Siemens SIMATIC NET PROFIBUS OBT User manual

Contents
Introduction 1
The SIMATIC NET PROFIBUS
OBT Product 2
Functional Description 3
Network Topology 4
Installation and Startup 5
Troubleshooting 6
Technical Specifications 7
Notes on the CE Label 8
References 9
Abbreviations 1
0
Release 2
C79000-G8976-C122-03
PROFIBUS Optical Bus
Terminal (OBT)
Manual
SIMATIC NET

Index-2 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
!Danger
indicates that death, severe personal injury or substantial property damage will result if proper
precautions are not taken.
!Warning
indicates that death, severe personal injury or substantial property damage can result if proper
precautions are not taken.
!Caution
indicates that minor personal injury or property damage can result if proper precautions are not taken.
Note
draws your attention to particularly important information on the product, handling the product, or to a
particular part of the documentation.
Qualified Personnel
Only qualified personnel should be allowed to install and work on this equipment Qualified persons are
defined as persons who are authorized to commission, to ground, and to tag circuits, equipment, and sy-
stems in accordance with established safety practices and standards.
Correct Usage
Note the following:
!Warning
This device and its components may only be used for the applications described in the catalog or the
technical description, and only in connection with devices or components from other manufacturers which
have been approved or recommended by Siemens.
This product can only function correctly and safely if it is transported, stored, set up, and installed cor-
rectly, and operated and maintained as recommended.
Trademarks SIMATIC, SIMATIC HMIand SIMATIC NETare registered trademarks of SIEMENS AG.
Third parties using for their own purposes any other names in this document which refer to trademarks
might infringe upon the rights of the trademark owners.
Safety Guidelines
This manual contains notices which you should observe to ensure your own personal safety, as well as to
protect the product and connected equipment. These notices are highlighted in the manual by a warning
triangle and are marked as follows according to the level of danger:
We have checked the contents of this manual for agreement with the hard-
ware and software described. Since deviations cannot be precluded entirely,
we cannot guarantee full agreement. However, the data in this manual are
reviewed regularly and any necessary corrections included in subsequent
editions. Suggestions for improvement are welcomed.
Disclaimer of LiabilityCopyright Siemens AG 1998 All rights reserved
The reproduction, transmission or use of this document or its contents is not
permitted without express written authority. Offenders will be liable for
damages. All rights, including rights created by patent grant or registration of
a utility model or design, are reserved.
Siemens AG
Bereich Automatisierungstechnik
Geschäftsgebiet Industrie-Automatisierung
Postfach 4848, D-90327 Nürnberg SiemensAG 1998
Subject to technical change.
Siemens Aktiengesellschaft Order no. C79000-G8976-C122

i
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
Contents
1 Introduction 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 The SIMATIC NET PROFIBUS OBT Product 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Functional Description 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 Interfaces 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Optoelectric Signal Conversion and Signal Regeneration 3-1. . . . . . . . . . . . .
3.3 Automatic Transmission Rate Detection 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 Supported FO Fiber Types 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 Displays 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6 Operator Controls 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Network Topology 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1 Optical Bus 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Using Long Fiber Optic Sections 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Attaching RS-485 Segments 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Installation and Startup 5-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1 Precedure for Installation 5-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Installation 5-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 Troubleshooting 6-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7 Technical Specifications 7-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8 Notes on the CE Label 8-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9 References 9-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 Abbreviations 10-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C
ontents

Contents
ii PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
C
ontents

1-1
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
Introduction
The PROFIBUS OBT (Optical Bus Terminal) is a network component for use in
optical PROFIBUS DP fieldbus networks. It allows the attachment of a single
device without an integrated optical interface to the optical PROFIBUS DP. The
following figure illustrates a typical configuration.
1) PROFIBUS cable (terminated at both ends)
2) Plastic FO cable or PCF FO cable with two fibers
PC
Programming Device
Operator Panel
SIMATIC S7-400
with IM 467 FO
ET 200M with
FO interface DP node without
FO interface
2)
1)
2)
2)
1)
OBT OBT
ÀÀ
ÀÀ
ÀTerminating resistor activted
Figure 1-1 Example of an Optical PROFIBUS DP Configuration
1

