal E-bus signals and is responsible for providing 5V communication power to the terminal chain. Different application scenarios - from standard copper cables, anti-interference optical fibers to low-cost plastic optical fibers, from fixed topologies to flexible production lines supporting hot connect - correspond to different types of couplers.

This article is aimed at automation system integration and on-site maintenance engineers, and provides a systematic review EK1100、EK1101、EK1101‑0010、EK1101‑0080、EK1100‑0008、EK1101‑0008、EK1501、EK1501‑0010  The technical differences, installation and wiring specifications, LED diagnosis, fiber power budget calculation, passive terminal placement rules, and explosion-proof (ATEX/IECEx/cFMus) special conditions of the nine EtherCAT couplers and EK1541. Whether you are replacing an old Woodward controller or planning an EtherCAT network for a new production line, this article can provide practical references.

Comparison and selection points of coupler models

2.1 Copper Cable RJ45 Interface Series

Model features, upper layer distance, special functions

EK1100 standard coupler, no ID switch ≤ 100m basic type, does not support Hot Connect

EK1101 with 3-digit hexadecimal ID switch (0-4095) ≤ 100m supports Hot Connect and can dynamically identify replaceable I/O groups

EK1101‑0010 Extended Distance， Support 4-wire system ≤ 300 m (both ends are Extended devices) to break through the 100 m limit of copper cables, suitable for cross workshop connections

EK1101-0080 Fast Hot Connect (FHC) ≤ 100m connection time<1 second, used for fast tool changing or modular production lines

All RJ45 type couplers provide two 100BASE-TX ports (X1 IN/X2 OUT), support auto crossing, and can use direct or crossover Ethernet cables. The maximum power supply capacity of the E-bus is 2 A (-25...+55 ℃), and if it exceeds this, it needs to be plugged into the EL9410 or other power supply input terminals.

2.2 M8 Circular Connector Series

Model Features Applicable Scenarios

EK1100-0008 standard coupler, M8 interface requires a more compact and seismic resistant connection, commonly used in vibration environments

EK1101-0008 with ID switch, M8 interface is the same as EK1101, but equipped with M8 connector

It is recommended to use ZK1090-3131 xxxx cable for M8 interface, with a tightening torque of 0.4 Nm (maximum 0.5 Nm).

2.3 Fiber Optic and POF Series

Characteristics of Maximum Distance for Model Media

EK1501 multimode fiber (50/125 or 62.5/125 μ m) 2 km anti electromagnetic interference, suitable for cross plant or harsh environments

EK1501-0010 single-mode fiber (9/125 μ m) for an ultra long distance of 20 km, needs to be used in conjunction with EK1521-0010

EK1541 POF (polymer fiber, 1 mm core diameter) can be quickly assembled on site at 50 m, with low cost and large bending radius

All fiber couplers support ID switches and Hot Connect (except for EK1100), and are equipped with built-in 1300 nm (EK1501/-0010) or 650 nm (EK1541) lasers (Class 1).

Mechanical installation and power wiring specifications

3.1 DIN rail installation

All EK11xx/EK15xx have a width of 44 mm (RJ45/M8 type) or 49 mm (fiber/POF type) and a height of 100 mm.

Install on a 35 mm guide rail (EN 60715), steps: first hang the guide rail and press it tightly until the lock buckle "clicks" into engagement.

Enhance mechanical load capacity: If there is strong vibration (5g acceleration) on site, TH35-15 guide rails should be used, with mechanical fasteners (such as grounding terminals) clamped at both ends. The total number of terminals should not exceed 64 (12mm width) or 32 (24mm width), and the distance between guide rail fixing points should be ≤ 5cm.

When disassembling, pull the orange buckle strap about 1 cm to release the buckle, and then pull out the terminal.

3.2 Power wiring and potential group

Us (system power supply): The upper spring terminals "24V" and "0V" provide power to the coupler electronic circuit and E-bus. The voltage range is 24V DC ± 20% (19.2-28.8V).

Up (power contacts): The lower three pairs of spring terminals (+/-/±) are used to provide on-site power (24V, maximum 10A) to the bus terminals and are electrically isolated from Us.

The maximum current of the E-bus is 2A, and if it exceeds the limit, EL9410 (power supply input terminal) needs to be inserted. TwinCAT System Manager will automatically calculate the total current of E-bus, and when it is negative, it will prompt the need for power supply.

Fuse: We recommend 1   A slow melting (depending on the load adjustment), Up maximum 10   A slow melting.

Electrical isolation: The withstand voltage between Us and Up is 500   V, and the PE power supply contact is capacitively coupled to the guide rail.

3.3 Special placement rules for passive terminals

Passive terminals do not participate in active data exchange and do not consume E-bus current (such as EL9195). To ensure the integrity of the E-bus signal, it is not allowed to connect more than two passive terminals in series, and the passive terminals cannot be directly attached to the coupler for installation (at least one active terminal should be placed after the coupler). Incorrect placement can lead to unstable E-bus communication and even frame loss.

