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   alt.electronics      Electronics design, repair, worship, etc      7,706 messages   

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   Message 5,706 of 7,706   
   PeterD to All   
   Re: VGA signal fading   
   31 May 07 18:45:59   
   
   From: peter2@hipson.net   
      
   On 31 May 2007 06:13:07 -0700, CoyoteBoy    
   wrote:   
      
   >On 31 May, 13:27, PeterD  wrote:   
   >> On Thu, 31 May 2007 01:02:40 +0100, "Coyoteboy"   
   >>   
   >>   
   >>   
   >>  wrote:   
   >>   
   >> >"Charles"  wrote in message   
   >> >news:hP6dnbiX_-w8O8HbnZ2dnUVZ_o-knZ2d@comcast.com...   
   >>   
   >> >>>>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.   
   >>   
   >> >> That makes sense.   
   >>   
   >> >I'm concerned about shorting the signals to ground. I'll experiment with a   
   >> >cheap video card and see what is required to pull the signal low without a   
   >> >full short. It'd be fairly easy to set this up with a set of digital pots   
   >> >too, is my thinking, and enjoy the lack of mechanical failures (as a   
   >> >version2).   
   >>   
   >> That reply leads me to believe you have not a clue about what you are   
   >> doing. Best just buy the setup in this case. If you can't wire up a   
   >> set of potentiometers this is beyond your abilities.   
   >   
   >   
   >No, I can manage potentiometers, just worried about damaging other   
   >equipment should failure occur (shorting through the wiper while at   
   >full scale for example) - hence my original suggestion of a seperate   
   >signal amp which would be sacrificial in that instance. It was,   
   >however, ~1am while i was writing it and it didnt come out quite as I   
   >had planned it in my head so I can see why you thought that :)   
      
   I can't imagine how it would fail... High end of pot to the video   
   card, low end to ground, wiper to monitor/projector. Any failure there   
   would be rather unusual, to say the least.   
      
   That said, I've not seen any VGA outputs that won't survive some abuse   
   such as shorts. They are not high current devices... I don't think an   
   additional amplifier is worth the effort, afterall it could be the   
   failure point!   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

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