Pangolin FB4 Series, User Manual

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Appendix B Making The Right Connections 29

A key-switch is required for laser projectors because, under the wrong
circumstances, laser projectors could be hazardous, and should be used only by
trained laser operators. To prevent untrained personnel from operating the laser, a
key-switch is used. The key should only be given to the trained laser operator.

If the projector covers could be easily opened or removed by a user or operator, the
laser projector is required to have a
cover interlock , which will prevent the lasers
from operating when the cover is opened. This cover interlock is ideally
implemented as two spring-loaded switches connected in series with the general
projector interlock loop described above. Two switches are used instead of one, to
provide redundancy in this safety feature.

Some governments may require an additional connector to be placed on the
projector called an
external interlock connector . Electrically, this connector only
needs to have two pins, and this is connected in series with the general projector
interlock loop. One example of how this connector might be used is when the laser
projector is only supposed to project a certain effect (such as a cone shape), at only
a certain time (such as, when a performer is in just the right place that the cone will
surround them). The external interlock can be connected to a “pressure pad” that is
only active when the performer is standing in place.

A time delay is used so that, when the projector is turned on, it won’t start
emitting laser light right away. This is in place so that the laser operator can turn
on the laser projector, and then advise others who might be in the room that the
laser is coming on. The time delay allows the laser operator and others to take their
place to avoid accidental exposure to the laser. Of course, this assumes that
exposure would be harmful in the first place, which isn’t always the case.
Nevertheless, the US and other countries require a time delay to be a part of the
projector. The time delay is normally set for 20 to 30 seconds.

A manual reset is required so that if power is interrupted from the laser projector,
and then power is restored at some point in the future, the laser projector will not
automatically start outputting light until some manual intervention takes place
(such as pressing a button, or cycling the position of the key-switch). The manual
reset provides an additional level of safety.
Consider this scenario: a laser projector is operating in a nightclub, but at some
point, the power to the entire night club goes out. Then everybody leaves because
there is no power. Some time later the power comes back on. If the laser also
comes back on and emits a non-moving beam, and if this non-moving beam is
parked onto dark fabric, it could start a fire. Because of factors such as this, the
manual reset is required by certain countries.
The key-switch, cover interlock and external interlock are all easily