1. Korbin Blunck November 19,2012
Fieldbus
Korbin Blunck
November 19,2012

2. What is Fieldbus?
Fieldbus is the application layer in a network system used to interface devices in a network with a PLC or HMI.

3. Current State
Fieldbus is an industrial computer network which is used for real- time distributed control
There are several different standards currently on the market with each having their own requirements.
Fieldbus devices with different standards cannot be used interchangeably unless used in conjunction with a conversion device such as a gateway.

4. Some of the Current Standards
Profibus
Bitbus
CompoNet
SafetyBus
SERCOS Interface
RAPIEnet

5. Fieldbus Companies

6. Costs Cables can range from the tens to the hundreds of dollars
Nodes and PLC connections can cost thousands of dollars depending on the application

7. Profibus
“The network is a digital, bi-directional, multidrop, serial-bus communication network used to link isolated field devices, such as controllers, transducers, actuators and sensors.
Bi-directional means it is a duplex port; the data can be transmitted in two directions at the same time.
Multidrop is also referred to as multi-access and it can be interpreted as a single bus with many nodes connected to it.
Serial-bus means the data is transmitted serially according to RS232 or RS485 protocol. Profibus uses RS485 protocol.” Ed Red-

8. Profibus (Cont.)
First promoted in 1989 by the German Department of Education and Reasearch
Two main variations are used today in industry:
Profibus DP (Decentralized Protocol)
Used mainly for controlling sensors and actuators on a machine in a factory setting. Pulls all of the information back to a main controller. The bit rate can be varied depending on application ( 9.6 kbit/s to 12 Mbit/s)
Profibus PA (Process Automation)
Is designed to be able to send power to the sensors and actuators in a tightly controlled window for safer operation (used in explosive applications). Sends at a bit rate of kbits/s.

9. Profibus (Cont.)
Cable lengths vary depending on the type of transmission and cable used.
For twisted pair cables the length can be up to 100 to 1200 meters, depending on bit rate used.
Machester Bus Powered can be up to 1900 meters.
Fiber Optic cables can be 15 Kilometers

10. Safetybus Developed from 1995- 1999 by Pilz Gmbh and Co. In Germany
Designed specifically for safety on machines (based on CAN fieldbus)
Factory automation
Amusement park rides
Transportation systems
Basically any area to protect health and life
Meets level SIL 3 according to IEC 61508 

11. Safetybus (Cont.) Max 64 Bus devices on one network
Transmission rate is 20 to 500 kBaud
Cable length can be up to m
Guaranteed error reaction time is 20 ms

12. SERCOS Interface (Serial Real-time Communication System)
Created in 1987 for application in control systems
Used on machinery, assembly systems, robotics, printing, packaging machinery etc.
Meets standard IEC and EN 61491

13. SERCOS Interface (Cont.)
Transmission rate can be up to 32 Kbaud
Can have up to 511 devices on one network
Cable lengths can be 50+ Km, if fiber optic
Can have peer-to-peer communication
Master-master
Slave-slave

14. The Future of Fieldbus
The two main standards that are taking control of the market are Foundation Fieldbus and Profibus
Currently, many fieldbus standards are now using a higher speed Ethernet based protocol, with more developments to be expected.
Many of the fieldbus cables are transferring over to fiber optic cables because they are able to achieve the highest speeds (however, many of the devices limit the speed due to slower transmission)
A few companies have begun to develop wireless fieldbus devices, but are limited by device speeds

15. Class Application
Calculate the time it would take to transfer 64 bits of information on a Profibus PA configuration.

16. Class Application (Answer)
Remember that Profibus PA has a set bit rate of kbit/s
M=64
Use M=2^N
Therefore N=6
Now use Fs=R/N, with R being kbit/s
Therefore Fs= cycles/second
Finally, use Ts=1/Fs
To get: Ts=.192 Miliseconds

17. Technical Paper Fieldbus Technology in Industrial Automation
By JEAN-PIERRE THOMESSE

18. Additional Videos http://youtu.be/m_PoSlC e2DU
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19. Sources http://en.wikipedia.org/wiki/SERCOS_III
_Planning_8012_V10_Aug09.pdf
/literature/documents/um/motion-um001_-en-p.pdf
f2e3c1256f2e004d4aea.aspx