Banner EZ-SCREEN­ Safety Light Curtain Systems - Manual (Page 36)

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 increase,
as the length or the routing of the interconnecting wires increases, or if the FSD safety stop circuits and the MPCEs are located in differ-
ent 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 can not 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.)
• Using positive-opening or direct-drive components, installed and mounted in a positive mode.
Machine Primary Control Elements
Each of the two Machine Primary Control Elements (MPCE1 and MPCE2) must be capable of immediately stopping the dangerous ma-
chine motion, irrespective of the state of the other. These two channels of machine control need not be identical, but the stop time per-
formance of the machine (Ts, used to calculate the safety distance, see
EZ-SCREEN Calculating Safety Distance on page 13) must take
into account the slower of the two channels. Some machines offer only one Primary Control Element. For such machines, it may be
necessary to duplicate the circuit of the single MPCE, by adding a second. Refer to
Generic Wiring to FSDs (manual reset) on page 41
and Generic Wiring — Interface Module (2-Channel EDM, Manual Reset) on page 42, or consult the machine manufacturer for addi-
tional information.
Manual Reset/Remote Test Input and EDM
A means is provided for the connection of an external remote test switch or contact (typically a normally open, held closed). Cycling this
switch “turns OFF” both OSSD outputs.
A single input provides the means to reset the system from a latch or lockout condition, to externally test the light screen and its interface,
and to monitor external devices (EDM) for proper operation. If the System is in Run condition with outputs ON, operating the switch
results in a test. If the System is Latched or Locked Out, operating the switch results in a reset. If this input is connected to 0V dc or left
floating, the System goes to a lockout condition on power-up. (See
Troubleshooting and Lockout Conditions on page 47 for clearing
lockouts.)
Connect the receiver’s reset/test wire (pin 8) to the supply voltage (see Generic Wiring to FSDs (manual reset) on page 41 and Generic
Wiring — Interface Module (2-Channel EDM, Manual Reset) on page 42) via the reset switch. The switch should be a normally closed
(N.C.) reset switch, or contacts of the Machine Control Test circuit (typically a normally open contact held or energized closed), or the
monitoring contacts of the external device(s) being verified. One switch could be used for the Reset and Test functions, or they can be
separate switches. However, all switches should be mounted as specified for a reset switch (see
Reset Switch Location on page 18).
EZ-SCREEN® Type 2 Light Screen Instruction Manual
36 www.bannerengineering.com - tel: 763-544-3164 122452 rev. B