The DeviceNet protocol dramatically reduces costs by integrating up to 62 devices on a 4-wire trunk network. Communications data is carried over two wires with a second pair of wires carrying power. Discrete and analog devices may be connected into the DeviceNet protocol.
DeviceNet
Features
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More than 30% savings in installation costs over conventional systems.
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Capability to handle both analog and discrete valve and instrument applications.
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Power and communication supplied over the 4-wire bus. Capability to install up to 62 devices on the same bus network.
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Electronic Data Sheet provides accurate device configuration details.
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Hot insertion of field devices without dropping power. (General purpose environments)
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Message prioritizing to enable fast throughput rate for critical information.
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Technology with proven reliability in millions of mission critical applications.
DeviceNet Economic Analysis
Sizable installation savings are realized over conventional
systems when installing a DeviceNet network. The following is an estimate of
installation costs of a conventional system versus DeviceNet (costs are
listed in the amount per device):
This analysis is typical of an installation of 20 automated valve systems
located in a cluster approximately 150 feet from the I/O rack. Each of the
automated valves is located 20 feet apart in the cluster.
The StoneL DeviceNet I/O module and VCT have an auxiliary 4 to 20mA input
that is bus powered. (No additional power is needed.) Other analog
instrumentation such as flow meters, level controls, pressure sensors, etc.
may be wired directly into the module, cutting installation costs further.
DeviceNet Economic Analysis
When adding an analog device to an existing StoneL DeviceNet VCT, a convenient connection may be made to the nearest device. In
this example, the level control was 20 feet from the StoneL DeviceNet VCT and 150 feet from the central controller.
DeviceNet
System Specifications
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Topology |
Trunk line with drops and/or branches |
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Cabling |
Two separate shielded twisted pairs contained in one shielded cable; may be thick trunk, thin trunk or flat cable |
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Base Technology |
CAN (Controller Area Network) |
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Number of Devices |
62 per network |
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Data Delivery |
8 bytes of data for I/O; more if device supports fragmentation |
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Power;
Thick Cable
Thin Cable |
8 Amps @ 24 VDC
4 Amps @ 24 VDC |
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Cable Length (Thick) |
Dependent on data rate and cable type
(see table below) |
Data Rate
125 Kbaud
250 Kbaud
500 Kbaud |
Trunk Length
500m(1,640ft)
250m(820ft)
100m(328ft) |
Drop Length
Maximum
6m(20ft)
6m(20ft)
6m(20ft) |
Drop Length
Cumulative
156m(512ft)
78m(256ft)
39m(129ft) |
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Cable Length (Thin) |
100m (328ft) |
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Communication Methods |
•Master/Slave Polling
•Cyclic Polling
•Change of State
• Strobed I/O
• Explicit Messaging |
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Data Signal |
Square wave digital with non return to
zero encoding |
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Error
Detection |
Automatic retransmission of corrupted
messages and autonomous switching off of defective nodes |
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Address Setting |
On-line via DeviceNet configuration
software and PC interface module; off-line with dip switches |
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Support Organization |
Open DeviceNet Vendor Assn.
www.odva.org |
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