4.4.3 Safe series connection
Overview
Se
veral safety switches can be connected in series in a safe series connection. The
connected devices act like a single device.
The following options are available:
•
Safe series connection with Flexi Loop (with diagnostics)
In a series connection with Flexi Loop, the safety switches are connected to Flexi
L
oop nodes. Each Flexi Loop node evaluates a safety switch and sends the infor‐
mation to the Flexi Soft safety controller.
•
S
afe series connection with T-connector (without diagnostics)
In a series connection with T-connectors, several safety switches are connected
v
ia T-connectors and connected to the safe evaluation unit.
•
S
afe series connection in control cabinet (with diagnostics)
In a series connection in the control cabinet, the safety switches are led to the
cont
rol cabinet individually. The OSSDs of the safety switches are connected in
series there and evaluated by the evaluation unit. The Aux outputs are individually
connected to the programmable logic controller (PLC).
Safe series connection with T-connectors or in the control cabinet
Do not use more than 30 safety switches in a series connection.
The maximum number of safety switches depends on the following factors:
•
Applied supply voltage
•
Length of cables used
•
Cross-section of cables used
1 1 1 1 1 2
OSSD1
OSSD2
OSSD1
OSSD2
OSSD1
OSSD2
OSSD1
OSSD2
OSSD1
OSSD2
Figure 4: Switching with 5 safety switches connected in series
1
Safety switch
2
Safe evaluation unit
The voltage drop in the series connection must be checked so that the defined mini‐
mum v
oltage is still applied to the last safety switch.
For connection cables with a length of 2 m and a cable cross-section of 0.25 mm², the
maximum number of safety switches in connected in series depends on the voltage as
follows:
PROJECT PLANNING 4
8018754/12IU/2020-01-30 | SICK O P E R A T I N G I N S T R U C T I O N S | STR1
15
Subject to change without notice
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