On 1 October 2011 05:57, Kirk Wallace <[email protected]> wrote: > Thanks for all of the replies. I think I solved it by tying the input to > the control common with a resistor and capacitor as shown in the > attached file.
A "leaky bucket" filter, I think. The usual input circuit is a capacitor as shown with the resistor between the output of the PWM and the top of the cap. However that doesn't work with an opto, as 0V doesn't discharge the cap, it just doesn't charge it. I have a circuit very much like yours (with the addition of a constant-current regulator) but it turns out to be horribly non-linear except at just the right frequency. My solution (and yours too, I suspect) is to use just the right frequency. I have an idea for a way to use a second opto to discharge the cap through the same resistor during the low portion of the PWM, which should be linear at all frequencies, but have never bothered trying it. -- atp "Torque wrenches are for the obedience of fools and the guidance of wise men" ------------------------------------------------------------------------------ All of the data generated in your IT infrastructure is seriously valuable. Why? It contains a definitive record of application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-d2dcopy2 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
