[sdiy] PWM, Vactrols & Opto-Isolators

[Tom Wiltshire]

Dustin,

I've had some success with the PWM outputs on basic PICs, so don't  
assume you *have* to use an external DAC. I've used it PWM to output  
ADSR envelopes and LFOs. Details are on my website:

http://www.electricdruid.com/

These projects use the PWM at the PICs maximum rate (for 10-bit  
output) of 19.5KHz. I used a 2-stage op-amp filter to recover the  
analog level. The surprising thing about it was actually how good the  
quality was. I was expecting something falling between "terrible" and  
"barely good enough" and in fact it's "quite good" bordering on  
"perfectly ok". There's only a very few situations in which you can  
even tell it isn't analog, which I found remarkable.

In the end, it's such a cheap, simple technique, it's got to be worth  
a shot, no?!

Regards,
Tom

On 14 Jan 2010, at 00:19, Dustin Withers wrote:

> The application is a mix of my own interest and that I've noticed many
> of these inexpensive micro controller boards have many PWM outs. I'd
> like to be able to do digital control of analog circuits. It seems my
> best bet maybe some kind of DAC though, right?
>
> dustin