Profibus Provides Fast, Reliable Communications for Coal Mining
BUS OF THE MONTH: Profibus-DP
By Control Engineering Staff
Sidebar: Profibus: A Brief Overview
The automated control system for transporting coal from deep underground mining operations requires a fast, reliable communications bus. The vertical shaft at Jim Walter Resources (JWR) Brookwood, Alabama Blue Creek Mine No. 7 is 533 meters (1,750 feet) deep. At the top is a 45 meter (150 foot) tower called a 'headframe.' Within this frame, a hoist transports coal in two containers called 'trips.' As one trip is being dumped at the top, the other is loading at the bottom of the shaft. Both trips are connected to a looped steel cable. They move up and down in a back-and-forth rocking motion, or 'seesaw' fashion so that the trips continuously exchange places.
tion the trips precisely at their respective docking stations.
at all times. In this dynamic application not a lot of time is allowed for a control system to do calculations and to send messages back and forth. In fact, conventional bus systems operating at 56 kilobits/sec, cannot possibly handle such a requirement.
, it is important for the bus cycle time to be shorter than the program cycle time of the PLC. Profibus has a bus cycle time of only 6 milliseconds--well within the required range of the Simatic TI 555.
sts and leaves additional space in the I/O rack.
Open Architecture CNC Uses Profibus
Advanced Technology & Research (ATR) Corp., a high- technology company in Burtonsville, Md. recently received a contract from General Motors Powertrain to provide an Open Architecture Controller to support its work on the Next Generation Inspection System Project (NGIS II). This project is a consortium of Ford, General Motors, Pratt & Whitney, sensor and probe providers, and open architecture controller providers.
Providers of probes, machine monitors, and sensors interface to the controller through open APIs (application program interfaces) developed through NGIS.
The speed and determinism of Profibus DP are well within the requirements for this system. Also, the existing parallel field wiring was not in good enough condition to reuse.
modular fieldbus couplers and 2- and 4-channel blocks allow for easy configuration of the nodes according to the mix of I/O points.
--Judson P. Malone, ATR Corp.
Profibus Gains Worldwide Acceptance
Beginning its fourth year of rapid growth in North America--its ninth worldwide--Profibus is now supported by nearly 900 products, and chip sales of nearly 800,000! According to Michael Bryant, executive director of the North American-based Profibus Trade Organization (PTO), major milestones have included GM-Europe selecting Profibus as the core fieldbus technology for its factories, PTO membership surpassing 150 corporations last fall, and the certification of Profibus as European Norm EN50170.
showing automation products in application from companies worldwide, and global users will experience what North American users did at ISA: fully interoperable, fully deliverable products and systems, and that's really the key.'
For more information contact the PTO in North America at Fax 602/483-7202; or the PNO in Europe at Fax +49 721 965 8589; or visit the worldwide web site at www.profibus.com
A new Profibus interface card connects this weight controller to programmable controllers. The instrument provides power to strain gauge load cells, receives and digitizes the weight signal, and displays weight locally. The PLC has full access to weight data, and can download a variety of parameters, including setpoint values and tare functions.
This absolute multiturn encoder is programmable and has advanced alarm and warning functions. It has a resolution of 13 bits per revolution (8,192 positions) as well as 12-bit rev counting, which is to say it will count 4,096 revolutions before it restarts from zero. It connects via Profibus DP for intelligent communication with a machine control system.
LEINE & LINDE AB
High Cables for Profibus DP
The Unitronic Bus cable is a family of three Profibus DP cables for different types of installations: stationary in-door, stationary outdoor, and one for indoor flexible installation. All have a single pair of low capacitance conductors with an impedance of 150 ohms.
Profibus Terminal Blocks
ET-200L terminal I/O blocks have an integral Profibus DP interface and 16 I/O channels in a combined terminal block and electronics module. For analog signals, a 'Smart Connect' system allows users to expand the ET-200L, and plug in up to eight modules for 16 additional analog channels of I/O.
Profibus: A Brief Overview
Profibus is Siemens' evolution of the ET 100 and ET 200 remote proprietary bus. It is a DIN standard and is in the hands of two organizations, PNO (Europe) and PTO (North America).
ee buses are large and can literally handle half a million I/O points. They fit well into the control pyramid paradigm.
eters to 12 Mbits/sec at 500 meters (the latter requires special transceivers).
Source: Understanding Device-Level Buses, by Bob Svacina, Turck, Inc.; http:\\www.turck.com
PROFIBUS-DP AT A GLANCE
Maximum of three masters
Maximum 126 nodes
Distances up to 10 km
Speeds up to 12 MBps
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