User`s manual

Western Reserve Controls 1782-JDM User’s Manual
PUB 24.0
10
Table 3-3 Serial Port Connections
Pin # RS232
Signal
RS485
Signal
Designator
1 Transmit Signal + SIG+
2 Receive Signal - SIG-
3 Ground Ground GND
3.4 Power Requirements
3.4.1 Device power
The ASCII is powered directly from the DeviceNet connection 11-25 Vdc power supply. The ASCII-1 and
ASCII-2 consume 67 mA of current at 24 Vdc, or 1.8 Watts, typical. The ASCII-3, the isolated RS-232
version, supplies isolated power for the serial link and consumes xxx mA of current at 24 Vdc, or xxx
Watts, typical.
Using the external power source reduces the load on the DeviceNet power supply and provides a degree
of electrical isolation between the ASCII and the network.
Power to and from the field actuators and sensors connected to the ASCII circuits is supplied by the user
from the field wiring. No other external power supply is required to operate the ASCII.
3.5 Network Configuration
DeviceNet specifications provide for a maximum network distances for the main trunk line and
drop lines, depending upon the baud rate used on the network. They are:
Table 3-4 Network Maximum Lengths
Trunk Line Length Drop Length
Maximum Distance Maximum Cumulative
Baud Rate
Meters Feet Meters Feet Meters Feet
125k baud 5OO m 164O ft 6 m 2O ft 156 m 512 ft.
25Ok baud 25O m 82O ft 6 m 2O ft 78 m 256 ft.
5OOk baud 1OO m 328 ft 6 m 2O ft 39 m 128 ft.
3.5.1 Network Termination
A DeviceNet system
must be terminated at each end of the trunk line
. The host controller and
the
last
JDM or other DeviceNet device on the network must always be terminated to eliminate reflections,
even if only two nodes are present. The DeviceNet specifications for the terminating resistor are:
•
121 ohm