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Chapter 11

Chapter 11. Introduction to DeviceNet. DeviceNet Purpose. Open network Link low-level devices to PLCs Sensors Pushbutton stations Distributed I/O blocks Intelligent motor started overloads Variable frequency drives. DeviceNet Open Network. Open network

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Chapter 11

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  1. Chapter 11 Introduction to DeviceNet

  2. DeviceNet Purpose • Open network • Link low-level devices to PLCs • Sensors • Pushbutton stations • Distributed I/O blocks • Intelligent motor started overloads • Variable frequency drives

  3. DeviceNet Open Network • Open network • Network devices (nodes) can be purchased from many different vendors • Network managed by Open DeviceNet Vendors Association (ODVA) • ODVA.ORG

  4. DeviceNet Advantage • Save wiring costs • Rather than run power wires separately to each device • Rather than run signal wires from each field device separately back to PLC, I/O module connect devices directly to a network • One cable with four wires • Two power wires • Two signal wires

  5. Field Devices More Intelligent • Traditional systems • A photo switch counting pieces as they pass on a conveyer was wired directly into an input module. • Counter programmed on ladder to track parts’ count • Counter done bit triggered output point to control field action

  6. DeviceNet Advantage • Many DeviceNet devices are intelligent. • Photo switch has counters and timers incorporated into sensor. • PLC does not need to have timer or counter on ladder. • When timer or counter is done, the action is carried out through RSNetWorx for DeviceNet software to trigger field device across the network.

  7. DeviceNet Components • PLC with DeviceNet scanner • RSNetWorx software for DeviceNet • Trunk line • Drop lines • Nodes • Minimum one power supply • Two 121-ohm ¼-watt termination resistors • Up to 64 nodes

  8. DeviceNet Network Example Cable to open-style connector on network PLC scanner Prox switch and cable Stack light KwikLink cable Power supply Termination resistor ArmorBlock maximum 4 I/O points Termination resistor Insulation displacement connector Open-style connection for power supply CompactBlock I/O module RightSight photo sensor

  9. Sample of Some DeviceNet Media Components Thick round drop line cable Device port T-port KwikLink drop line cable KwikLink flat trunk line cable KwikLink flat trunk line cable insulation displacement connector DeviceLink

  10. DeviceNet Cabling • Thick round • Thin round • KwikLink cable • Special-use cable • Open-style connectors

  11. Thick Round Cable • Used for trunk line • T-ports used to connect from trunk line to drop lines

  12. Thin Round Cable • Typically used for drop lines • Can be used for trunk in short networks with low current requirements

  13. KwikLink DeviceNet Connection Insulation displacement connector KwikLink flat cable

  14. Insulation Displacement Connection • For non-wash down • Typical usage conveyor lines • Mount on inside rail of conveyor • No conduit needed • Easy installation of new nodes • No minimum spacing

  15. DevicePort • Passive 4- or 8-point taps • Connected to trunk line by drop line • Previous slide showed an 8-point DevicePort • Nodes connected to DevicePort by drop lines

  16. T-port • Used to connect drop line to trunk line • Drop line connected to DevicePort and then on to multiple nodes • Drop line connected directly to node • Maximum drop line length 20 feet

  17. DeviceLink • Adapter to interface non-DeviceNet devices to network • 2- or 3-wire 24-V sensors • Mechanical limit switches • Any non-DeviceNet device with relay contacts • One required for each non-DeviceNet node

  18. Additional Media • Refer to the DeviceNet Media catalog for a complete listing of available products.

  19. Maximum Trunk Line Length (1 of 2) • Maximum cable distance between any two nodes • Not necessarily actual length of backbone • Maximum length determined by cable type and baud rate

  20. Maximum Trunk Line Length (2 of 2)

  21. Trunk Line Calculation One Node number

  22. Example One • Left terminating resistor to node 1 is 12 feet. • Drop line node 1 is 2 feet. • Right terminating resistor to node 12 is also 12 feet. • Node 12 drop line is 2 feet. • From node 1 drop line to node 12 drop line is 800 feet.

  23. Trunk Line Calculation (1 of 2) • For this example, trunk line length is maximum length of cable between terminating resistors.

  24. Trunk Line Calculation (2 of 2) • 12 + 800 + 12 = 824 feet • Refer to table for maximum baud rate of network.

  25. Maximum Trunk Line Length Trunk line length is over 820 feet so maximum baud rate for this network is 125 K.

  26. Power Supply 300 ft 20 ft 2 ft 3 ft 11 8 ft 6 ft 7 8 12 ft 3 9 12 6 1 4 2 10 13 5 Node numbers 14 Trunk Line Calculation Two

  27. Example Two • Left terminating resistor to node 1 drop line is 20 feet. • Node 1 drop line is 6 feet. • Right terminating resistor to node 12 drop line is 2 feet. • Node 12 drop line is 8 feet. • Trunk line from node 12 drop to node 14 drop line is 3 feet. • Node 14 drop line is 12 feet. • Node 1 trunk line to node 14 is 300 feet.