EtherCAT Communication Fundamentals and Port Allocation

4.1 Data Flow (Taking EK1100 as an Example)

EK1100 integrates EtherCAT Slave Controller (ESC) internally, with a total of 3 valid ports:

Port 0 (A): Physical input (X1 IN)

Port 1 (B): Internal E-bus output (connected to the right terminal chain)

Port 2 (C): Physical output (X2 OUT)

Processing sequence: frames enter from X1 IN → port 0 is sent to ESC for processing → data updates enter the terminal chain from port 1 → frames returned by the terminal chain return from port 1 to ESC → then leave from port 2 to the next device → finally return to the main station from X1 IN. Port 3 (D) is not in use and is considered closed.

4.2 EtherCAT State Machine (ESM)

Status abbreviation function

Init - No communication, initialize synchronization manager

Pre Operational Pre OP email communication available, no process data available

Safe Operational Safe OP: The input data is valid, and the output remains in a safe state

Operational OP normal input/output

Boot - Only used for FoE firmware updates

The corresponding states of the RUN LED of the coupler are: off=Init, flashing=Pre OP, single flash=Safe OP, constant light=OP, fast flashing=Bootstrap.

4.3 Distributed Clock (DC) Support

Partial couplers (EK1100 from firmware 06, EK1101 from firmware 01, EK1501 from firmware 01, etc.) support as DC reference clocks. It is necessary to manually select "Cyclic Mode Enable" and "Use as potential Reference Clock" in TwinCAT. If it is forcibly enabled without support, it will cause communication abnormalities.

Hot Connect and Fast Hot Connect (FHC)

5.1 Standard Hot Connect (EK1101, EK1501, EK1541)

Assign unique IDs to couplers and their subordinate terminal groups through a three digit hexadecimal dip switch (0-4095). EtherCAT master stations (such as TwinCAT) can dynamically add or remove this group during operation, achieving flexible production lines or interchangeable workstations. When configuring, the Group ID needs to be specified in System Manager.

5.2 Fast Hot Connect（EK1101‑0080）

Specially designed for tool quick change or modular robot workstations, with a connection recovery time of less than 1 second (standard Hot Connect takes several seconds). Mandatory requirement:

FHC ports can only connect to FHC ports (marked with special icons) and cannot connect to standard EtherCAT devices.

If misconnected, TwinCAT ADS Logger will report the error "invalid hot connect group" and require a power outage and restart.

Distributed clock (DC) cannot be used, otherwise it will prolong the synchronization time and lose the FHC advantage. Confirm that 'DC in use' is not selected in the Master settings.

The FHC group configuration method is the same as the standard Hot Connect, but the system will automatically recognize the FHC port (marked in red in TwinCAT).

Diagnostic LED Quick Check Table

All EK couplers have the following LEDs (see manual figures 60-62 for specific locations):

Meaning of LED color

Us green light: 24V power supply is normal

Up green light: Power contact 24V is normal

RUN green refers to the ESM status mentioned earlier

Link/ACT (X1 IN) green off: no connection; Always on: Connected; Flashing: Data transmission and reception

Link/ACT (X2 OUT) green as above, pointing to downstream devices

Link/ACT E-bus green out: no terminal or E-bus disconnection; Always on: Connected terminals; Flashing: in communication

Troubleshooting ideas for abnormal RUN or E-bus LED:

Us does not light up → Check the 24V input and fuse.

RUN keeps flashing (Pre OP) → The main station has not configured process data correctly or has not sent OP instructions.

E-bus LINK off → poor terminal contact or end not connected to EL9011 terminal cover plate.

Fiber coupler LINK/ACT does not light up → Check if the fiber is reversed (Tx → Rx), use a mobile phone camera to observe infrared light (EK1501 is 1300   nm invisible and requires an infrared detector; EK1541 is visible red light at 650nm.

Deep application of fiber optic and POF couplers

7.1 Optical Power Budget and Attenuation Calculation (Example EK1501/EK1521)

Taking EK1501 (multimode) and EK1521 with a distance of 2.1 km and using 50/125 μ m fiber as an example:

Minimum transmission power: -23.5 dBm

Receiver sensitivity: -31 dBm

Power budget=(-23.5) - (-31)=7.5 dB

Source of attenuation:

Fiber loss: 0.8 dB/km × 2.1 km=1.68 dB

SC connectors (2 pieces): 0.25   dB × 2=0.5   dB

Fusion point (3 pieces): 0.3   dB × 3=0.9   dB

Total attenuation=3.08 dB

Power margin=7.5-3.08=4.42 dB (>3 dB, safe)

Attention: EK1501-0010 (single-mode) will have an increased transmission power of -5 dBm, sensitivity of -35 dBm, and a power budget of 30 dB starting from 2023. It can cover a distance of 20 km.

