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Identifiable emergency stop buttons

The new XB5RALK emergency stop buttons from Schneider Electric are identifiable.
In an industrial process, it is not always easy to detect which emergency stop button is activated.
The Harmony XB5RALK button can easily replace a classic emergency stop button (2 integrated NC contacts).



An additional wireless contact communicates, via the Zigbee protocol, the status of the button to the access point, which itself transmits the information via Modbus or Ethernet to the programmable logic controller or HMI.
This marking decreases the machine downtime, limits the wiring and the number of inputs on the PLC and allows the tracing of weak and dangerous points on the machine or in the “process”.

What services does the XB5RALK178F emergency stop provide?

The emergency stop button packaged in the XB5RALK178F reference button box is designed to provide two services:

  • Integration into a safety chain because it has two “O” opening contacts (former denomination Normally Closed: NC), these wired contacts will provide the necessary information to any safety module (Preventa modules) but also to safety controllers and PLCs, in order to comply with the machine directive.

In the case of simple installations, it is possible by wire to quickly define the origin of the AU actuated by using a different input for each safety module, but this solution quickly becomes very expensive in wiring, in most cases, the Emergency Stop buttons are to be wired in parallel or in series, the disadvantage being the difficulty in quickly determining which AU has been activated

  • Enter an order (M221, M340, M580 PLC) via zigbee wireless technology,

All XB5RALK178F reference button boxes are identified by a unique identifier and when an emergency AU on one of them is actuated, the information (identifier of the AU + pushbutton status: Open or Closed) is transmitted. immediately by radio to a single ZBRN access point.

The ZBRN access point retrieves all the information (AU identifier, AU status) and transmits them to an HMI via a classic wired Modbus or Ethernet TCP Modbus link so that the maintenance agent can discriminate which AU has been activated.

ZBRN access point

ZBRN access point

The ZBRN1 and ZBRN2 “access point” receivers transform a radio message from a zigbee transmitter into dedicated communication protocols under two references:

  • ZBRN1: Ethernet connection.
  • ZBRN2: Modbus RS-485.

Communication on the Modbus network: ZBRN2

The Modbus protocol is a master-slave protocol. It allows a master to request responses from slaves or to act on the request. The master can address individual slaves or send a broadcast message to all slaves. Slaves send back a message (a response) to requests addressed to them individually. They do not return responses to broadcast requests from the master.

Example of network connection

  1. Master PLC.
  2. Advantys OTB Modbus network interface module.
  3. ZBRN2 access point.
  4. ATV12 drive.
  5. Modbus serial line.
Communication on the Modbus network: ZBRN2

Modbus Slave and Modbus RTU function

  • Connector 2 RJ45 connectors.
  • Isolated Yes.
  • Maximum cable length 1000 m.
  • Polarization No.
  • Supported baud rates Auto / 1200/2400/4800/19200/38400/115200.
  • Even / Odd / No / Auto parity.
  • Stop bit 1 bit (even and odd), 2 bits (without parity).

Modbus communication and status indicator

Modbus communication and status indicator
  1. Power indicator light.
  2. Communication indicator.
  3. Radio signal strength indicator.
    The yellow Modbus communication LED takes on one of the following states:
  • On / flashing: a data exchange is in progress (depends on the amount of information).
  • Off: no data exchange is in progress.

Wiring the Modbus serial line
It is possible to directly connect the access point to a PLC up to a maximum distance of 20 m, as shown in the figure below:

Wiring the Modbus serial line

Communication on the Ethernet network: ZBRN1

Ethernet is a low cost technology widely used for local area networks. It allows data to be exchanged between several devices interconnected on a network.
Example of network connection

  1. Advantys OTB Ethernet network interface module.
  2. ZBRN1 access point associated with the ZBRCETH communication module.
  3. Automaton.
  4. Ethernet.
Communication on the Ethernet network: ZBRN1

Ethernet function

  • Connector: Two RJ45 connectors.
  • 10/100 MB / s driver.
  • Auto-negotiation, Half-duplex / Full duplex.
  • Type of cable Shielded.
  • Star topology.
  • Automatic polarity correction: Yes.

Ethernet communication and status indicator
Same as for ZBRN2.

Radio receiver

The access points are equipped with a radio receiver. They receive radio frames from wireless and battery-free pushbuttons.
Frequency 2.405 GHz (channel 11 IEEE 802.15.4).
Maximum distance 100 m (when the access point is in free field).

ZBRA2 external antenna
The ZBRA2 external antenna allows the access point to improve signal reception.

  1. Protective cap.
  2. Radio connector.
Radio receiver


Front of access bridges
The settings are made using the dial located on the front of the access point.

  • Rotation to navigate the menus.
  • Press the dial for less than 3 s to validate the parameters entered.
  • Double-click on the dial to return to the previous menu.

Operating modes
The access points have 3 operating modes:

  • Ready: Ready mode is the normal operating mode of the access point. When the access point is powered on, it displays the protocol (for example, SL for serial line) and the firmware version (for example, 01.00). Then, it switches to Ready mode and the power light turns on.
  • Configuration: It allows you to choose among other things the input hold time, IP setting, factory mode, input configuration, etc.
  • Diagnosis: The Diagnosis menu provides information on the various parameters of the equipment and the state of the detected error.
  • SD card menu: The SD card menu allows you to save and restore link and network settings.

Settings by PC
It is possible for the settings to use a PC with:

  • The DTM (Device Type Manager) is a standard field communication tool (FDT). It contains an FDT interface allowing it to communicate with the connected system. The DTMs are compatible with SoMachine V3.1 or later FDT containers for Modbus serial line, V4.1 SP1 or later for Modbus / TCP Ethernet, Unity Pro V5.0.
  • The ZBRCETH communication module (associated with ZBRT1) integrates an HTTP server. Web pages are stored in the communication module and can be updated by downloading files from the FTP site. The web pages are used to configure the access point in connected mode.

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