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Operating Instructions
ISD 230/260/280 IR Data Transmission Systems
Chapter
5
© SICK AG · Auto Ident · Germany · All rights reserved
8 008 207/30-11-2001
40
Electrical installation
Line termination (RS 422/485)
RS 485/Profibus (L2-DP):
If one of the ISD 260 or ISD 280 units is the last device at the line end of the electrical
bus, the unit can be terminated. A defined line termination is then connected internally for
the receiver in the unit to enhance the signal-to-noise ratio.
The terminating resistors can be integrated with the DIL switches S 2.1 and S 2.2, as
shown in
Table 5-8, Page 34
. The resulting circuit is shown in
Fig. 5-4
. If possible, the
termination should be provided in the Profibus connector directly.
RS 422/Interbus-S:
In this point-to-point configuration, the terminating resistors must be connected to the
receivers on both stations.
Fig.
5-14: ISD 260/280: Line termination for the RS 485 interface
5.2.7
Connecting the functions interfaces
The ISD 260 and ISD 280 are equipped with one switching output and one switching input
per unit. These have the following functions:
•
A signal level of +24 V is pending at the “Light path free“ switching output if the light
path is uninterrupted and light reception from the opposite station is adequate.
If the light path is interrupted completely, e.g. due to an obstacle, or if the intensity of
the light received from the opposite station is too low due to an object in the light path
or because the distance between the two stations is too large, the output is disabled
(signal level 0V).
The output has the same functionality as the “Light path interrupted“ LED at the top of
the front panel on the device but does not flash in the transition range.
Last device
at end of bus
1) electrically isolated form the
supply voltage
2) to EN 50 170 for Profibus
R+/T+
or B
2)
R–/T–
or A
2)
Receiver
ISD 260/280
S2.2 (Term–)
S2.1 (Term+)
Host
ISD
ISD
➚
. . .
+5V
390
Ω
390
Ω
220
Ω
3
8
GND
GND
1)
+5 V
1)
RS 485
Configuration
and
electrical
installation
of
the
ISD
260/280