SMA 485PB-NR - Handbuch (Seite 24)

SMA Technologie AG Retrofitting the Communication Interfaces
Short Description PB-NR-IXX073014 Page 24
Description of the jumpers A, B and C for RS485
Jumper Description Remarks
A 120 Ohm termination
resistor between con-
nector 2 (Data+) and
connector 7 (Data-). Mount jumper "A" on the last inverter on the
RS485 bus in order to terminate the bus. A
120 Ohm connection between connector 2
and connector 7 has the same effect.The in-
stallation of the termination resistor in the
Sunny Boy Control / Sunny Boy Control Plus
is described in the Technical Description of
the Sunny Boy Control / Sunny Boy Control
Plus.
B and C 680 Ohm resisors
between connector 2
(Data+) to +5V and
connector 7 (Data-)
to GND for the pull-
up/pull down resis-
tors. The pull-up/pull-down resistors for the RS485
bus are required only once on the bus. The I-
7520 interface converter has both terminati-
on and pull-up/pull-down resistors integrated
internally - so jumper B and C do not have to
be mounted. In case a different interface con-
verter is used (which is not recommended)
the pull-up/pull-down resistors can be activa-
ted within the Sunny Boy by mounting the
Jumpers B and C.
Note: A RS485 bus must be terminated on each end and must be symmetrized
once. Jumper A in the Sunny Boy terminates the RS485 bus, so only mount this
jumper in the Sunny Boy on the end of the RS485 bus. Jumper B and Jumper
C symmetrize the RS485 bus - mount the jumpers only in one Sunny Boy on the
RS485 bus and only if you are NOT using the I-7520 interface converter. (The
I-7520 has the termination and symmetrizing resistors integrated in the conver-
ter.)
Note: SMA recommends the usage of a I-7520 interface converter for the con-
nection of a RS485 bus directly to a COM port of a PC. Details about this con-
verter are available under www.ICPDAS.com.