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Release 7/2009 Ver. 1.0
Each LED and photodiode is fitted with a precision lens,
which produces an evenly intense, slightly diverging
beam of infra-red light from each LED and an evenly
sensitive, slightly converging 'reception cone' into each
photodiode. This arrangement provides a high signal-
to-noise ratio and maximum operating range for the
system together with ease of alignment and rejection of
extraneous reflected light sources.
The function of each LED and photodiode is controlled
by its own dedicated, specially-designed ASIC
(Application Specific Integrated Circuit). All the circuitry
necessary for the operation of an LED or photodiode is
contained within this single component, resulting in a
very
low
component
improvement in system reliability.
For each LED in the emitter unit there is a
corresponding photodiode at the same relative position
in the receiver unit. Each LED/photodiode pair makes a
'beam' and the curtain is made up of a number of such
beams, all parallel to each other. (See Figure 3.)
Figure 3
Only one LED and one photodiode are active at any
time. The emitter unit runs independently from the
receiver unit. There are no connections between the
units.
The emitter unit activates each of its LEDs in turn and
the receiver unit synchronizes with the emitter unit.
TAPESWITCH CORPORATION
100 Schmitt Boulevard
Farmingdale, New York 11735
count
and
consequent
Technical Manual: GS-120 Light Curtain Systems
Each receiver ASIC, in its turn, generates an output
signal which is proportional to the level of infra-red it
receives from its corresponding LED. Signals from
other sources, such as background lighting, are filtered
out inside the ASIC.
There is one microprocessor in the emitter unit and two
in the receiver unit. All three microprocessors perform
exhaustive checks on their own hardware and software,
prior to and during operation.
The two in the receiver unit continually communicate
their results to each other such that if a fault occurs in
one device the other can shut the system down.
In the receiver unit there are two independent switching
channels each containing an output signal switching
device (OSSD). Each of the two microcontrollers in the
receiver unit controls one of these OSSDs and monitors
the other.
The OSSDs are very robust solid state devices. These
devices are intended to be connected directly to the
machine control system, a Tapeswitch interface unit or
a suitable safety relay such that if one or both of them
are in the OFF state, the machine will go to or remain in
a safe condition, for example, by stopping dangerous
motion or by preventing dangerous motion from starting.
2.2
COMMUNICATIONS
The receiver unit incorporates a serial communications
port.
Various auxiliary Tapeswitch units can be
connected to this port for the purposes of programming
functions within the light curtain and for interrogating the
system.
No equipment other than Tapeswitch brand should be
connected to this port. Full instructions for the use of
this port with auxiliary equipment are provided within this
manual.
2.3
TEST INPUT
A pair of terminals is provided across which a pair of
normally closed, volt free contacts should be connected.
When these contacts are opened the emitter unit will
stop scanning, forcing the OSSDs to the OFF state.
This input simulates a curtain obstructed condition.
NOTE: This input is provided to allow the GS-120 to be
used with machine control systems which need to cycle
the safety circuit prior to operation. The GS-120 system
itself does not require this input to be used. If this input
is not used it should be jumpered and remain jumpered
at all times.
10
Phone: 631-630-0442
Fax: 631-630-0454
www.tapeswitch.com
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