CONNECTION TO THE FIELDBUS. Enertronica Santerno Sinus Penta, SOLARDRIVE PLUS, IRIS BLUE, PENTA MARINE

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11.7.2. Connection to the Fieldbus

The wiring quality is fundamental for the best reliability of the bus operation. For CANopen wiring, a shielded twisted pair with known resistance and impedance is recommended. The conductor unit is also fundamental for the quality of the signal. The higher the baud rates, the shortest the bus lengths allowed. The maximum length of the bus is also affected by the number of nodes. The tables below indicate the cable specifications based on the cable length and the variation features of the max. length based on the number of nodes and the cross-section of the conductors.

Tables refer to copper wires with a characteristic impedance of 120



and a typical propagation delay of

5ns/m.

Bus length [m]

Max. specific resistance of the cable [m



/m]

Recommended cross-section for conductors [mm 2 ]

Recommended terminator resistance [



]

Max. baud rate

[Kbit/s]

0÷40

40÷300

300÷600

600÷1000

70

60

40

26

0.25÷0.34

0.34÷0.60

0.50÷0.75

0.75÷0.80

124

150÷300

150÷300

150÷300

1000 kbit/s

500 kbit/s (max 100m)

100 kbit/s (max 500m)

50 kbit/s

The total resistance of the cable and number of nodes determine the max. allowable length for the cable as per static features, not for dynamic features. Indeed, the max. voltage delivered by a node with a dominant bus is reduced by the resistive divider consisting of the cable resistor and the terminator resistors. The residual voltage must exceed the dominant voltage of the receiving node. The table below indicates the max. length values based on the cable cross-section, i.e. the cable resistance, and the number of nodes.

Cross-section of the conductors [mm 2 ]

Max. wiring length [m] based on the number of nodes n. nodes < 32 n. nodes < 64 n. nodes < 100

0.25

0.50

200

360

170

310

150

270

0.75 550 470 410

The B40 Fieldbus DeviceNET board is equipped with a DIP-switch allowing inserting the termination resistor on the bus. This DIP-switch is to be inserted only in the first and last device in a DeviceNET trunk.

Each DeviceNET trunk line must meet some geometric requirements and must

NOTE provide two terminator nodes provided with suitable resistors. Consult document

PUB00027R1 “Planning and Installation Manual - DeviceNetTM Cable System” and all the application notes available from ODVA web site

( http://www.odva.org

).

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