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PASS
Complete Help Docs - https://wiki.pangolin.com/
a circle or pattern projected at what is essentially the maximum power that it will ever be in the
audience.
Next, using the brightness level setting in the software, increase it a one percent past the level
determined above. For example, if the maximum safe power was determined to be 27% brightness, you
should increase the brightness level setting to around 28%. This should output a power level a bit higher
than the maximum determined in the step above.
Next, enable the light sensor by moving PASS Switch 4 to the “Light sensor is used” setting (switch
moved to the right).
Next, slowly turn the Maximum Safe Power potentiometer counterclockwise, until PASS “trips”. Basically
what you are doing in this adjustment is bringing the threshold down to the point where PASS will trip if it
detects more beam power than was determined to be safe above.
Once PASS has “tripped”, it will need to be reset, either using the Manual Reset pins on the control panel
connector, or by cycling power to the projector.
Before resetting PASS using control panel pins (or cycling power to the projector), reduce the brightness
level setting in the software back to the level determined above (for example, 27%).
Once the projector is running again, you can verify the “trip” level, by adjusting the brightness level
upward until it trips. We also recommend that you run a number of test patterns and show program
material with the brightness set to the maximum safe power determined above (i.e. 27%). If the projector
occasionally trips, then you might want to examine any filter or combiners used to “flatten” the spectral
response curve of the light detector used in your projector. If PASS trips repeatedly, you may need to
reduce the brightness level determined above (for example to 26% or so)…
Step 4: Set PASS Switch 3 to the desired position
If it is your intention for PASS to protect the entire scan field, then now would be the time to move Switch
3 “Protect entire scanfield” position (to the right). Otherwise you can simply leave the switch where it is.
Preparing to perform further measurements and adjustments
At this point you will be adjusting the velocity detector and dwell timers inside PASS. To do this, connect
a fast photodiode to an oscilloscope. The photodiode should be the amplified type, so that the
oscilloscope will show voltage as a result of light entering the detector. The Thor Labs model PDA100A is
a good choice for an amplified photodiode.
A 7mm aperture must be placed in front of the photodiode entrance aperture. This might be done by
cutting a 7mm hole in a piece of “Black Wrap” foil, and then placing this over the entrance aperture. The
7mm pupil allows the photodiode to measure the pulse width as a scanning beam crosses a 7mm dilated
pupil.
The photodiode should be placed on a tripod, so that it can be moved into the beam path to perform
safety-related measurements.