[sdiy] PWM, Vactrols & Opto-Isolators

[Tom Wiltshire]

Dustin,

If you're looking to get a DC level out, then I'd say, yes, 30KHz is  
high. You could set the RC filter frequency for 10Hz and the pulses  
would be more than 3 decades above the cutoff, which ought to give a  
decent filtering action even with such a simple layout.

Jay's comment's about linearity are very pertinent though. PWM->LED  
linearity isn't going to be perfect, and LED->LDR linearity will add  
it's own twist too. How accurate do you need it? What's the application?

Regards,
Tom


On 13 Jan 2010, at 19:03, Dustin Withers wrote:

> Tom,
>
> Is a pulse frequency of 30Khz considered high?
>
> Thanks for the help,
> -dustin