Re: [stella] Krokodile Cart prototype review

Subject: Re: [stella] Krokodile Cart prototype review
From: Pete Rittwage <peter@xxxxxxxxxxxx>
Date: Sat, 28 Feb 2004 09:40:46 -0500
What happens if you use a heavier-duty power supply, like 1000mA?

Chris Wilkson wrote:

The composite sync line does just what you describe here: if the voltage
level is too high, it mixes signals from the CPU into the video picture.

Weird... Can you explain "Why?" to someone like me?

Hi Thomas,

I'm not sure what Oliver means by "voltage level is too high", but I've
I've explained the mechanism below.

See my previous post for the general idea. A little more thorough here...

Every time a digital signal switches state, it draws current from the 5v
power supply.  The voltage will dip, sometimes significantly.  Because the
video section uses that same power supply it is affected by the digital
switching noise.  The video signal is basically a variable fraction of the
5v power supply.  Any changes in the power supply voltage will be directly
copied to the video signal and therefore to the tv screen.

Hope this helps!


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Pete Rittwage
Augusta, GA, USA
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