PROFISafe NEW PRODUCTS DEVELOPMENT KIT ... - Siemens

More documents

Recommendations

Info

22pin Sub-D connectors for connection to the bus. Most vendorsprovide connectors with a termination switch integratedinto the connector to facilitate setting the termination at the 2ends of an RS-485 cable segment. Connectors to be used forinstallations running at baud rates higher than 1.5Mbaud alsohave inductors built into the connector. Theseinductors help to diminish the reflections inherentlygenerated by the connection to the device.To avoid inconsistencies in wiring, adopt a standardconvention for wiring. Although there is no recommendationin the PROFIBUS standard, we recommendA-line green wire (RxD/TxD-Neg) , B-line redwire (RxD/TxD-Pos).Problems are caused when some connectors are wired usingone convention and others are wired using a different convention…theA- and B-lines can not be swapped and must bewired consistently throughout the installation.Avoid "Stub" LinesA "stub" or "spur" or "drop" line is a branch connection directlyfrom the trunk line which adds capacitance to the bus andcan cause excessive reflections (see issue October 1999).Although some spur lines can be tolerated at lower transmissionrates, the recommendation is to avoid use of spur linesaltogether. If a user resorts to the use of spur lines in installationsrunning at lower transmission rates, the system MAYfunction in a satisfactory manner UNTIL: more devices areadded, the covered distance is extended or the user decidesto operate the bus at higher transmission rates. After suchmodifications of the installation, the bus may no longer continueto function satisfactorily. Since each device attached tothe bus has some amount of drop line simply due to the connectionbetween the 9-pin Sub-D connector and the RS-485drivers in the device (see Figure 4), the recommendation isfor the user to avoid the use of spur lines altogether. Ifbranching configurations are required, repeaters or bus terminalsshould be used.Figure 4PROFIBUS standard, most devices provide a connectionfrom the 9-pin Sub-D connector metal shell to chassis groundof the device (as shown in Figure 5).Thus, multiple grounding points of the shield along a segmentcan generally be provided by grounding each device. If apotential difference occurs between grounding points, anequalization current can flow through a shield between thegrounding points. In this case, it is recommended to install a5AWG additional potential equalization line (3rd ground wire)between the grounding points. In the case that a bus segmentwould span a long distance, run through an extremely"noisy" area or run between two buildings (where one mightexpect a large potential difference between the groundplanes), it is recommended to convert to a fiber optic connectionto span such areas.Since all devices do not provide a connection between theshield (via the 9-pin Sub-D metal shell) and chassis ground, itis recommended to utilize a separate grounding schemewhen entering/exiting a cabinet enclosure containingPROFIBUS devices. As shown in Figure 6, the insulationshould be stripped back to expose the shield and groundingclamps should be used to secure the shield to the enclosure.Make sure that the cabinet metal surface is in full contact withthe shield, i.e., sand off any paint rust, etc.Figure 6Figure 5Follow Recommended Shielding, Grounding and LayoutProceduresThe cable shield should be connected to GND at both ends ofa segment. This improves EMC behavior by providing a lowimpedance return path for noise/current and reduces theemissions from the bus. Although not required by thePROFIBUS cable should be laid at least 10cm (4 in)from other cables if the other cable: carries DC or ACvoltages >60V, is a telephone cable or leads todevices in an explosive area. Figure 7 shows the recommendedinter-cable distances required for differentcategories of cables.•Category I:•Lan cables (Ethernet)•Other communication cables•Category II:•Shielded and unshielded cables for DC voltages > 60V and 25V and
•Shielded and unshielded cables for DC and AC voltages > 400 V•Category IV:•Signal cables of categories I - III at risk from direct lightning strikes, e.g.,connections between components in different buildings, etc.•Short circuit: A to B, A to shield, B to shield•Wire break, A or B•A/B swapped wires•Termination test: only 1 termination, more than 2 terminations•Distance (for segment length measurement)•Reflection testAfter completing checkout of the physical installation,one can then proceed to the configuration and startupof the network with confidence in itsphysical setup.Figure 7Check the InstallationAfter completing the wiring, it is a good idea to check thateverything has been done properly. The <strong>Siemens</strong> BT200 bustester (shown at right) can be used at this point to check thephysical wiring. The BT200 can be used to detect problemsor perform tests as follows:SIEMENSBT200An official installationguidline is available forPROFIBUS (document2.112) and can bedownloaded from thewww.profibus.com website,or contact the PIC ifyou are not a member of thePROFIBUS UserOrganization.ENDEXPERT TALK SEMINARPROFIBUS PRO Seminar23September 21st 2000November 16th 2000January 18th 2001March 15th 2001May 17th 2001These classes are given in Johnson City,TN. They last one day, are free of chargeand enrollment is through the PIC at thefollowing:Fax: 423-461-2103Email: profibus.center@sea.siemens.comPhone: 423-461-2576enrollment forms as well as agenda informationcan be downloaded on our websiteYou can obtain infromation regarding thisseminar through the PTO. ContactWendy Wolfe at 480-483-2456 or visittheir website at www.profibus.comClasses take place the last week of themonth in which they are given. Eachlasts from Tuesday through Friday morning.There is a discounted fee forPROFIBUS Trade Organizationmembers.Contact: the PTO at:Phone: 480-483-2456Email: wwolfe@goodnet.commbryant@goodnet.com
Page 1 and 2: August 2000advancing PROFIBUS knowl
Page 3 and 4: used in case of diagnostic situatio
Page 5 and 6: PROFIBUS-DPSupport For theOpen DACF
Page 7 and 8: Possibility 2: rely on an existing
Page 9 and 10: development and debugging environme
Page 11 and 12: CCESS PROFIBUS SUCCESS PROFIBUS SUC
Page 13 and 14: ESS PROFIBUS SUCCESS PROFIBUS SUCCE
Page 15 and 16: PC Solutions - PC-Based Control Ven
Page 17 and 18: understand format• Allow the user
Page 19 and 20: figure: no longer is specific progr
Page 21: to the maximum lengthrestriction.If

PROFISafe NEW PRODUCTS DEVELOPMENT KIT ... - Siemens

Create successful ePaper yourself

Delete template?

Save as template?