20ms is standard frame rate. 1-2 ms pulse 1.5 ms is center point You can usually shrink the frame and have it work fine. I wouldn't be surprised if a 10 to 12ms frame worked fine. Bob Ammerman RAm Systems ----- Original Message ----- From: "Stephen R Phillips" To: "Microcontroller discussion list - Public." Sent: Friday, December 17, 2004 12:28 PM Subject: RE: [PIC] audio servo driver PIC design help > > --- crayola@optonline.net wrote: > >> 60 updates per second is good enough for my purposes. >> > I believe it's a frame of 50 per second for it. Might want to check > this out to be sure. The standard is I believe 50 with a 15ms center > point PW but I've been wrong before :) > >> I understand, the speed of the servo is constant. I was planning >> on having it simulate a slower or faster rate by giving it a >> specified > Sic et Non, yes and no. You CAN vary the speed of the servo as well. > It's not very easy to do however. You will need a D/A convertor to do > it. To vary the speed of the servo movement you have to change the > voltage powering it. Most servo's operate with a minimum of 4V to a > maximum of 6V. They publish the speed of servo's generally at 5 and 6V > you can compute the speed constant of the servo from this. I don't > think varying the speed of the servo though will be entirely useful BUT > you could have a FAST and normal speed (IE 6V fast 5V normal) > >> distance to move from the current point, so a rate in this case >> of the number of locations it should move to to get from point A to >> point B. A loud sound might only have 1 location to move to (far >> away), were a softer sound might have 5 locations along the way that >> the >> servo is instructed to move to (closer). Since the later takes a >> longer period of time, the servo will move slower to the final >> location versus the loud sound which will move quicker. >> > This works :) > >> Oh I have no doubt that the servo is the weakest link in this >> plan, but its cheap, small, and fits well in a skull. I believe >> creating this circuit will create as realistic a mouth movement >> as possible despite the servos limitations. >> > For computing volume, I suggest first rectifying the input signal using > a bridge to get your DC offset. Then instead of using the linear > voltage use a logrythmic scale to determine your magnitude. You can > find A-law and u-law linear to logrythmic scales on the net. I suggest > you use there interpreted values. Are you planing on 8/10/12 bits of > resolution for your input sense? The other option is more complicated > that is putting a logrythmic amp in the signal path (and less useful). > You want to basically get your numbers in some sort of db scale (I > believe A-law matches this). Then you can do it by 'eye', IE observe > adjust and make it look right. > > Sounds like fun, now all you need are servo's to make the eyes move and > track using a pair of itnernet cams and you can have a nifty thing to > freak the neighbors out. ;) > > > ===== > Stephen R. Phillips was here > Please be advised what was said my be absolutely wrong, and hereby this > disclaimer follows. I reserve the right to be wrong and admit it as well. > :) > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > _______________________________________________ > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > _______________________________________________ http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist