Safety Integrated - Industry - Siemens

Distributed application of laserscanner LS4-4 in Category 3
according to EN 954-1
Ex. No.
10 Automation Function
Description of the functionality
Application areas
The SIGUARD laser scanner LS4 is mainly used in order to provide
safe operation. At a predominantly horizontal alignment,
the presence of persons within the detection zone is continuously
monitored. When using LS4, access to the hazardous location
must only be possible through the detection zone. A
safe distance must be kept between detection zone and hazardous
location. The distance is calculated according to the
formulas in the specific machine related European C standards
or in the general B1 standard EN 999: 1998.
Picture of the LS4 laser scanner
Function principle of the LS4 laser scanner
The LS4 is an area scanner. It sends very short laser pulses and
measures the time until the pulse hits an object, as well as its
remission (diffuse reflection of a beam by a non-reflecting
surface) to the receiver in the LS4. The device uses this time
to calculate the distance between object and LS4. The sensor
unit within the LS4 rotates and sends/receives a laser pulse after
respectively 0.36°. A circular sector of up to 190° is
scanned in the center of which the LS4 is located.
Distributed application
In the "PROFIBUS" variant, the LS4 can be operated as safe bus
component together with non-safe standard components at
the same bus (PROFIBUS DP). This is enabled by PROFIsafe, a
functional expansion of PROFIBUS DP. For the user this makes
no difference: You connect the LS4 in the same way to the
PROFIBUS in which you are used to it from other DP slaves.
292 Functional Example No. AS-FE-I-010-V11-EN
Communication between fail-safe S7-CPU and the LS4
fail-safe S7-CPU (F-CPU) and LS4 laser scanner communicate
via PROFIBUS. Hereby the LS4 of the S7-CPU provides cyclic input
data of 1 byte length. The LS4 in return expects from the
S7-CPU cyclic output data of 1 byte length. These input and
output data can only be processed or evaluated in user program
and fail-safe STEP 7 program.
Cyclic input and output data
F-CPU
DP-Master
Cyclic
input data
DP
Cyclic
output data
LS4
DP-Slave
The name input and output data refer to the view of the DP
master:
■ Input data are read from the DP master, hence are output
data from the LS4.
■ Output data are written by the DP master, hence are control
signals for the LS4.
The integration of the cyclic input and output data into the
program code can seed in the delivered S7 example project.
Bits of the cyclic input data
Only one bit (Bit 7), which is useful for understanding the
complete functionality, is discussed here.
The bit OSSD (Bit 7) describes the fail-safe output signals of
the LS4. In case of a detection zone violation, this bit changes
from "1" to "0", which in fail-safe programs causes the actuator
to be switched off.
G_FB_XX_175