Pinnacle Systems SLT Series - Manual (Page 9)

1
Overview
SLT Series
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The SLT Series system is a dual redundant digit al
infrared point of operation guarding device which will
provide a signal to stop the machine when there is entry
into the guarded area. The system uses invisible infrared
light to detect obstructions protruding through the
guarded area. The use of infrared light provides an
unobstructed view of the work area and also makes the
SLT Series system insensitive to almost all ambient light
conditions.
The dual redundant system basically incorporates two
microprocessors, four watchdog timers, and two
separate captive contact relays to assure fail-safe
operation. If either microprocessor detects a failure in
the system or the other microprocessor , the working
microprocessor can shut down the unit. The watchdog
timers assures that if the oscillator on either
microprocessor is not running correctly, they can shut
the system down. The special
force-guided contact
relays*
allow self-checking software to detect a faulty
relay and shut down the unit with the redundant relay .
The Diagnostics Display allows the user to better
understand the current condition of the light curtain. If a
fault is discovered by the light curtain, it will be displayed.
The display is also used when options like the Floating
Blank or Auto Blank are being used. A brief description
of each follows:
The
Floating Blank
option allows work pieces
(designated by dimensions) to move throughout
the guarded area without shutting the machine
down but entry into the protected area by the
operator will still provide a signal to stop the
machine. The Floating Blank option does not need
to be adjusted for various positions or die height
changes, only adjusted for the size of the work
piece. Up to three beams at a time are allowed
to be obstructed when the Floating Blank option
is in use.
The
Auto Blank
option allows work pieces or fixed
objects to penetrate the guarded area without
shutting the machine down. The size and location
of the object(s) is automatically programmed into
the computer with a turn of a key, so you do not
need to know the size of the object to program
the unit. Auto Blank must be reprogrammed when
there is a loss of power. Up to eight beams at a
time are allowed to be obstructed when the Auto
Blanking option is in use.
The SLT Series system operates from two pylons. Power
must be supplied separately to both pylons using
standard wiring procedures. The interface or stop circuit
interconnection is made from the Receiver Pylon.
The SLT Series system can only be used on p art
revolution or clutched machines which can be signaled
to stop at any part of their cycle by opening an electrical
circuit.
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The SLT Series system is an infrared light curt ain
consisting of two pylons that talk to each other via an
infrared channel called the Sync Channel. The Receiver
Pylon transmits to the Emitter Pylon for the purpose of
synchronizing the two units eliminating the need for a
third box with a cable connecting the pylons together .
The status of the Sync Channel can be determined by
the Diagnostics Display on the Receiver Pylon which
will show flashing decimal points to indicate that the
Emitter Pylon is not firing.
The Receiver Pylon is the controller and the Emitter
Pylon is slaved to it by the Sync Channel. The internal
logic of the Receiver Pylon controls the scanning
function, the detection, the output control, and the
internal diagnostic functions.
When the two pylons are synchronized, the Emitter Pylon
begins to scan from the top down with its infrared
emitters called “data channels” or otherwise known as
infrared beams. The Emitter Pylon’s beams are scanned
many thousands of times a second and, each time a
beam is selected, its infrared emitter is pulsed. This
sequential scan of infrared pulses is picked up by the
Receiver Pylon which is synchronized to the scanning
Emitter Pylon and recorded. If a beam is blocked by an
obstruction, the control logic drops out the Output Relays
and turns on the RED indicator.
The Internal Diagnostic Logic runs at the same frequency
as the scan frequency so all operational components
and timings are checked many thousands of times a
second to insure Fail-Safe operation. The control logic
in this unit has no lock-up or failed mode except for hard
internal failures. No matter what conditions prevail, the
unit is trying to keep all systems operational.
* Force-Guided Contact Relays are mechanically linked together
to force both poles to maintain the same position regardless of
whether the relay is energized or de-energized. This allows a
welded contact to be detected by monitoring the other pole.