SCR - Viper Safety Relays
SCR-31-i / SCR-21-i / SCR-31P-i
The new generation of safety relays from IDEM
Single or Dual channel operation
The Viper Safety Relays range from IDEM are designed to meet the latest safety standards and
offer enhanced LED diagnostics and simplified wiring. Applications include safety interlock
switches, emergency e-stop devices door guard monitoring. The SCR-31P-i is design to be
compatible with OSSD devices.(e.g. Light Curtains)
The Viper Safety Relays range includes output expansion units that can be directly wired to SCR-
21-i / SCR-31-i / SCR-31P-i safety relays to increase the number of safety output contacts. The
expansion modules are available with either immediate or time-delayed output contacts.
The SCR-21-i / SCR-31-i / SCR-31P-i internal logic uses force guided relays to achieve cross
monitoring, this ensures that a single fault does not lead to the loss of the safety function and that
all faults are detected at or before the next safety demand.
Monitored Manual or Auto Start/Reset
Up to 3 Safety output contacts
1 Auxiliary output contact
(Depending on model No.)
Contactor feedback check
Easy diagnosis of status via 6 LEDs
Up to PLe, SILCL 3, Category 4
22.5mm DIN rail mounting
24Vac/dc operation
Emergency stop and guard interlock
monitoring
Output expansion units available to
increase number of outputs.
Functional Description
When the control line inputs are closed and the start/reset condition
has been met the safety output contacts close.
The safety relay outputs open when the inputs are de-activated or if
there is a power failure. When dual channel inputs are used it is not
necessary to synchronise switching of the input channels.
When operating in the monitored manual reset configuration the
reset button must perform a make-then-break action before the
safety relay will activate.
External device feedback contacts can be monitored via the reset
loop.
Block Diagram and Connections
Terminal
Description
A1
Power Supply
A2
Power Supply
S11
24Vd.c. Control voltage
S12
Control Line
S13
Control Line (SCR-21-i / SCR-31-i only)
S14
Control Line (SCR-31P-i only)
S10
Control Line
S21
Auto Start
S22
Monitored Manual Start
13-14
Safety Output Contact 1
23-24
Safety Output Contact 2
33-34
Safety Output Contact 3 (SCR-31-i / SCR-31P-i)
41-42
31-32
Auxiliary Output Contact 1 (SCR-31-i / SCR-31P-i)
Auxiliary Output Contact 1 (SCR-21-i)
SCR-21-i / SCR-31-i
SCR-31P-i