Introduction
1-2 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
Connections
The connection between the individual nodes takes the form of an optical bus with
two-fiber plastic FO cables (plastic fiber-optic cables are also known as POF,
Polymer Optical Fiber) or PCF FO cables (PCF = Polymer Cladded Fiber,
corresponds to HCS 1) fiber-optic cable). Since fiber-optic cables are
completely insensitive to electromagnetic disturbance, no grounding concept
whatsoever is necessary. For the same reason, equipotential bonding is also not
necessary. The optoelectronic conversion provides automatic isolation so that
differences in potential as can occur in extensive systems have no effect.
1) HCSis a registered trademark of Ensign-Bickford Optics
Company and stands for “Hard Polymer Cladded Silica Fiber”.
Sensitivity
Just as fiber-optic cable is insensitive to electromagnetic noise, a fiber-optic cable
emits no electromagnetic noise into the environment. Sensitive electronic devices
close to the fiber-optic cable therefore need no additional protection or noise
suppression.
Power Supply
The OBT requires an operating power supply of 24 V direct voltage that is
connected via two terminal screws.
Operating Mode
LEDs signal the current mode and any problems in operation.
Mechanical Design
The optical bus terminal consists of a compact plastic casing which can be
installed either on a standard rail or on any flat surface.

2-1
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
The SIMATIC NET PROFIBUS OBT Product
Supplied
1 x PROFIBUS OBT
1 x order form for the PROFIBUS OBT operating instructions
Not supplied
Plastic fiber-optic cable, can be purchased by the meter
Tools for connectoring fiber-optic cables
PROFIBUS OBT operating instructions
Fiber-optic cable connectors
2

The SIMATIC NET PROFIBUS OBT Product
2-2 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03

3-1
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
Functional Description
The OBT is a repeater with 3 channels.
3.1 Interfaces
The OBT has the following interfaces for attachment to PROFIBUS DP segments:
Channel 1 (CH1) is an electrical RS-485 interface. This is implemented as a
9-pin D SUB female connector. A single PROFIBUS DP node can be connected
via this channel or a PC, PG or OP can be connected to the OBT. The
maximum permitted segment length is 100 m. The copper segment should,
however, be kept as short as possible since disturbances can be coupled into
the optical PROFIBUS DP from this segment.
Channel 2 (CH2) and channel 3 (CH3) are optical interfaces. They are designed
as duplex sockets. The end of a two-fiber plastic or PCF fiber-optic cable with
two simplex connectors is connected to each of these duplex sockets.
The OBT also has a block with three terminals for connecting the 24 V power
supply and, if necessary, a grounding conductor.
3.2 Optoelectric Signal Conversion and Signal Regeneration
The OBT converts the RS-485 level signal received at channel 1 into an optical
signal level that is then output via channel 2 and channel 3.
Signals received in channel 2 or 3 are converted to electrical signals and
output on channel 1 as an electrical signal
changed back to an optical signal and then output again on the other optical
channel.
The receive channels have no echo, in other words received signals are not sent
back on the same channel.
The OBT regenerates the signals in amplitude and time. This allows up to 126
modules to be cascaded in an optical bus. The cascading depth is limited solely by
the monitoring times of the attached devices.
The propagation delay per OBT is 6 bit times.
3

