Label Stop Sensor - Intermec EasyCoder PX4i Service Manual

Chapter 8 — Print Unit

8.5 Label Stop Sensor

Description
Working Principles
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The label stop sensor (LSS) controls the media feed and consists of a slid-
ing carriage on which two photoelectric sensors are fi tted. Both sensors
are identical and contain one light-emitting diode and one light-sensitive
receiver. The distance from the light path between the two parts of the LSS
to the dot line on the printhead is 46.3 mm (1.82 inches). The sensors can
be moved up to 50 mm (1.97 inches) out from the inner edge of the media
path using a screw protruding through the lower outer gable of the print
unit. In EasyCoder PX6i, this screw is only accessible when the locking
handle is folded down. The label stop sensor is hidden inside the print
mechanism and covered by two plastic guide plates, which can be removed
for cleaning.
The label stop sensor serves a number of purposes, depending on how the
printer is set up in regard of media type in Fingerprint and IPL respec-
tively:
Label (w gaps)/Gap
A beam of light is emitted from the diode in the lower part and received
by the sensor in the upper part. The fi rmware detects the front of each
label, that is, when the light is completely interrupted by the opaque
label, as opposed to the semi-transparent liner in the gaps between labels.
If no label has been detected during a media feed corresponding to more
than 150% of the set label length, a "next-label-not-found" condition is
assumed. If a renewed print operation gives the same result, an "out-of-
paper" condition is assumed.
Ticket (w mark)/Mark
Normally, a beam of light is emitted from the diode in the lower part. The
beam is refl ected back to the sensor in the lower part by the white media,
or is absorbed by a black mark. The fi rmware detects when the front edge
of a black mark passes the sensor, that is, when light starts to be absorbed.
If no mark has been detected during a media feed corresponding to more
than 150% of the set ticket length, a "next-label-not-found" condition is
assumed. If a renewed print operation gives the same result, an "out-of-
paper" condition is assumed.
By switching the cables from the upper and lower part of the LSS on the
CPU board, black marks on top of the media can be detected.
Ticket (w gaps)/Gap
The light is emitted from the diode in the lower part and received by the
sensor in the upper part. The light will either pass uninterrupted through
a detection gap in the media or be blocked by the non-transparent ticket.
The fi rmware detects the rear edges of detection gaps, that is, when the
light starts being interrupted. If no ticket has been detected during a media
feed corresponding to more than 150% of the set ticket length, a "next-
label-not-found" condition is assumed. If a renewed print operation gives
the same result, an "out-of-paper" condition is assumed.
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