Hi... I am new to pics, but have been using Servo's in my RC Airplanes for years. If you are planning on using a "regular" hobby servo for the Jaw then I imagine you will hit some snags with resolution. Essentially, the servo protocol is a PWM signal with only 60 pulses per second. While adequate for flying planes, it would strike me as being somewhat limited for yur jaw. Hmmm... it might be enough, but only just. Remember that the duration of the pulse in the signal only indicates where the servo should move to, and not how fast it should move. To change the servo speed you will possible have to mess with the voltage on the line, or alternatively spend a number of servo cycles indicating progressive steps. Finally, even the fastest of servos can only rotate 60degrees in about 0.1 of a second, which may limit you in other ways. You may want to see http://www.futaba-rc.com/servos/digitalservos.pdf Anyways, I am thinking that your limitation will be with the servo rather than with the sampling rates and signal levels of the audio. Rolf cdb wrote: >--- Original Message --- >From: "Michael Cunningham" >To: >Cc: >Sent: Fri, 17 Dec 2004 00:57:14 -0500 >Subject: audio servo driver PIC design help > >:: I breadboarded the design ya'll helped me >:: >:: with previously and everything works perfectly! >:: Thankyou!.. Now on to my next challenge.. it is >:: stretching my mental capacities so far and should give >:: me experience with the a/d converter if it can work >:: like I think it might. This is a hobby circuit.. nothing >:: professional here. >:: >:: I have a servo mounted in a fake skull that can move >:: the skull's jaw. There are several non PIC based circuits out there >:: now to do this but they are simple threshold circuits. >:: If the circuit detects an audio signal it tells the servo >:: to move as rapidly as possible to open the jaw until sound >:: is not detected and it closes the jaw as rapidly as possible. >:: While this works..its not very realistic. Its doesn't account >:: for the fact that a loud sound should open the jaw faster >:: and in turn, further then a softer sound. >:: >:: It seems that a PIC with an a/d converter and ability to drive a >:: servo using PWM could be a good solution to this. >:: >:: Basically what I want to do is sample a line level audio >:: signal pretty rapidly and based on the presence of sound >:: move the servo to open the jaw at a rate based on the >:: amplitude of the sound, so a louder sound will cause the servo >:: to move quicker to a location and hence further then a >:: softer sound which will cause the servo to move slower and less >:: distance then the louder sound. So if it screams it will rapidly >:: move the jaw open, and a whisper will just cause a tiny jaw >:: movement >:: despite the duration of the sound. >:: >:: After doing some basic research on the net it looks like I will >:: need to use some circuitry to cleanup the audio signal since >:: the a/d converter bases its comparisons on 0 to Vdd and as I >:: understand it, audio signals aren't 0 to 5 volts. >:: >:: Any ideas how I can do what I want to do? I know this project >:: is probably over my skill level, but ya don't learn unless you >:: push yourself. How would you do it? I don't think the actual >:: circuit is the big issue (except for the audio cleanup part - no >:: clue there) since there are plenty of examples of driving servos >:: with PICS on the net. My biggest hurdle is using the a/d converter >:: to figure out if sound is present and the amplitude of it and >:: creating a direction and rate at which to move the servo. >:: >:: Thanks, >:: Mike >:: >:: >:: _______________________________________________ >:: 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