Hello Lindy, A PWM Signal is a turning on and off of a DC voltage, in the case of a PIC, 0 to 5 volts. A coupling capacitor is used to block that DC component and pass the AC component. What you have then is a series of pulses that need smoothing to recover the modulation from the PWM pulses. This is very much like FM Radio. Using a lowpass filter blocks the carrier and passes the Modulating signal (audio) usually the carrier is many times the frequency of the modulating signal. There are many ways of creating a modulated signal, all I can say is read and ask lots of questions. If you have a chance, follow up with some schooling in electronics and computer science to gain the background knowledge to really put your ideas to work. It seems that you have lots of great ideas, and just need a knowledge database to fulfill them. Wishing your future to be full of great achievements. Vern ----- Original Message ----- From: Lindy Mayfield To: Sent: Friday, June 18, 2004 4:34 PM Subject: Re: [EE]: Beginner help in understanding circuit > > >My problem is in understanding the function those components > > >in the diagram have from the PWM output to the op-amp. > > Specifically > > >what the relationship is between the PWM coming out from the > > PIC > > >and what is going on with the resistors and caps. > > > > That network of resistors and capacitors functions as a low-pass > > filter: it takes the high-frequency PWM signal and removes the > > AC > > components (or most of them, anyway, except for a little bit of > > ripple) from it, leaving only the DC component which represents > > the average value of the PWM waveform. > > > > Dave D. > > > > > I remember LPF's and HPF's from studying about synthesizers. Like, for instance, passing a noise through it and getting a cymbal or drum sound. > > But you mention DC components. I don't understand that. What does that have to do with the DC PWM signal? Where was the AC in the mix? > > And most importantly, why or what about the PWM signal made it necessary to low-pass-filter it? What where they trying to get by it? > > Thanks for helping a learner! > > Lindy > > > --- > Outgoing mail is certified Virus Free. > Checked by AVG anti-virus system (http://www.grisoft.com). > Version: 6.0.699 / Virus Database: 456 - Release Date: 6/4/2004 > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body