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[Reply #15 on:]

I play guitar so that helps me understand what you are getting at. You've got some sort of voltage-controlled analog effect box circuit that you'd like to put under digital Arduino control by using PWM and an R/C filter to generate the control voltage for the effect. I've thought of that before, and it would seem to be fine in theory (if your circuit is happy with 0-5V for your analog control, and doesn't take too much current); otherwise as mentioned you'll want an op amp to get a different range.

Yes, certainly that is a viable application. And even the 0-5 vdc restriction is easy to overcome with simple op-amp with the gain set to whatever DC voltage range desired after the R/C filtering is done.

Lefty

[Reply #16 on:]

It's a simple oscillator circuit I have to re-dig-up. It used a resistor and capacitor and a pot to control the tone, could have added volume control. I could replace the pot with a transistor couldn't I?  As a valve?

Finished reading the Simple filter piece.

Increase in C lowers both Xc and F,  
Increase in F lowers Xc and RC

And I think that making Xc small compared to R is desired.
So that lets low frequencies pass hence the moniker.

Suppose I want to change the duty cycle of the PWM from 10% to 90% smoothly in 1/100th or 1/1000th of a second? Would this filter have trouble following that? Again: the audio frequency is generated on a different circuit, *not* the PWM frequency being converted to analog DC to control a transistor.

[Reply #17 on:]

PWM driven led coupled with a 'slow' photocell?

THANK YOU! You made my day!

[Reply #18 on:]

If you want to use PWM for clean audio, I suggest you reprogram the registers to crank the PWM frequency up. It will make filtering ALOT easier while keeping the audio intact.

Code:

TCCR1B = TCCR1B & 0b11111000 | 2;[/quote]
Will bring the PWM frequency on pins 9 and 10 to about 3.9KHz.

[Reply #19 on:]

If you want to use PWM for clean audio, I suggest you reprogram the registers to crank the PWM frequency up. It will make filtering ALOT easier while keeping the audio intact.

Code:

TCCR1B = TCCR1B & 0b11111000 | 2;[/quote]
Will bring the PWM frequency on pins 9 and 10 to about 3.9KHz.

I have an AC oscillator making the wave. Not using PWM frequency for the wave. Wanting to use PWM to affect the external sound circuit in two ways, maybe find a third.

It's like being able to control the slide of a trombone when something -else- vibrates the air.
I'm trying to control the slide with PWM, not vibrate the air, move the bow not be the string.
And I wonder how fast I'll be able to move the bow smoothly.