14
Commander SK Advanced User Guide
www.controltechniques.com Issue Number: 9
5.2.3 Terminating
resistors
When using either of the above converters, or any other suitable converter with Commander SK, it is recommended that no terminating resistors be
connected on to the network. This applies to any of the drives on the network and also any converter used. It may be necessary to disable the
terminating resistor within the converter depending on which type is used. The information on how to disable the terminating resistor will normally be
contained in the user information supplied with the converter. Terminating resistors are of little or no value when used on EIA485 networks operating
at or below 38.4kBaud.
5.2.4 Isolation of the communications port
5.2.5 Isolation
devices
Isolation devices are available from the following suppliers:
•
OP232/B1 Isolator
www.scimar.co.uk
E-mail: [email protected]
•
232SPM14 Isolator - 4 channel
•
95POP2 Isolator - 2 channel
www.bb-elec.com
www.bb-europe.com
CT Comms cable is also isolated (CT part number 4500-0087)
For users of Commander SE, the serial link for the Commander SK is identical to that of the Commander SE.
5.3 Serial communications connections
If more than one drive is to be connected to a serial link, make the connections as shown in Figure 5-1. (The network should be a daisy chain
arrangement and not a star arrangement, although short stubs are allowed.)
Pin 4 of the RJ45 connector (+24V) can be connected together through the RJ45 cables, but there is no power sharing mechanism between drives
and therefore the maximum power available is the same as for a single drive. If pin 4 is not linked to the other drives on the network and has an
individual load, then the maximum power (100mA) can be taken from pin 4 of each drive.
The serial communications cable must be shielded. The shields must be connected as shown in Figure 5-1.
A data communications cable should not be run parallel to any power cables, especially ones that connect the drive to motors. If parallel runs are
unavoidable, ensure a minimum spacing of 300mm (12in.) between the communications cable and the power cables.
Cables crossing one another at right-angles are unlikely to give trouble. The maximum cable length for a EIA485 link is 1,200 metres (4,000 feet).
If the serial communications cable is longer than 30 metres (100ft), the following must be adhered to:
•
Shielded cable must be used
and either
•
Do not connect the drive 0V to ground at the drive
or
•
Provide isolation from ground at remote / master communications device
If more than one drive is connected to a host computer/PLC etc. each drive must have an unique serial address (see Pr
on page 139). Any
number in the permitted range 0 to 247 may be used but addresses with zero in them should not be used as these are used in drive group addressing.
When using the communications port with a personal computer or centralised controller e.g. PLC, an isolation device must be included
with rated voltage at least equal to the drive supply voltage. Ensure that the correct fuses are installed at the drive input, and that the drive
is connected to the correct supply voltage.
If a serial communications converter other than the CT Comms cable is used to be connected to other circuits classified as Safety Extra
Low Voltage (SELV) (e.g. to a personal computer), a safety isolating barrier must be included to maintain the SELV classification.
WARNING
NOTE
NOTE
NOTE
NOTE
NOTE
NOTE
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