Siemens S5-135U/155U System Manual page 482

Analog Input/Output Modules
Configuring
You must observe the following when configuring systems:
Switching on
Switching off
Switching Off the
You should observe the following instructions for switching off CCs and
CC
equipment for supplying power to the enable inputs.
Separate or
When there is a need to switch off the load power supply separately without
Common
affecting the enabling of modules, there are the following possibilities for
Shutdown of the
producing the enable voltage. These exist even when the load power supply
CC/EU and Load
is used without an additional capacitor and common shutdown.
Power Supply
Supply for the enable inputs from:
a) 6ES5 951-4LB11 load power supply
b) Battery
c) Terminals for 24 V on the front plate of the power supply
9-100
At the latest 100 ms after power-up of the PLC, the voltage
must be present at the enable inputs of the I/O modules.
When the PLC has been switched off, the voltage at the
enable inputs of the I/O modules must still be present as
long as the internal 5 V voltage is present.
However, you must ensure that the 24 V load supply for
analog output modules is switched off together with the
PLC. If the supply voltage is still present at the modules
and the PLC is switched off, the output values can drift.
(The analog holding elements for the outputs will no lon-
ger be refreshed with the current value, because there is no
5 V supply to the modules from the bus.)
230 V AC supply for CC/EU and load power supply
a)
–951
Power Supply
230 V AC
Load Power Supply 24V
b)
I/O Modules
F+
CC/EU
L+
L+
C79000-G8576-C199-06
Battery
c)
System Manual