  28. Trunk Line Calculation • For this example, trunk line length is maximum length of cable between any two nodes or terminating resistors. • Assume round thick trunk line. • Look at network again.

  29. Power Supply 300 ft 20 ft 2 ft 3 ft 11 8 ft 6 ft 7 8 12 ft 3 9 12 6 1 4 2 10 13 5 14 For this example, trunk line length is maximum length of cable between any two nodes or terminating resistors. Trunk Line Calculation Two (1 of 2)

  30. Trunk Line Calculation Two (2 of 2) • The longest cable distance is between the left terminating resistor and node 14. • For this example, the distance between terminating resistors would not be the correct calculation. • 20 + 300 + 12 = 332 feet • Refer to table for maximum baud rate of network.

  31. Maximum Trunk Line Length (1 of 3) Trunk line length is over 328 feet so maximum baud rate for this network is either125 K or 250 k.

  32. Maximum Trunk Line Length (2 of 3) • The rule is to go back 20 feet from the termination resistors and see if there is a drop line that is longer. • If a drop is longer, then it must be included in the trunk line calculation. • Remember maximum drop line length is 20 feet.

  33. 8 7 15 3 4 20 feet Maximum Trunk Line Length (3 of 3) • Terminating resistor and node 00 is 3 feet. • Node 00 and node 1 is 4 feet. • Trunk line to node 7 is 15 feet. • 15 foot drop is longer than 3 +4 for trunk.

  34. Cumulative Drop Line Length (1 of 2) • Sum of all drop lines • Maximum drop line length to any one node • 20 feet • Cumulative drop line length also determines network baud rate

  35. Text figure 11-30 Cumulative Drop Line Length (2 of 2)

  36. Total All Drop Line Lengths (1 of 2)

  37. Total All Drop Line Lengths (2 of 2) • Cumulative length is 131 feet. • Nodes 10, 13, and 14 exceed the 20-foot maximum drop to any 1 node. • Shorten up cable. • Cumulative drop line length is now 127 feet. • Refer to the table for maximum baud rate for network.

  38. Cumulative drop line length is 127 feet. Cumulative Drop Line Length

  39. Power Calculations • Add up total device current • Determine trunk line length • Cable type • How many power supplies and where mounted • Look up tables for power allowed on network • Full calculation method available for additional accuracy

  40. Common Problems With DeviceNet Networks (1 of 2) • Improper installation • Trunk line length correct? • Cumulative drop line length correct? • Power supply proper size? • Overdriving network with too much information flow? • Refer to DeviceNet Cable System Planning and Installation Manual from Rockwell Automation Web site.

  41. Common Problems With DeviceNet Networks (2 of 2) • Network modification after installation • Trunk line length recalculated? • Cumulative drop line length recalculated? • Power supply recalculated? • Overdriving network with too much information flow?

  42. DeviceNet Interface

  43. FlexLogix PLC DeviceNet Daughter Card DeviceNet open-style cable connection point Set baud rate Status LEDs Set interface card’s node

  44. CompactLogix DeviceNet Scanner DeviceNet scanner Open-style cable connection CompactLogix processor CompactLogix is a member of the ControlLogix family.

  45. ControlLogix Modular Interface 1756-DNB • ControlLogix modular chassis interface module • 1756-DNB • DeviceNet bridge module Information window Status LEDs Open-style network connection

  46. Example of Rockwell Automation PLC DeviceNet Interface Modules • SLC 500 DeviceNet scanner • 1747-SDN • PLC 5 DeviceNet scanner • 1771-SDN

  47. Example of General Electric PLC DeviceNet Interface Modules • Series 90-30 PLCs • DeviceNet master module • IC693DNM200 • VersaMax PLC • Remote I/O DeviceNet network interface • IC200DB1001

  48. Personal Computer DeviceNet Interface • Computer type determines interface needed. • Notebook uses PCMCIA such as a Rockwell Automation 1784-PCD. • Desktop or industrial computer would require a DeviceNet 1784-expansion card. • Computer with serial port could use Rockwell Automation 1770-KFD interface box.

  49. 1770-KFD Interface Desktop or notebook computer with serial port SLC 500 1747-SDN Interface cable plug Open-style connector to DeviceNet network Interface cable KFD to serial port interface cable 1770-KFD

  50. SLC 500 1747-SDN Notebook personal computer Interface cables PCMCIA interface card 1784-PCD Open-style connector to DeviceNet network 1784-PCD Card

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