Ongoing projects

I tend to start a lot of things that I never finish. The reasons I don't finish them are multifold, ranging from not having enough time, to not being able to find the requisite knowledge, to just not having the motivation to take on something too big which isn't sufficiently interesting or useful.

The projects on this page fall into the "lacking requisite knowledge" category; These are things which, for whatever reason, I haven't been able to find coherent, comprehensive instructions on the Internet or in any books or other resources; They are posted here as a simple list and perhaps a plea to other, more skilled surfers, to supply some clues to the puzzle. If anybody out there can help me with these, I'd be very thankful.

Crystal oscillator circuit

I have a simple quartz crystal oscillator circuit that works; It's on the 6502 project pages and is summarized in this picture. Although I'm happy that it works well, I would really like to understand exactly why the circuit works the way it does, and to understand the workings of crystal oscillator modules better in general. I've found countless sites that state that quartz is piezoelectric and what this means, and also a few sites that list various other circuits for using crystals, but not one that comprehensively explains how every point in the circuits work. In the simple example circuit used here on my site for the 6502 projects... What does the resistor at the top do? What does the resistor at the bottom do? And what does the capacitor do? Are they necessary? What would the circuit's output waveform look like without them? For that matter, what does a plain crystal's waveform look like without anything added to it? Does it look like a sine wave, or does it not look like anything?

VGA signals

VGA is the standard for virtually all computer monitors today, at least in the PC world. The ubiquitous 15-pin VGA connector is not as well-understood as I'd like it to be, though. Although I understand the concept of multiple sync and how it's used in VGA (a concept which I attempt to explain in this infobit), I'm still not totally clear on the three color circuits and how they fit into the picture; What does their waveform look like when they're in action? Are they simple and direct analog outputs? If the red output stays at its maximum voltage constantly, would that make the screen turn all red? Or is it necessary to implement some kind of oscillating action with them?

Ultimately, I'd like to be able to make a simple circuit that turns a VGA monitor entirely red, green, or blue, while blocking out any other colors. This shouldn't be too difficult, but I've been having trouble with it, partly because the analog signals are (according to all documentation I've seen) 0.7 volts, and I haven't found a good, reliable 0.7-volt power source yet. Does anyone have any ideas here?


If you can offer any advice or assistance with these projects, or if you have comments, questions, or whatever else on my website, by all means, please e-mail me. Thanks.

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