Banner EZ-SCREEN­ Safety Light Curtain Systems - Manual (Page 35)

WARNING: Interfacing of Both OSSDs
Both of the OSSD (Output Signal Switching Device) outputs must be connected to the machine control so
that the machine’s safety-related control system interrupts the circuit to the machine primary control ele-
ment(s), resulting in a non-hazardous condition.
Never wire an intermediate device(s) (e.g., PLC, PES, or PC) that can fail in such a manner that there is
the loss of the safety stop command, OR in such a manner that the safety function can be suspended,
overridden, or defeated, unless accomplished with the same or greater degree of safety.
WARNING: OSSD Interfacing
To ensure proper operation, the EZ-SCREEN Type 2 output parameters and machine input parameters
must be considered when interfacing the EZ-SCREEN Type 2 OSSD outputs to machine inputs.
Machine control circuitry must be designed so that the maximum open ground leakage current must not
result in an ON condition.
Failure to properly interface the Safety Outputs to the guarded machine could result in serious
bodily injury or death.
FSD Interfacing Connections
FSDs (Final Switching Devices) can take many forms, though the most common are forced-guided, mechanically linked relays or an
interface module. The mechanical linkage between the contacts allows the device to be monitored by the External Device Monitoring
circuit for certain failures.
Depending on the application, the use of FSDs can facilitate controlling voltage and current that differs from the OSSD outputs of the EZ-
SCREEN Type 2. FSDs can also be used to control an additional number of hazards by creating multiple safety stop circuits.
Protective Stop (Safety Stop) Circuits
A protective stop (safety stop) allows for an orderly cessation of motion for safeguarding purposes, which results in a stop of motion and
removal of power from the MPCEs (assuming this does not create additional hazards). A protective stop circuit typically comprises a
minimum of two normally open (N.O.) contacts from forced-guided, mechanically linked relays, which are monitored (through Power Mon-
itoring) to detect certain failures in order to prevent the loss of the safety function. Such a circuit can be described as a “safe switching
point.” Typically, protective stop circuits are either single-channel, which is a series connection of at least two N.O. contacts; or dual-
channel, which is a separate connection of two N.O. contacts. In either method, the safety function relies on the use of redundant con-
tacts to control a single hazard (if one contact fails ON, the second contact will arrest the hazard and prevent the next cycle from occur-
ring). See
EZ-SCREEN Generic FSDs Wiring on page 41.
The interfacing of the protective stop circuits must be accomplished so that the safety function can not be suspended, overridden, or
defeated, unless accomplished in a manner at the same or greater degree of safety as the machine’s safety related control system that
includes the EZ-SCREEN Type 2.
The normally open safety outputs from an interface module provide a series connection of redundant contacts that form protective stop
circuits for use in either single-channel or dual-channel control. See
Generic Wiring — Interface Module (2-Channel EDM, Manual Reset)
on page 42.
EZ-SCREEN® Type 2 Light Screen Instruction Manual
122452 rev. B www.bannerengineering.com - tel: 763-544-3164 35