Siemens LOGO! Series Manual page 51

Special features of LOGO! 12/24RCE/RC/RCo, LOGO! 24/24o and LOGO! 24C/24Co
Fast digital inputs: I3, I4, I5 and I6:
These versions are also equipped with fast digital inputs (up/down counters, threshold
triggers). The restrictions mentioned earlier do not apply to these fast digital inputs.
Note
The fast digital inputs I3, I4, I5 and I6 are the same as in the previous versions 0BA0 to
0BA5; therefore, a circuit program that is written in these versions can be transferred to the
0BA6 or 0BA7 devices with the programming software LOGO!Soft Comfort, without any
changes to these features. In contrast to this, you need to modify circuit programs written for
a LOGO!...L version (fast digital inputs I11-I12). The fast digital inputs have increased from 2
kHz to 5 kHz with the 0BA6 series.
Expansion modules do not have fast digital inputs.
Analog inputs: I1 and I2, I7 and I8:
The inputs I1, I2, I7 and I8 of LOGO! versions 12/24RCE/RC/RCo, 24/24o and 24C/24Co
can be used as either digital inputs or analog inputs. The input mode is defined in the LOGO!
circuit program.
The inputs I1, I2, I7 and I8 provide digital inputs, and the inputs AI3, AI4, AI1 and AI2 provide
analog inputs, as described in the topic "Constants and connectors - Co (Page 138)". AI3
corresponds to the input terminal I1; AI4 corresponds to I2; AI1 corresponds to I7; AI2
corresponds to I8. The use of AI3 and AI4 is optional. You configure your LOGO! to use
either two or four analog inputs as described in topic "Setting the number of AIs in the
LOGO! Basic (Page 299)" in Section 5.2.4.
When using inputs I1, I2, I7 and I8 as analog inputs, only the range from 0 to 10 V DC is
available.
Connecting a potentiometer to inputs I1, I2, I7 and I8
To allow you to achieve 10 V as the maximum value when you completely turn the
potentiometer once, you must connect a series resistor on the potentiometer's input side
regardless of the input voltage (see figure below).
We suggest the following sizes of potentiometers and associated series resistors:
Voltage
12 V
24 V
When using a potentiometer and 10 V input voltage as the maximum value, you must ensure
that with a connected input voltage of 24 V, 14 V must release via the series resistor so that
a maximum of 10 V are supplied when you turn the potentiometer one full rotation. With a
voltage of 12 V, this can be neglected.
Note
The LOGO! AM2 expansion module provides additional analog inputs. The LOGO! AM2
PT100 expansion module provides PT100 inputs.
Always use twisted and shielded cables for analog signals, and keep these as short as
possible.
LOGO!
Manual, 04/2011, A5E03556174-01
Potentiometer
5 kΩ
5 k Ω
LOGO! installation and wiring
2.3 Wiring LOGO!
Series Resistor
-
6.6 k Ω
51