Hello All.
I'm working on my projector wiring and have a question about the modulation signal from the DAC to the Laser Driver.
On DZ's website he has a nice diagram showing the connection's but he only shows a single positive run from the breakout board to the driver.
In Bills article he wrote he shows both positive and negative going from the DAC to the driver.
I would think that both lines coming from the FB3 through the Breakout board should go to the Driver, but I've looked at the diagrams long enough to develop doubt.
So should the negative mod signal wire go to the driver or to the central ground point (pin 25)
When I first built my RGB I had the modulation lines connected as if they where differential i.e. the + and - blanking leads connected to the + and - colour outputs of my FB3.
The projector had a weird problem where the brightness faded from the centre to the bottom of the scanned image (below the horizon).
This was corrected by connecting all of the blanking -ve connections to pin 25.
Recklessly interfering with Darwin’s natural selection process, thereby extending the life cycle of dim-witted ignorami; thus perpetuating and magnifying the danger to us all, by enabling them to breed and walk amongst us, our children and loved ones.
Thanks for the quick answer Doc
So the white wire from the laser driver is going to pin 25? (isolated grounding point)
This would be the same point that the scanner power supply ground is connected?
And if so then the signal negative from DZ's breakout board is left un connected?
Sorry for all the question, I don't won't to screw this up
It is my understanding that if you are using the central gounding point that includes the chassis protective ground; you do not connect pin 25 to this point.
My projector has a central gound point for the power connections, including the protective earth bond.
The signalconnections are connected to P25 from the ILDA connector. This is the scheme that corrected my problems.
I've read somewhere that the signal -ve connections are connected to P25 inside the FB3, but that doesn't seem to be the case with mine.
Recklessly interfering with Darwin’s natural selection process, thereby extending the life cycle of dim-witted ignorami; thus perpetuating and magnifying the danger to us all, by enabling them to breed and walk amongst us, our children and loved ones.
Thanks Doc,
My grounding point is isolated from chassis ground.
I will connect the signal ground from the Driver to the Central Grounding point which in turn is connected to the GND terminal on DZ's BOB.
So DZ's drawing is the correct way to wire this up (except for the scanner amp ground)
Recklessly interfering with Darwin’s natural selection process, thereby extending the life cycle of dim-witted ignorami; thus perpetuating and magnifying the danger to us all, by enabling them to breed and walk amongst us, our children and loved ones.
Hi Chuck, thanks for bringing this topic up, projector wiring can get very confusing at times. The only think I'd change in the drawing above is on the laser power supply where is says GND. I think that might be throwing folks off the most. I'll add that to my "to do" list to get fixed. It would be best labelled "common". Most of the power supplies I've seen label it COM, which is usually seperate from GND on the supply.
Ok, what you have here is a compairison of two seperate things. The reason why -R, -G and -B are disconnected is because the laser drivers only accept single ended signals. The only time you would use -R, -G or -B is if you had a laser driver that could handle differential. That is with one exception, I have experience with one LaserWave laser and it seems that the input might be optically isolated, not completely sure as I haven't really investigated this much further. With the LaserWave, it needed to have a common signal for the modulation input as well, in this case, if you have a red LaserWave laser, which has a single ended input, you would attach +R and -R, and set the dip switch number 3 to ON (on the breakout board), this ties -R to pin 25 on the breakout board.
For the scanners, you should always run +X/-X and +Y/-Y, and leave common (GND) disconnected on the modulation side. Since the scanner amps are already attached to common and GND on the breakout board, if you run an additional common (GND) to the modulation input you would effectively create a ground loop.
Hey Thanks DZ,
That saves me a run to the ground. So Dip Sw #4 does the same for green, and # 5 ties the blue to pin 25 as well.
I just took a close up look at the board it is labeled.
So with a RGB and using the interlock loop I would want #'s 3;4;5 and 7 on, the rest off. Nice Board, thanks!
It's not required to have them on, to be honest, most, if not all, DACs out there run single ended color output anyway. Even the QM2K's are setup for single ended output, except the older ones. And yes, #7 should be on if you don't plan on running another projector from the pass thru pin header. If you do, then you'd set #7 off and #8 on to include a slave projector in the interlock loop.
Recklessly interfering with Darwin’s natural selection process, thereby extending the life cycle of dim-witted ignorami; thus perpetuating and magnifying the danger to us all, by enabling them to breed and walk amongst us, our children and loved ones.
Question about Modulation Signal
.
Reply With Quote
(except for the scanner amp ground)
