looking for any help to make myself an RGB modulator for my video projects..

easiest way to achieve 3 sine waves 120 degrees apart. variable frequency. voltage control is a plus.

I've been going through tons of circuits this morning but not sure where to start.. seems a lot of what i find involves a static frequency.
mostly looking at low frequency speeds.. but up would like to at least hit 1Kz

-nick

 

It'd be easy to send this signal to the audio port of a computer or iPod, or any music player. I guess you want a circuit, but there are easier ways.

Someone here was just asking about the UM66 tone generator. That might work?

Hmmm.... I guess you'd need 3 discrete channels, not just the two of stereo.

 

http://www.edn.com/article/463664-Enhanced_three_phase_VCO_features_ground_referenced_outputs.php#

figure here -pdf

i've been looking at this circuit. but my recognition skills are not there apparently.

says with current values i can achieve 0.1 to 26 Hz. which i can deal with for starters
.

my issue is with IC2 and IC3. will any op amp suit this for the most part.. lately i have been dealing with LM6172's so I wouldn't mind using them.. although it could be done cheaper.

also of note. confusing... IC3D and IC3A both show pin 1. and the power supply input goes says pins 4 and 11 on IC3 and IC2.. Yet IC2 shows pin 1 as the output of the buffer into the diff amps.?

any recommendations on chips or anything is greatly appreciated.

 

Your link didn't work; I'm re-posting it using the URL feature:

http://www.edn.com/article/463664-Enhanced_three_phase_VCO_features_ground_referenced_outputs.php

I just happened to pop in and look at this; no time to do anything with it as I'm on my way out the door in a couple of minutes.

 

The devil is in the details, as usual, but here is one way to do it.
The upper Johnson counter divides by 6, and puts out 3 square wave phases separated by 120°. The switched capacitor filters each have a center frequency equal to Fclk/100. The lower Johnson counter divides the VFO output by 6, so that the ratio of Fclk to Fin is 100 at the inputs to the filters.
There are several mfrs of switched capacitor filters. Google to find them.

 

Your link didn't work; I'm re-posting it using the URL feature:

http://www.edn.com/article/463664-Enhanced_three_phase_VCO_features_ground_referenced_outputs.php

I just happened to pop in and look at this; no time to do anything with it as I'm on my way out the door in a couple of minutes.

That's an interesting circuit. The link was posted while I was creating my block diagram (post #5).
It is certainly simpler than mine, and that's an understatement.
I wonder how the "sine waves" look?

 

I wonder how the "sine waves" look?

im thinking the same.. although not a massive concern.. Truly for RGB sweeps triangle is best.

but i currently use three asynchronous oscillators on sine and it looks COOL!

hopefully i can get this circuit going.

 

im thinking the same.. although not a massive concern.. Truly for RGB sweeps triangle is best.

but i currently use three asynchronous oscillators on sine and it looks COOL!

hopefully i can get this circuit going.

Triangles should be much simpler than what I posted.

 

any big leads?