GE Industrial Solutions OKCV3000CN DeviceNet - Manual (Page 54)

GEl-100343
Power Tap
A power tap connects the power supply to the trunk line. Power taps differ from device taps in that they can
contain the following:
-
A Schottky Diode which connects to the power supply Vi- and allows for multiple supplies to be connected
(this eliminates the need for custom power supplies).
-
Two fuses or circuit breakers to protect the bus from excess current which could damage the cable and
connectors.
When connected to the network, a power tap may have the following:
-
Provides a continuous connection for the signal, drain and V- wires
-
Provides current limiting in each direction from the tap
-
Provides a connection to the shield/drain wire for grounding the network
The following figure illustrates the components of a DeviceNet power tap. Power Taps may be more simple for
systems using single power supplies.
Power Tap
Sianal
Sianal
Shield/Drain
L
Fuse
I.
A
—
Fuse
L Schotty
diode
Supply cable
or wires
I
I
Network
supply
Figure D. 1: DeviceNetPower Tap Components
Length
Maximum trunk line length depends upon the data rate and the type of cable (thick or thin) used. The cable
distance between any two points in the cable system must not exceed the Maximum Cable Distance allowed for
the baud rate. For trunk lines constructed of only one type of cable, refer to the table below to determine the
Maximum Cable Distance based on the data rate and the type of cable used. Cable distance between two points
includes both trunk line cable length and drop line cable length that exists between the two points.
Oata rate
Max Cable distance for
100% Thick cable
Max Cable distance for
100% Thin cable
125 kbaud 50Gm
lOOm 250 kbaud 250m
500 kbaud lOOm
TNetl60
APPENDIX D