34
2.
Installation and wiring
2.7 RS-485 wiring (continued)
The following diagram shows wiring for RS-485 communication.
The configuration of the connection should be either 1:1 or 1:N. If the 1:N connection is Modbus, up to 99 of this
product can be connected. If CompoWay/F, up to 31 can be connected. Enable the terminating resistor that shorts
terminal numbers 7 and 8 in the end unit.
Termination settings
• This unit is equipped with a terminating resistor inside the main unit. On the unit that is the terminator for
communications, short the RS-485 - terminal and the RS-485 E terminal with a cable. Connect with the internal
terminating resistor.
• If the host device you are using does not have its own built in terminating resistor, connect a terminating resistor to
the host device. The terminating resistance is 120
Ω
(1/2W).
• Do not wire in a terminating resistor terminal on KM-N3 that are along the transmission path. This can caused
communication failures.
[Reference]
• If the upstream device does not support RS-485 communications, refer to the table below to select a converter for your purpose.
Important
• The terminal panel is the push-in type. Also read "Cautions when connecting the Push-In Plus terminal
• The addresses for circuits B to D are automatically set, where 1 is added for each circuit in order to the
• A communication address greater than 99 is invalid.
• There is no FG terminal on this product. Connect only the + wire and - wire of RS-485.
• Use twisted pair cables.
• To wire with the RS-485 terminal, use twisted or solid wire of AWG24-16 (with a cross-section of 0.25 to
1.5 mm
2
).
• Peel the wire-coating by 10 mm when using a ferrule terminal and by 8 mm when not using it.
• Use a ferrule terminal with a conductor portion 8mm long.
• To avoid the influence of noise, use separate wiring for the RS-485 communications and for the power.
• The maximum transmission distance is 1200m.
• Irrespective of the transmission distance and number of units connected, perform communications
checks with the actual units.
Protocol
KM-N Setting Tool
USB/RS-485 converter operability confirmed
Modbus
Yes
SI-35USB (LINEEYE Co., Ltd.)
No
CompoWay/F
Yes
No
K3SC-10 (Omron), SI-35USB (LINEEYE Co.,Ltd.)
RS-485
RS-485
RS-485
Communications master
(host device)
+
−