7.2 POF coupler EK1541 and on-site assembly

EK1541 uses Versatile Link duplex connectors with a maximum distance of 50 meters. On site assembly steps (using ZS1090-0008 kit):

Peel off the outer layer of the POF wire by about 7mm, exposing the core wire (with a diameter of 1mm).

Insert two optical fibers into the duplex connector separately, paying attention to the Tx → Rx crossover (when the "nose" on the connector is facing up, send left and receive right? In practice, ensure that the optical channels are crossed according to Figure 56 in the manual).

Close the connector until it is securely fastened.

Use sandpaper (600 grit) and polishing pads to polish in an "8-shaped" shape, making the end face flat and smooth.

Insert the coupler socket and lock it with a click sound. Press and release the buckle during disassembly, do not pull or tug on the cable.

Blind plug: Unused fiber optic ports must be plugged into blind plugs to prevent dust and laser glare (although Class 1 lasers are safe, long-term direct viewing may still cause discomfort).

Special conditions for explosion-proof environment (ATEX/IECEx/cFMus)

Many EK couplers (such as EK1100, EK1101, EK1501) have obtained explosion-proof certification, but the following restrictions must be followed when used in Zone 2 or Class I Division 2:

The device must be installed in a casing with an IP54 rating or higher (dustproof and waterproof).

Pollution level ≤ 2 (IEC 60664-1).

Transient overvoltage shall not exceed 140% of the rated voltage (e.g. for a 24V system, transient ≤ 119 V).

Live plugging and unplugging are prohibited: terminals must be disconnected or connected, and ID switches must be adjusted only in a power-off or non explosive environment.

When the temperature at the cable inlet exceeds 70 ° C or the branch point exceeds 80 ° C, a temperature resistant cable should be selected.

When using the device modification CX2900-0107 (USB/RJ45 fixed bracket suitable for explosion-proof areas), the connector must be tied to prevent loosening.

Audio interfaces (such as N020) are not allowed to be used in explosion-proof areas.

Example of certification mark: II 3 G Ex nA IIC T4 Gc (gas) or II 3 D Ex tc IIIC T135 ° C Dc (dust). Please refer to the nameplate on the side of the product for details.

Firmware updates and ESI management (important considerations)

Although EK couplers usually do not have user upgradable firmware, when the EL/ES terminals they are connected to require firmware or FPGA updates, the following specifications must be followed to avoid damage:

Only use TwinCAT 3 (Config/FreeRun mode, no license required) and do not use third-party EtherCAT configuration tools.

Backup calibration data before updating: Some terminals (such as analog) have factory calibration parameters in their EEPROM, which will be overwritten and irrecoverable when updating ESI.

Update process:

Switch TwinCAT to Config/FreeRun with a cycle of 1ms.

Switch the target terminal to BOOTSTRAP state (via CoE or right-click menu).

Select the correct *. efw (controller firmware) or *. rbf (FPGA firmware) file.

Wait for the download to complete (power or internet disconnection is strictly prohibited).

Power on again (briefly disconnect) to activate the new firmware.

Simultaneously update multiple devices: Multiple terminals of the same model can be selected, and batch download can be performed in Boot loader mode.

Common troubleshooting table

Possible causes and solutions for the fault phenomenon

The Us LED does not light up. The 24V power supply is not connected or the fuse is blown. Measure the voltage of the power terminal, check the fuse, and confirm the polarity of the wiring

The Up LED is not lit but the Us power supply contacts are not connected or the load is short circuited. Check the wiring of the lower spring terminal; Measure Up to ground voltage

RUN LED keeps flashing (Pre OP). The main station is not configuring process data correctly or has not switched states. Scan the device in TwinCAT to check if the EtherCAT state machine is blocked

The E-bus LINK/ACT terminal has poor contact, no terminal cover plate at the end, or the E-bus is overloaded. Re plug and unplug the terminal, and confirm that EL9011 is installed at the rightmost end; Check if the total E-bus current exceeds 2A

Fiber coupler LINK/ACT eliminates fiber inversion (Tx → Tx), disconnection, and excessive attenuation when switching Tx/Rx fibers; Measure whether the light intensity at the receiving end is below the sensitivity threshold using an optical power meter

The Hot Connect group cannot recognize that the ID switch is set incorrectly or the main station has not turned on the HC check ID switch (hexadecimal 0-FFF); Configure Group ID and enable Hot Connect in TwinCAT

Fast Hot Connect port error standard device mistakenly connected to FHC port, power off, connect FHC port only to FHC device (such as EK1122-0080)

Passive terminal communication abnormality. Continuously placing more than two passive terminals. Inserting an active terminal (such as EL1004) between the passive terminals

Check the PE connection for frequent system disconnections, frame loss, EMC interference, or poor grounding; Use shielded cables and single ended grounding; Install magnetic ring