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Note:
• Properly interface the output signal switching devices (OSSD)
• Failure to properly interface the OSSD Outputs to the guarded machine could result in
serious injury or death.
• To ensure proper operation, the Banner device output parameters and machine input parameters
must be considered when interfacing the Banner device OSSD outputs to machine inputs. Machine
control circuitry must be designed so that the maximum load resistance value is not exceeded and
that the maximum specified OSSD Off-state voltage does not result in an On condition.
4.3.2 Connecting the FSD Interfacing
Final switching devices (FSDs) can take many forms, although 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 SX. FSDs can also be used to control an additional number of hazards by creating multiple protective stop
circuits.
Protective Stop (Safety Stop) Circuits
A protective stop allows for an orderly cessation of motion for safeguarding purposes, which results in the stopping 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 (via external device monitoring) 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 contacts to control a single hazard (if one contact fails ON, the second contact will arrest the hazard and prevent
the next cycle from occurring).
The interfacing of the protective stop circuits must be accomplished so that the safety function cannot 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 SX.
The normally open safety outputs from a safety module provide a series connection of redundant contacts that form
protective stop circuits for use in either single-channel or dual-channel control.
Dual-Channel Control
Dual-channel control provides the ability to electrically extend the safe switching point beyond the FSD contacts. With proper
monitoring, this method of interfacing is capable of detecting certain failures in the control wiring between the safety stop
circuit and the MPCEs. These failures include a short circuit of one channel to a secondary source of energy or voltage, or
the loss of the switching ability of one of the FSD outputs. Such failures could lead to the loss of redundancy — or to a
complete loss of safety, if not detected and corrected.
The possibility of a failure to the wiring increases as the physical distance between the FSD safety stop circuits and the
MPCEs increases, as the length or the routing of the interconnecting wires increases, or if the FSD safety stop circuits and
the MPCEs are located in different enclosures. For this reason, dual-channel control with EDM monitoring should be used in
any installation where the FSDs are located remotely from the MPCEs.
Single-Channel Control
Single-channel control uses a series connection of FSD contacts to form a safe switching point. After this point in the
machine’s safety-related control system, failures can occur that would result in the loss of the safety function (such as a
short-circuit to a secondary source of energy or voltage).
For this reason, single-channel control interfacing should be used only in installations where FSD safety stop circuits and the
MPCEs are mounted within the same control panel, adjacent to each other, and are directly connected to each other; or
where the possibility of such a failure can be excluded. If this cannot be achieved, then dual-channel control should be used.
Methods to exclude the possibility of these failures include, but are not limited to:
• Physically separating interconnecting control wires from each other and from secondary sources of power.
• Routing interconnecting control wires in separate conduit, runs, or channels.
• Locating all elements (modules, switches, and devices under control) within one control panel, adjacent to each
other, and directly connected with short wires.
• Properly installing multi-conductor cabling and multiple wires through strain relief fittings. (Over-tightening of a strain-
relief can cause short-circuits at that point.)
SX Safety Laser Scanner
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