2022/07/28 09:15
3/26
PASS
Complete Help Docs - https://wiki.pangolin.com/
Brief Theory of Operation
Ideally the PASS circuit is installed inside the projector, rather than externally. PASS may be inserted into
the ILDA (analog signal) signal stream, or alternatively inserted into the signal stream after your own
projector electronics (such as differential color receivers or scanner invert switches) but before the
scanner servo drivers and laser modulators or drivers. Given this location within the signal path, PASS is
able to interrupt the flow of the color signals, as well as forcibly close the shutter and open the projector
Interlock circuit if necessary.
PASS monitors the following projector-health-related properties:
Scanner power supply and internal PASS power supplies
Scanner position signals to derive:
Scanning velocity
Effect size
Horizon( “Protected Area”)
PASS logic system
Beam Power during both blanked and non-blanked periods
Control Panel signals, including ESTOP and Manual Reset (optional)
Power Supply monitor and critical fault response
When power is not applied to PASS, or when PASS detects that the power supply is not sufficient to
properly operate the laser projector, PASS will crowbar (short-circuit) the color signal inputs, and forcibly
close the shutter and intensity outputs. PASS will also open the projector interlock signal path (ILDA pins
4 and 17). As long as a fast shutter is located within the beam path and as long as the interlock signal
path is used within the projector, this dual action will prevent light from being emitted from the projector
under all circumstances.
Since the shutter is closed and projector interlock are opened during critical fault conditions, these two
external elements are able to work in a redundant fashion, incase either of these were to fail individually.
Because of this, PASS requires the use of both the shutter, and projector interlock.
Scanner Position Signal monitoring
PASS monitors the X and Y position signals and derives Euclidian vector velocity as well as effect size. If
the vector velocity is found to be below the Minimum Velocity (the minimum speed that the beam is
required to sweep, in X and/or Y, in order to be considered to be safe), and found to remain there for a
period longer than the Dwell Time (the time that a beam may remain at or below the minimum velocity
see page), PASS will blank (pull to zero volts) all color signals and the intensity signal. PASS will only do
this for the period of time that the beam is below the “Minimum Velocity”. As soon as the beam speeds
back up, or the beam enters a non-protected area (i.e. above the horizon if enabled), PASS will allow the
color signals to flow from the Input to the Output. The Effect Size has a similar result, and this is included