CHAPTER 4

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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
• Network devices (nodes) can be purchased
from many different vendors
• Network managed by Open DeviceNet
Vendors Association (ODVA)
– ODVA.ORG
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
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
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.
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
DeviceNet Network Example
Prox switch
and cable
Stack light
Cable to open-style
connector on
network PLC scanner
KwikLink cable
Power
supply
Termination
resistor
RightSight
photo sensor
Termination
resistor
Insulation
displacement
connector
ArmorBlock
maximum
4 I/O points
Open-style connection
CompactBlock
for power supply
I/O module
Sample of Some DeviceNet Media Components
Thick round
drop line cable
KwikLink drop
line cable
KwikLink flat trunk
line cable insulation
displacement connector
Device port
T-port
KwikLink flat trunk
line cable
DeviceLink
DeviceNet Cabling
•
•
•
•
•
Thick round
Thin round
KwikLink cable
Special-use cable
Open-style connectors
Thick Round Cable
• Used for trunk line
• T-ports used to connect from trunk line to
drop lines
Thin Round Cable
• Typically used for drop lines
• Can be used for trunk in short networks with
low current requirements
KwikLink DeviceNet Connection
Insulation displacement
connector
KwikLink flat cable
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
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
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
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
Additional Media
• Refer to the DeviceNet Media catalog for a
complete listing of available products.
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
Maximum Trunk Line Length (2 of 2)
Trunk Line Calculation One
Node number
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.
Trunk Line Calculation (1 of 2)
• For this example, trunk line length is
maximum length of cable between
terminating resistors.
Trunk Line Calculation (2 of 2)
• 12 + 800 + 12 = 824 feet
• Refer to table for maximum baud rate of
network.
Maximum Trunk Line Length
Trunk line length is over 820 feet so maximum baud rate for this network is 125 K.
Trunk Line Calculation Two
Power Supply
300 ft
20 ft
2 ft
3 ft
11
7
6 ft
8
12 ft
3
6
8 ft
9
12
4
2
5
13
10
Node numbers
14
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.
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.
Trunk Line Calculation Two (1 of 2)
Power Supply
300 ft
20 ft
2 ft
3 ft
11
7
6 ft
8
12 ft
3
6
8 ft
9
12
4
2
5
13
10
14
For this example, trunk line length is maximum length of cable between any
two nodes or terminating resistors.
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.
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.
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.
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.
7
8
15
3
4
20 feet
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
Text figure 11-30
Cumulative Drop Line Length (2 of 2)
Total All Drop Line Lengths (1 of 2)
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.
Cumulative Drop Line Length
Cumulative drop line length is 127 feet.
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
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.
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?
DeviceNet Interface
FlexLogix PLC DeviceNet
Daughter Card
DeviceNet open-style
cable connection point
Set baud rate
Status LEDs
Set interface
card’s node
CompactLogix DeviceNet Scanner
DeviceNet scanner
Open-style cable connection
CompactLogix processor
CompactLogix is a member of the ControlLogix family.
ControlLogix Modular Interface
1756-DNB
• ControlLogix modular
chassis interface
module
• 1756-DNB
• DeviceNet bridge
module
Information
window
Status LEDs
Open-style
network connection
Example of Rockwell Automation
PLC DeviceNet Interface Modules
• SLC 500 DeviceNet scanner
– 1747-SDN
• PLC 5 DeviceNet scanner
– 1771-SDN
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
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.
1770-KFD Interface
Desktop or notebook
computer with serial port
SLC 500 1747-SDN
Interface
cable plug
KFD to serial port
interface cable
1770-KFD
Interface cable
Open-style connector to
DeviceNet network
1784-PCD Card
SLC 500 1747-SDN
Notebook
personal computer
PCMCIA interface
card 1784-PCD
Interface cables
Open-style connector
to DeviceNet network
Use ControlLogix
PLC as a Bridge (1 of 2)
• Most popular interface to PLC for upload,
download, on-line editing is Ethernet
• Ethernet interface card in ControlLogix
chassis(1756- ENBT)
• A 1756-DNB or DeviceNet bridge module in
ControlLogix chassis to communicate with
DeviceNet
Use ControlLogix
PLC as a Bridge (1 of 2)
• Use RSLinx Ethernet driver to get to Ethernet
interface module
• Bridge across ControlLogix backplane to
DeviceNet Bridge module (1756-DNB)
• Out DNB to DeviceNet network
• No separate DeviceNet interface required
RSNetWorx Software
• RSNetworx for DeviceNet software
– Set up network
– Map data flowing on network
– Program, monitor, or modify device
parameters
RSNetWorx for DeviceNet
RSNetWorx View of DeviceNet
Network scanner
Drop line
Termination
resistor
Termination
resistor
Node address
Trunk line
Device or node
on network
Power supply not shown in RSNetWorx
DeviceNet Scan List
• RSNetWorx software
• Scan List is part of scanner properties.
• Any device that is on the network that is to be
scanned by the PLC scanner must be in the Scan
List.
• Network devices are not mapped until placed in the
Scan List by programmer.
– Auto mapping
– Manual mapping
DeviceNet PLC Scanner Properties
ControlLogix
DNB scanner
properties screen
Add or remove
single device to
or from Scan List
Add or remove
all devices to
or from Scan List
Auto map
devices when
add to scan list
Scan List tab
Scan List
Electronic
keying
Available Devices on Network
• When going on-line with a network scanner,
like a 1756-DNB, scanner will recognize
devices currently present on network.
