CLIVET WSHN-EE 21 - Page 28

pag 28
12. UNIT INTERFACE VIA RS 485
Below the indications for the serial connection ; refer anyway to the CLIVET “RS 485 NETWORKS –
GUIDELINES” document and ask for the COMMUNICATION PROTOCOL about the COMPACT electronics
- The total length of each single serial line,
don’t have to be over 1000 metres
- The potential difference between the “ground”
of two RS485 switches must be less of 7 V
- Couple of conductors twisted and shielded
- Section of conductor 0.22mm
2
…0,35mm
2
- Nominal capacity between conductors < 50
pF/m nominal impedance 120 Ω
- Recommended cable BELDEN 3105 A
TYPE OF NETWORK
The serial lines must be connected in bus typology, i.e. nodes to more points are not admitted
SHIELD
- It must be connected to a ground without
disturbances
- Connected to round in only one point
- Provide to the shield continuity during all the
serial cable extension.
12 V AC
C
N
1
C
N
1
1
9
1
8
2
0
2
1
2
0
1
8
1
9
2
1
RS-485
RS-232
gnd
-
+
Supervisor
TTL /
RS485
+
-
TO OTHER
UNITS
12 V AC
gnd
TTL /
RS485
-
gnd
+
OK
NO !
Sistema di supervisione