Functional Description
3-2 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
3.3 Automatic Transmission Rate Detection
The OBT supports all PROFIBUS transmission rates (12 Mbps , 6 Mbps, 3 Mbps,
1.5 Mbps, 500 Kbps and 187.5 Kbps, 93.75 Kbps, 45.45 Kbps, 19.2 Kbps, 9.6
Kbps).
The transmission rate is detected automatically. No settings are necessary.
3.4 Supported FO Fiber Types
The OBT supports the fiber types listed in the table below:
Table 3-1 Distance Covered by Fiber-optic Cable between Two Devices on the Optical
PROFIBUS DP
Fiber Type Distance Between Two Devices
Plastic FO 980/1000 µm with 2 fibers
and max. 200 dB/km cable attenuation
0.1 m to 50 m
PCF FO 200/230 µm with 2 fibers and
max. 10 dB/km cable attenuation
0 m to 300 m
The specified distances between the devices assume that the partner devices use
the same optical components as the OBT. This is, for example, the case with the
IM 153-2 FO, IM 467 FO and OLM 12M.
The transmission rate is independent of the type of fiber used and the cable length.
It can be up to 12 Mbps.
The following accessories are available:
Plastic FO cable (sold in meters), connectors, polishing set and tools for
connectoring plastic FO cables
The plastic fiber-optic cables are supplied with connectors. The plastic simplex
connectors can be fitted with the available tools on site.
PCF FO cable (with connectors)
PCF cables in fixed lengths are available with 4 simplex connectors already
fitted.
3.5 Displays
The OBT has 4 LEDs for displaying the various states.

Functional Description
3-3
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
L+ 24V (green)
Unlit: No power supply or internal power supply is
defective or short-circuited
Flashes: Power supply present; Transmission rate
not yet set
Lit green: Transmission rate set, power supply
O.K.
CH1, CH2 , CH3 (channel 1 to 3, yellow)
Unlit: No data being received
Lit yellow: Data being received
L + 24V
CH1
CH2
CH3
CH2 CH3
Figure 3-1 LED Displays on the Front Panel

Functional Description
3-4 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
3.6 Operator Controls
The OBT itself does not have operator controls. Care must simply be taken that
the PROFIBUS connecting cable (not supplied) attached to Channel 1 is
terminated at both ends.

4-1
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
Network Topology
4.1 Optical Bus
The OBT is operated in conjunction with other SIMATIC devices, for example the
IM 153-2 FO or IM 467 FO on the optical PROFIBUS DP in the form of an optical
bus.
Individual PROFIBUS DP nodes with an RS-485 interface are connected to
channel 1 of the OBT via a maximum 100 m long PROFIBUS cable with bus
connectors fitted at both ends. The terminating resistors on the bus connectors
must be activated. An active or passive PROFIBUS DP node can be connected.
The OBT can be included at any point in the optical bus. If it is included at the start
or end, the unused optical channel must be closed with the rubber plug supplied.
This prevents contamination of the optical elements and disturbances caused by
light entering the module.
The connection forming the optical bus is a two-fiber plastic FO cable (maximum
length 50 m) or PCF FO cable (maximum length 300 m). The fiber-optic cables
have two simplex connectors at each end.
The fiber-optic connection between two devices is established by connecting the
optical sender of one device with one fiber to the optical receiver of the other
device and the optical receiver of the one device to the optical sender of the other
device (cross-over connection).
If an OBT or a fiber-optic cable fails, the entire network becomes two subnets.
Depending on the location of the problem, individual devices may no longer be
accessible.
The OBT does not support the creation of single-fiber rings, of monitored optical
busses or redundant ring structures.
4

Network Topology
4-2 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
4.2 Using Long Fiber Optic Sections
The maximum permitted length of PCF FO cables with the OBT is 300 m. If longer
distances are required with fiber-optic cables, then other fiber-optic types such as
graded glass fibers or monomode fibers are necessary and these can be used in a
combination of OBT with OLM (Optical Link Module). The OBT is then connected
electrically to the OLM (for example OBT/CH 1 to OLM/CH 1) and the OLM is
attached to the long fiber-optic section. At the other end of the fiber-optic section,
the arrangement is reversed by another OLM/OBT pair.
PC
PG
OP
SIMATIC S7-400
with IM 467 FO
ET 200M with
FO interface
1) PROFIBUS cable (terminated at both ends)
2) Plastic FO cable or PCF FO cable with two fibers
3) FO cable for long distances
ÀTerminating resistor activted
2)
3)
1)
2)2)
1)
OBT OBT OLM/G11 OLM/G11 OBT
1)
À
À
À
À
À
À
Figure 4-1 Example of Including Long Fiber-optic Segments with OBT and OLM
The maximum permitted transmission rate and the type and maximum length of
the fiber-optic segment are determined by the OLM type.

