Sensor systems 2 AS-Interface

AS-Interface - Introduction
20
STEP 1
STEP 2
1.5 Configuration and installation of a system
with AS-Interface in 4 steps
Does the system size fit?
The number of inputs and outputs needed must fit the number of AS-Interface
networks. With a full load of 62 4E3A modules, 248 inputs and 186 outputs
within an AS-Interface network are possible. If, however, due to local
system layout, not all the input or outputs on a slave are used, or if analogue
modules or standard slaves are connected, the number of addresses is reduced,
since these slaves "use up" an entire address. If safety-related components
are integrated, these must be connected to safe slaves, which also
require an entire address. If the diagnostics of the safety monitor need to be
interrogated at the master, then the monitor must also be assigned a full address.
In time-critical applications, the B address can be left free, so that the
A-addressed slave can be interrogated on every cycle, this allows a cycle
time < 5 ms (instead of < 10 ms) even at full load. These rules influence the
possible number of total inputs and outputs.
If the number of nodes on one AS-Interface network is insufficient, then a
double master can also be used to drive two AS-Interface networks. Masters/gateways
installed in parallel in the control cabinet can also enable simple
fulfilment of the required system size. If signals from one AS-Interface
network need to be transferred to a second one, data coupler modules can
be used, which transfer 4 bits at a time from one network to the other.
In extensive installations, line lengths of over 100m (this includes spur lines
to intelligent sensors) may be necessary. By using repeaters (maximum of
2 in series), the length of the line can be extended to up to 300 m from the
master. One or two additional power supplies (or power extenders) will be
necessary. A network with star topology, with more repeaters, can attain
very large overall line lengths. The topology of the network is arbitrary: Star,
tree, line, spur lines, or other.
Specifying the power supply
The power supply needed can be derived from the power consumption of
the individual devices. The following typical values can be used:
Current consumption by the master: approx. 200 mA
Per AS-Interface module: approx. 30 mA … 80 mA
(depending on type)
Per sensor input: approx. 5 mA
Per sensor: ca. 10 mA … 80 mA (depending
on type)
(inductive typically 10 mA,
optical typically 35 mA)
Per analogue module: approx. 80 mA
Per safety monitor (1/2 channel): 150/200 mA
This makes it possible to estimate whether a 2.8 A, a 4 A or an 8 A AS-Interface
power supply will be necessary. Exact power consumption data can
be found in the corresponding data sheets.
If a 24 V auxiliary power supply is also necessary, the power consumptions
must also be totalled for it, and a corresponding 24 V power supply selected.
Subject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
Pepperl+Fuchs Group Tel.: Germany +49 621 776-0 USA +1 330 4253555 Singapore +65 67799091 Internet http://www.pepperl-fuchs.com
Issue date 2004-11-19 - Catalogue AS-Interface 2004/2005