Webdyn WebdynSunPM User Manual page 31

• On installations requiring short lengths with no electric interference, plan on using a 2
pair 6/10 rigid screened cable.
• On larger installations of which the cable length is less than 500 m, plan on a 2 pair
8/10 rigid screened cable.
• When the cable distance is more than 500 m, and even more so if there is electric
interference, plan for a shielded 2 pair 0.34 mm2 cable
The maximum RS485 bus length is 1000 metres. (for 19200 bauds max)
If the length is long, remember to reduce the device transmission speeds if
communication is difficult.
Recommendations for RS485/RS422 BUS wiring:
• The modules must be connected one after the other.
• Star connections are prohibited.
• The cables must either be screened or shielded, twisted pair per pair (see above: "cable
type for RS485 bus connection").
• The cable screen or shielding must be connected to the concentrator box earth and not
to the 0 V (only connect one end of the screen).
• Avoid any return trips in the same cable.
Concentrator side RS485 wiring:
1. Strip the RS485 communication cable sheath over about 4 cm.
2. Shorten the shielding down to the cable sheath.
3. Strip the wires over about 6 mm.
4. Connect the conductors to the terminal block marked "Serial" following the
assignments in your RS485 communication bus.
2-wire RS485 wiring (Half-Duplex):
This is the most common RS485 standard use. A single pair of wires is used for data
transmission and reception. Several systems are linked in bus form as shown on the following
figure. Different RS485 systems use different notations to indicate the correct connection
form per differential communication pair. The following figure shows some of the notations
used.
Version 2.05
préliminaire
USER MANUAL – WebdynSunPM
31