Parallell Wiring Of ILDA RGB ?

[liteworx]

Hi Quick question !

I have Quickshow with FB3, 1 x 532n 1200mw 40k System & 1 x RGB 1200mw 40 K System, I want to run both these units off of the FB3, Is it possible to parallell wire the R,G,B Output connectors on the ILDA board ? i.e. connect my modulation + to the R+,G+,B+ and my - to the R-,G-,B- ?? so if this worked it would allow me to output a full colour show from quickshow to the RGB System and the Green System would display the full image and not blackout on all colours other than green ?

[taggalucci]

Depends how your green only projector responds to an RGB signal. You can parallel wire two projectors, sure.

If your green only projector only responds to the G channel, then you can create a 4 colour palette, have standard RGB on the first 3 and set channel 4 to all 3 colours. Then just wire the 4th channel to your G channel of the green only projector.

[taggalucci]

Actually... parallel wire independently, not bridging the RGB channels. This will cause problems for you RGB projector as the colour signals would be merged. Better to parallel wire independently as standard.

Use my 4 channel colour palette suggestion.

[slicklasers]

Just wire your green projector to the intensity line...
pin 3+ pin 16-

[taggalucci]

Just wire your green projector to the intensity line...
pin 3+ pin 16-

Hey Slick, can you confirm if the intensity channel is analogue or TTL on the FB3?

[dave]

Afaik, the intensity is ttl

[liteworx]

Cool, thanks for the replies guys, I think I'll go with using the intensity channel to control my green laser (its TTL mod anyway) so this should work just fine,

Out of interest though, taggaluci could you explain further your 4ch colour pallette suggestion, cant get my head around what you mean ?

[taggalucci]

Well the 4th channel option is only really useful if your single-colour laser is analogue modulated. But...

As you can't electrically bridge R, G and B to provide a summed signal to a single-colour laser without affecting the RGB laser (which would lose it's independent colour control if you did), what you can do is sum the RGB in software and provide that to the 4th colour channel on your DAC (provided your DAC supports more than 3 colour channels and your software supports custom colour palettes, which I believe QS2 and the FB3-QS do).

So you create a custom palette and run red only to the R channel, green only to G, blue only to B, but on the 4th channel, you adjust the parameters in the palette control to send red, green and blue to it (effectively the sum of all 3 colours). This way, regardless of whether your show is showing a red only component or a blue only component, your RGB will display the correct colour, and your green laser will also project at the same time.

But as your green is TTL, this is a completely pointless thing to do and the intensity channel is designed specifically for this purpose.

[liteworx]

Ah is see now ! thanks for the explanation !

[LaNeK779]

As you can't electrically bridge R, G and B to provide a summed signal to a single-colour laser without affecting the RGB laser (which would lose it's independent colour control if you did)

maybe a stupid queation, but can't we electrically bridge R, G and B inside the single colour projector using diodes, thus not affecting the rgb laser?

[Xytrell]

Maybe, but diodes drop 0.7V, so the green would never get above 4.3V.

[Stoney3K]

Maybe, but diodes drop 0.7V, so the green would never get above 4.3V.

It would be a lot more elegant just to build a 3x3 summing matrix circuit with a few op-amps and potmeters. That way you can colour correct each projector independently in a KISS fashion.

[dave]

A opamp summer isn't going to be that elegant when all colours are at 5v, and the output of the summer is 15V..

[Stoney3K]

A opamp summer isn't going to be that elegant when all colours are at 5v, and the output of the summer is 15V..

Ever thought of reducing gain?

You can't expect something like that to work 'on the fly', since mixing multiple 0-5V signals together into a SINGLE 0-5V signal requires some mixing ratio to start with. That's not a property of an op-amp, but simple mathematics.

Using diodes is pretty much the same as using an op-amp summer with 1:1:1 ratios, as the current from all color channels will flow together and cause a voltage in the load resistance (inside the laser driver) which may become bigger than 5V if the inputs are too high, or clip at the highest input voltage possible (4,3V).

If you know the characteristics of your output and input signals (e.g. the input is always UNCORRECTED ILDA RGB) you can easily determine the ratio you need for a single or two-colour projector or for an RGB with different power ratios than perfectly balanced white. Set these in the summing matrix, and you're good to go.

Still keep in mind that what you do, R+G+B will probably determine your intensity for a single color projector, or colour levels will clip. The reason for this is because you're mixing signals together and the projector can't magically determine that you want your green-only frame to be just as bright as a full white frame. You could get around this with something that does RGB -> HSV colour conversion (or make sensible use of the Intensity channel!) or you will have to make compromises.

The same applies to audio mixers as well, although it's harder to notice. If you put up 2 equally loud channels on a mixing desk and mix them together on the same bus, you'll have a sum signal that's 6dB louder (twice as strong, voltage-wise) than the two inputs individually. The difference is that our hearing is not linear (so it won't experience the 6dB as 'twice as loud'), but our vision is a lot more sensitive to linear changes in intensity!

[hobbybob]

I mixed in all the colors using the diodes suggestions. Must admit, since i re-worked my projector today it outputs a lot more now, with the diodes removed, but alas, it worked and i thank Rob for the suggestion. But it has worked flawlessly for many shows.

[liteworx]

Quick update, I modified the wiring of my ilda cat5 cable to modulate my 532nm using the Intensity channel, although when I did this I was getting some weird cancellation issues
so I used the Intensity + and Green - as opposed to the Intensity - and this worked out fine and is a good quick fix before I bite the bullet and purchase another FB3 !