or Identification Numbers, are numbers identifying data that
can be transmitted between SERCOS nodes and hosts. Design of
a successful SERCOS network requires a thorough knowledge of
all IDNs used.
are two types of IDNs. SIDNs (standard IDNs) are defined
by the SERCOS specification. These IDNs represent data that
is commonly used in drive implementations. It should be noted
that it is up to the manufacturer to decide which SIDNs it will
support. PIDNs (product IDNs) are defined by the manufacturer.
These IDNs represent data used in the drive for features not
discussed in the SERCOS specification. PIDNs vary widely between
drives and manufacturers.
initialization of a SERCOS network, many drives require the
setting of certain IDNs. Please consult the drive manufacturer's
documentation concerning required IDN settings.
in cable length and material have a profound influence upon
power attenuation within networks:
optic cable length-- the longer the cable, the more optical
power it absorbs.
optic cable material (glass vs. acrylic)-- different materials
absorb different quantities of light, and react differently
to changes in temperature, bend radius, etc.
affects transceiver and cable characteristics.
movement / bend radius--
as fiber optic cables are moved between motion components,
their bend radii will vary. This, in turn, can attenuate optical
signals. Generally, the smaller the bend radius, the higher
the power attenuation. Cables attain their maximum optical
efficiency when they are straight.
for SERCOS fiber-optic cable are found in Section 5.3.3 of the
SERCOS interface standard (IEC 64191); however, network designers
should consult their vendors for exact cable characteristics.
Depending upon the cable material used (glass vs acrylic), length
and bend radius, performance will vary. Section 5.3.5 of IEC
61491 specifies system data of the optical transmission path.
Conforming cables must meet this specification.
controllers utilize screw-on connectors having 1/4 - 36 UNS
2A threads. Typically, transceivers use molded plastic threads,
while many cable connectors are steel; therefore, use caution
to prevent cross-threading and stripping.
connectors do not efficiently couple the fiber-optic cable's
light energy to a transceiver and can cause data corruption.
Under no circumstances should connectors
be left loose. (This includes situations where a
transceiver's power output is too high and can be reduced by
loosening the connector; this is NOT a reliable way to adjust
integral part of building a SERCOS ring is establishing optimal
transmitting power for each device in the ring. Starting at
the XMP controller, an optical control signal is transmitted
at a specified power level. The first device in the ring receives
this signal, copies and processes it, then generates a new
transmission. The next device in the ring receives this secondary
transmission, processes it, and so on. This relay continues
through every device until the controller becomes the last
device in the ring. The controller processes the telegrams
it has received, calculates new control commands, then transmits
new telegrams during the next data cycle. The process repeats
until halted by the controller, or an interruption in the
ring causes a fault.
building SERCOS networks, it is crucial to match the power
of each device's transmitter with the downstream device's
receiver. If power levels are set too low or too high, data
corruption can quickly result--a common cause of errors and
problems in SERCOS networks.