Combining modulation lines

[polishedball]

What is the proper way to combine modulation line? I have some content that is RGBV I would like to tie the BV together as there is some V stuff active when no RGB is. Was thinking just using a blocking diode but that would also drop the voltages?

How could I do this so that BV both modulate my blue.

Thanks

john

[laser_freak]

What is wrong with just tying them together without any extra diodes? I ask because I am about to do something similar.

[allthatwhichis]

If you have content that uses 4 color channels you need 4 lasers and you need to separate modulation lines not combine them... Or do you just want to have your blue run on the content that is violet only?

[Badpip]

The best way would be to do it in software.

If this is out of the question, diodes could be the way to go.

Use schottky diodes with the lowest Vdrop you can get your hands on. Depending on the driver you might need a pull down resistor after the diodes.

Adjust the drivers to compensate for the lower input voltage, and set the minimum output a little higher in your software.

/Thomas

[mixedgas]

Are you trying to combine output lines from a DAC or input lines on diode drivers?

There is a electrical issue with the first, and normally no issue with the second, unless they are POOR QUALITY TTL inputs from a certain Asian marketplace.

One does not normally wish to short dac output lines together, its bad for some if not all dacs. It can easily destroy the RGB outputs on the cards.10055

Steve

[mixedgas]

In your case Polishedball, your trained well enough to build a active, lossless, rectifier circuit using opamps.

Steve

[polishedball]

In your case Polishedball, your trained well enough to build a active, lossless, rectifier circuit using opamps.

Steve

Yes was just hoping for a easy dirty way out I'll just toss it through a 741 after impedance match. Though I am thinking of adding another blue so then i'll just have to jumper for the opp scenario.

This would be 4 channels from a DAC, not possible in software as the DAC is an HD24.

John

[Badpip]

Ah, didn't realize you had experience with opamps

Do you have differetial inputs on the projector?

If not, this is a good opportunity to add it while you are at it

/Thomas

[allthatwhichis]

Can you run it through a QM and then do it in software?

[mixedgas]

Experimental should average not sum. R should be 600-1000 ohms or so for a ADAT. Gain of non-inverting opamp must be equal to number of inputs.

Steve