Banner OMNI-BEAM Series - Manual (Page 3)

OMNI-BEAM sensor heads are field-programmable for alarm output configuration and for light- or dark- operate. The
DIP switch, inside the sensor block, is accessible with the sensor block removed from the power block.
Switch #1 selects alarm output configuration. With switch #1 "on", the alarm output is normally open (i. e., conducts
with an alarm). Turning switch #1 "off" sets the alarm output to normally closed operation (i.e., output opens during
an alarm).
The normally closed mode (switch #1 "off") is recommended. This allows a system controller to recognize a sensor
power loss or an open sensor output as an alarm condition. The normally open alarm mode (switch #1 "on") should be
used when the alarm outputs of multiple OMNI-BEAMs are wired in parallel to a common alarm or alarm input.
Switch #2 selects LIGHT operate (switch #2 "off") or DARK operate (switch #2 "on"). In the LIGHT operate mode,
the OMNI-BEAM's load output will energize (after a time delay, if timing logic is employed) when the received light
level is greater than the sensing threshold (i.e., when five or more D.A.T.A. lights are illuminated). In DARK operate,
the output will energize (after a time delay, if any) when the received light level is less than the sensing threshold (i.e.,
when four or less D.A.T.A. lights are illuminated).When sensing in the retroreflective mode:
1) The DARK operate mode would be used to energize the OMNI-BEAM's output whenever an object is present,
and blocking the beam.
2) The LIGHT operate mode would be used to energize the output whenever the beam is unblocked (i.e., object missing).
Alarm and Output Programming
3
The OSBLVAGC is a low-hysteresis retroreflective sensor. Its emitted
light is returned by a retroreflector back to the receiver photoelement. An
object is sensed based on the decrease in reflected light signal at the
receiver photoelement when an object comes between the sensor and the
retroreflector. Low-hysteresis circuit design enables the sensor outputs to
switch based on relatively small changes in light signal levels, such as the
difference in received light level between a "clear object present" (or
"dark") condition and a "clear object absent" (or "light") condition.
The OSBLVAGC's special polarizing lens reduces the possibility of false
sensor response from reflections that may be returned from the object. In
the case of glass objects, light returned from the object is reflected in the
same plane as the emitted light, while the light returned by the retroreflec-
tor is rotated 90 degrees by the corner cubes in the reflector. The sensor's
polarizing filter allows only the 90-degree rotated light from the reflector
to pass through to the receiver photoelement. Sensing contrast is
determined by the amount of absorption and scattering that occurs as the
sensing beam passes twice through the glass object.
Plastic objects, due to their differing molecular structures, may rotate,
reflect, and pass light to various extents. Plastics that rotate light 90
degrees and reflect it directly back to the OSBLVAGC cannot be detected
retroreflectively because they can cause the sensor to respond falsely (or
"prox") in what should be the "dark" condition. Plastics that do not reflect
90-degree rotated light back to the sensor can be detected in the same way
as glass objects. Some trial-and-error experimentation may be required.
Contact the Banner Applications Department for assistance. NOTE: as an
alternative to the OSBLVAGC for plastic detection, consider the MINI-
BEAM Plastic Detector System (SM31EPD/SM31RPD or SMA31EPD/
SM2A31RPD), described in product data sheet P/N 03458.
Other small objects that do not entirely break the sensing beam, such
as yarn and heavy wire or thread, may also be sensed. For such objects,
take particular care to observe condition #1 (below). Use of a smaller
reflector will minimize "spillage" of reflected light around a small object.
Optimum sensor setup is a matter of achieving as much difference in
light level (optical contrast) as possible between the "object present"
(or "dark") and "object absent" (or "light") conditions. Sensing will
be most reliable when the following conditions are met (refer to Fig. 1):
1) The object blocks as much of the sensor's effective beam as
possible. The distance from the sensor to the object(s) should be small in
proportion to the distance between the object and the reflector. The object
should pass as close to the sensor's lens as possible (a distance of as little
as one inch is recommended). This helps to prevent transmitted light (that
Figure 1. Typical application:
Sensing clear bottles
on a conveyor
(plan view)
OSBLVAGC
sensor
Clear objects
(bottles)
Conveyor
Retro target
Effective beam
Theory and Setup
OSBLVAGC
Sensor Head
is distorted as it travels through the object) from reaching the reflector.
Also, position the sensor or object such that the long axis of the object will
be parallel to the vertical dividing line between the sensor lenses. When-
ever possible, the object should present its largest dimension to the sensor.
2) Sensing reliability depends upon sensing contrast; therefore, there
must be enough space between consecutive objects to establish a
strong "light" condition. If the space is smaller than the effective beam
diameter, sensing contrast will be diminished.
3) The object-to-sensor distance is held constant (e.g. the object's
position is constrained by guide rails).
4) The sensor's lens window and the retroreflector are kept clean and
properly aligned to each other. The lower the sensing contrast of the
application, the more important is a clean reflector! Also, be aware that
condensation on the reflector will reduce its efficiency. Proper sensor-
reflector alignment is discussed in Setup Procedure (below).
Before attempting to set up the OSBLVAGC, read and understand
D.A.T.A. system Description (page 2) and Measuring Excess Gain and
Contrast (page 4).
Setup Procedure
1) Select the location at which sensing will take place. Mount the sensor
in place so that it cannot be moved inadvertently. The sensing location
should conform to the requirements discussed above. (Continued p. 4.)
Programming Switch
Switch location