– These devices or nodes will be listed in the
Available Devices view.
– These devices are not in the scan list at this
time.
Auto Map Devices
When Add to Scan List
• Do you want the device(s) to be auto-mapped
when added to the scan list?
• If Automap is selected, you have no control of
how devices are mapped.
• If you uncheck Automap, then devices can be
manually mapped by the programmer.
Electronic Keying
• How close does a replacement device have
to be to the original when replaced?
– Device type
– Vendor
– Product code
– Major revision
– Minor revision
• Minor revision or higher
DeviceNet Data Mapping
ControlLogix
ControlLogix 1756-DNB Mapping
Input tab
Scanner
properties
Click here to
unmap a device.
Input devices
in Scan List
Unused processor
memory. Can be
manually mapped later.
Data mapping
for each node
ControlLogix processor
tags or addresses
where data is mapped.
DeviceNet Data Mapping
• ControlLogix is a 32-bit PLC.
– All tags will be either 32 bits wide or a:
• Word, called an integer (INT) which is16 bits
• Byte, called a short integer (SINT) which is 8 bits
• Minimum memory allocation for any DeviceNet
device is a SINT.
• Node 6 is a bulletin 160 Allen-Bradley Drive.
– Drive has two words of data.
• Drive status information as single bits
• Drive speed feedback represented as 0 to 32767
ControlLogix Input Mapping
32 Bits
16 Bits
31
ControlLogix Tags
16 15
8 7
Node 3 Series 9000
Photo Electric Sensor
mapping
Node 6 Drive Input Status word
Node 6 Drives Speed Feedback word
0
Node 4 Series 9000
Photo Electric Sensor
mapping
ControlLogix Processor
Data Mapping or Tags (1 of 2)
• Node 6 is Bulletin 160, the variable frequency
drive
– Status bits mapped as upper word of
Local:1:I.Data[2].
– Drive Speed Feedback word is mapped as
the lower word of Local:1:I.Data[3].
ControlLogix Processor
Data Mapping or Tags (2 of 2)
• Node 4 is a Series 9000 Photo Switch
mapped as the upper byte of the lower word
at Local:1.I.Data[2].
• Node 3 is a Series 9000 Photo Switch
mapped as the lower byte of the lower word
at Local:1.I.Data[2].
DeviceNet Data Mapping
SLC 500
DeviceNet Data Mapping
• SLC 500 and PLC 5 are 16-bit computers.
– All data will either be a 16-bit word or one byte.
• Minimum memory allocation for any DeviceNet
device is a byte.
• Node 6 is a Bulletin 160 Allen-Bradley Drive.
– Drive has two words of data.
• Drive Command information as single bits
• Drive Speed Command represented as 0 to 32767
SLC 500 Output Data Mapping
1747-SDN
properties view
Output devices
in Scan List
SLC 500 Output Status
Table where data is
coming from
Output mapping tab
Click here to unmap
selected device
Two words or 8
bytes currently
mapped for drive
at node 6
SLC 500 Processor Data Mapping
• Node 6 is Bulletin 160, the variable frequency
drive
– Drive Command bits word is mapped as
O:1.2.
– Drive Speed Command word is mapped as
O:1.3.
Node 2 Output Mapping
• Node 8 is a Rockwell Automation 1792D
compact block output module.
– This compact block has four outputs.
• Output data from SLC 500 mapped to lower
byte of O:1.6.
• Currently upper byte of O:1.6 is available for
another device.
DeviceNet Nodes
General Properties
• Right click on device on RSNetWorx screen.
• General Properties screen is displayed.
– Display I/O data
– Display, monitor, or modify devices
parameters
– View electronic data sheet (EDS file)
General Properties
Parameters
tab
EDS tab
Identifies this device
Current node address.
Node address can be
changed here.
Device’s
identity
Numbers used
to identify EDS file
Device Parameters
Device
Parameters
tab
Lock identifies
read-only
parameters
Parameter
number
Monitor a single
parameter or all
Icons for uploading
or downloading
to device
Click here to
monitor parameter
Current value
of parameter
Parameter Editing
Select parameter
to edit
Options drop-down box
Select
Electronic Data Sheets
EDS Files
Electronic Data Sheets
• Typically referred to as EDS files
– EDS files contain information regarding the
personality of the device.
– Correct EDS file must reside in the device
before it can be a working part of the network.
– EDS file must be the same firmware level as
the device.
If EDS File Is Not Current
• Go to manufacturer’s Web site and download
correct file.
• Go to ODVA.ORG site and download correct
file.
• EDS file numbers represented in Hex.
• Use EDS Wizard to update or register the
network device.
EDS Wizard
Updating a network
Device’s EDS file is to
register the file.
Click next to continue.
Register EDS File
How many
files to register
After download,
browse for file
on you computer.
EDS file name
represented
in Hex
Click next to
continue
registration.
Determine EDS File Name
• After downloading EDS file, the file name is
represented in Hex.
– To determine EDS file to use when registering
file:
• Must know Hex
• Construct file number from RSNetWorx general
properties page
Convert General Properties
Page Device Identity to Hex
[1] = 0001
[6] = 0006
[43] = 002B
[1.004] = 0100
Select Correct EDS File
Select Correct EDS File
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