Originally Posted by
TheHermit
Thank you for chiming in on this subject that is currently bewildering me. Guess I need to stop worrying about breaking non-existent torsion bars and manufacturing problems within my imagination. Your hands on experience with modern galvos trumps that, for sure.
I assumed that the differential inputs of the galvo drivers required + & - signals, otherwise there would be an offset between Gnd on one input and the signal on the other. Am I misunderstanding something?
On the other hand, I planned to use single ended 0-5VDC for RGB, as Greg has mentioned.
Thanks for your advice, Lasermaster1977. I'm seeing several different circuit designs from others, which is very confusing for the average pseudo-tekkie. Had hoped to find only one 'best' design within the community after all these years.
I'd really like to get over this hurdle and move on to completing the rest of the system.
Sorry for my late response but for some reason I've not been receiving email notifications of the additional comments on this thread.
Open or closed-loop galvo power driver outputs are usually bipolar, like an audio speaker power amp. They are usually just single ended, push-pull power drive amplifiers. At least in the old days.
To use a further audio analogy, audio line outputs can be single-ended or balanced. At audio line levels (-10 to 0dbm typically or pk-to-pk voltages levels of .7 - 1v) noise is usually not an issue when using shielded cables where cable lengths are a few feet to 25 feet.
Microphone levels are far lower (-50-60 dbm) and high quality mic pre-amps will have balanced, low-level inputs to the pre-amp for best noise immunity.
So for best noise immunity and long, line level cable runs having balanced line drivers insures good noise immunity, and any capacitive or inductive noise that is picked up while the signal is in transit is usually canceled out by the balanced line.
ILDA inputs can be either single-ended or double-ended (balanced). When the Ground of a single-ended line input signal is tied to the ILDA minus connector for either axis, the trade-off for doing so is that the scanner output swing is half what it would be compared to a double-ended or balanced line input.
My current "hobbyist" setup between the output of my XY DAC's single-ended to double-ended line level signal "mixer/modulators" sends the final line-level XY signals to the ILDA Input connector on the projector through a 10 foot long, unshielded flat ribbon cable with no problems. My RGB outputs are 0-5v single-ended just like Greg's, running through the same 25 pin flat-ribbon cable.
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Everything depends on everything else