Network Topology
4-3
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
4.3 Attaching RS-485 Segments
The OBT allows the attachment of a PROFIBUS-RS 485-segment.
1) PROFIBUS cable
(terminated at both ends)
2) PROFIBUS cable
3) PROFIBUS connector (not terminated)
4) Plastic FO or PCF FO with two fibers
ET 200M without
FO interface DP node without
FO interface SIMATIC S7-400
with IM 467 ET 200M without FO interface
ÀTerminating resistor activted
2)
2)
2)
3)
4) 4)
1) 1)
OBT OBT
OBT
ÀÀ
À
À
ÀÀ
3)
Figure 4-2 Example of Attaching RS-485 Segments

Network Topology
4-4 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03

5-1
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
Installation and Startup
Note
Use the PROFIBUS OBT only as described in this manual.
Note
Pay particular attention to all warnings and safety-related instructions.
Note
The PROFIBUS OBT must only be operated with a safety extra-low voltage
(SELV) complying with IEC 950/ EN 60 950/ VDE 0805 with a maximum of +32 V
(typically +24 V). The power source must comply with the regulations of NEC
class 2 according to the UL/CSA approval.
Note
Do not look directly into the opening of the optical transmitter diode. The emitted
light could injure your eyes.
!Danger
Never connect the PROFIBUS OBT to a power supply of 110 V - 240 V.
Note
Select the installation location so that the climatic limit values listed in the technical
specifications can be adhered to.
5

Installation and Startup
5-2 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
Note
The RS-485 channel CH1 of the PROFIBUS OBT is electrically isolated from the
24V input. This isolation is required for correct functioning and is not a safety
measure.
Note
Make sure that the PROFIBUS OBT is adequately grounded by connecting the rail
or mounting plate to local ground with low resistance and low inductance.
Note
As the RS-485 cable, use only LAN cables approved for PROFIBUS.
Note
Do not open the OBT casing.
5.1 Precedure for Installation
Installation of the PROFIBUS OBT involves the following steps:
Installing the PROFIBUS OBT
Connecting the power supply
Connecting the optical cables
Attaching the electrical RS-485 LAN cable.

Installation and Startup
5-3
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
5.2 Installation
Installing the PROFIBUS OBT
PROFIBUS OBT can be installed either on a 35 mm standard rail with a height of
15 mm in compliance with DIN EN 50 022 - 35 x 15 or directly on a level surface.
Select the installation location so that the climatic limit values listed in the
technical specifications can be adhered to.
Make sure there is enough space for connecting the bus and power supply
cables.
Install the modules only on a low-resistance and low-inductance grounded
standard rail or mounting plate. If you secure the modules on a mounting plate,
make sure that as short a cable as possible leads from the ground terminal of
the OBT to the nearest possible ground point.
Installation on a Standard rail
Fit the upper catch of the module onto the standard rail and push in the lower
part of the module as shown in Figure 5-1 until it audibly clicks into position.
The module is removed by pulling down the locking bar.
Figure 5-1 Installation of a Module on a Standard Rail

Installation and Startup
5-4 PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-03
Installation on a Mounting Plate
PROFIBUS OBTs have two holes drilled in them. This allows them to be installed
on any flat surface, for example on the mounting plate of a cubicle.
Drill two holes in the mounting plate as shown in the drill template in Figure 5-2.
Secure the modules with machine screws (for example M3 x 75 and M3 x 55).
Use a grounding conductor with at least 2.5 mm2to establish a reliable
electrical connection between the PE terminal of the module casing and the
grounded mounting plate.
CH1
SIMATIC NET
PROFIBUS
Optical
Bus Terminal
6GK1500-3AA00
1 2 3 4 5 6 7
L + 24V
CH1
CH2
CH3
CH2 CH3
PE ML+
NEC CLASS2
24VDC, 200 mA
42.5
67.3
Figure 5-2 Installing a Module on a Mounting Plate