On Tue, 29 May 2007 17:04:30 -0400, "Charles"
wrote:


"Coyoteboy" wrote in message
...
I'm looking to create a VGA fader - I have a projector that takes a VGA
signal from a PC, but I want to be able to fade that signal down to black
between projections, manually using a slider. I know there are production
items out there but they are in the region of upper hundreds and
over-spec'd for what I need. I just need to be able to fade in and out one
input.

I cant find, on a brief hunt, the VGA signal spec but I would guess its
got a sync line and 3 AC signals for pixel brightness. I hear it may be
~0.7v p-p but i dont have that confirmed. Would it be fairly simple to
create a variable gain amp to maintain 1:1 or lower gain to fade the
signals to black without losing sync with the projector (it pops up a blue
screen when the cable is unplugged). Obvioulsly one amp on each analogue
line.

I don't think you can gracefully fade a digital signal.


Standard VGA is analog, not digital.

A quick version would require a triple ganged pot, perhaps 150 ohms
each (one for each color signal). I guess three sliders with some sort
of homemade handle to gang 'em together might do just fine.