Parallell Wiring Of ILDA RGB ?

[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 !