Using a "Y-adapter" to run two projectors
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Here are some questions regarding how to run two
projectors from one QM2000 board. If you have further questions, please
Contact Pangolin and we'll answer privately or here on the website
How do you take one LD2000 output, and run it to two different scan
amps to play the same show on two remote scan heads? I know this is done at
the conferences, even 3 heads are used sometimes. I cannot seem to find a
Y-adapter to split the DB25 cable output. Radio Shack seems to think it is
due to possible damage to either equipment. I have an A/B switching box, but
would like to know the proper way to safely do this.
Pangolin user Matt Polak replies:
I've had luck in simply splitting the connection with a standard-wired
Y-splitter in the signal cable (just solder one up) and have not run into
any major problems thus far. Mind you this was for rather short-haul
applications. (The splitter was also handy in allowing me to plug an
oscilloscope into the setup to program beam effects a little easier,
especially during daylight hours!)
On the more 'proper' way of doing
things, the simplest solution is probably a buffering op-amp circuit (built
from a few dollars of Radio Shack parts if you want to buy them locally).
Doing it this way will give you the added bonus (if you include some
potentiometers) to allow you to tweak your gain levels a bit if you ARE
going for a long-haul over cable.
Building the circuit with
adjustability (and including the color channels, not just X/Y) also helps in
allowing you to adjust the gain to your PCAOM color inputs, assuring that
the signals are all 'hitting' their 100% mark down a long cable. It's a real
pity to effectively lose laser output power due to signal loss in your
cabling for whatever reason. Also, unless your PCAOM driver is perfectly
tuned, you may not be getting absolutely 100% output potential from the
crystal even with 'proper' signal levels going in. I know I've personally
seen this, and I remember Michael Roberts also commenting a while back that
his driver liked to see more like +6v or so to bring the lines fully on.
In addition, even for standard
applications, such a box with on-the-fly adjustable gains on each of the
signal lines allows you to easily 'white-balance' the projector you're
connected to without necessarily messing around with retraining your color
palette. This is especially useful for tweaking ADAT playback and such,
where there IS no palette to adjust. (It's also pretty much necessary if
you're playing back from an ADAT without a CADAMOD
or similar)
Pangolin's Bill Benner replies:
Regarding your question of splitting the signal, Matt was
essentially correct. This technique will work fine as long as high
quality cable is used.
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Pangolin user Alberto Kellner replies:
Here is a picture using a classical output from a Pangolin LD2000 connected with two projectors. In this case, we used two 75 mW
green diode laser projectors. This also works with
multicolor lasers. We never had a problem.
(Click on the photo for a larger view.)
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Is it possible to split the serial output of the Lasershow Designer
QM2000 card to run two separate projectors simultaneously off of one card,
or will there be protocol problems? Has this been done to your knowledge?
Pangolin's Bill Benner replies:
It depends on what you mean by "serial output". Do you mean the
analog output (X, Y, colors) which controls the graphics portion of the
projector, or do you mean the DMX-512 output which can control lights, beam
projectors and other accessories?
If you are referring to the
analog graphics output, it depends on the distance that needs to be driven.
If the cables are relatively short, perhaps up to 50 feet each, and if you
use high quality cable, then you should
be able to take the analog signals and tie them to both cables. For longer
cable lengths, it is desirable to have two separate distribution amplifiers
to drive each cable segment.
If you are referring to the DMX
output, you definitely SHOULD NOT tie the output to two cables. DMX devices
usually have an "input" and an "output" connector. If
you have two devices, you connect the output of the QM2000 to the input of
the first device, then connect the output of the first device to the input
of the second device. With DMX, the total cable length can be up to 4000
feet so this generally should not be a problem.
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