At 05:53 PM 11/11/2006, dax2@hotmail.com wrote: >I need to use a 12F675 to detect an audio signal of about a volt. Any ideas? What dynamic range do you expect the audio input to cover? In other words, if the loudest part of the signal is about 1V, what is the quietest level you expect to see at the input and still have it register as audio being present? What frequencies are important to you? For example, the bass content of a song is generally louder than the mids and highs. On the other hand, speech contains little bass content. I've done a little of this: silence sensors for radio stations, beat detectors for DJ lighting systems. The silence sensors I did were all analog (this was back in the '70s & 80's); one version of DJ lighting beat detector was also all analog; the most recent uses some analog circuitry and a 12F675. One technique that worked fairly well for beat detection was band-pass filters feeding simple AGC gain controls (this was a dual detector - kick & snare). I looked at the slope of the AGC control signal - in other words, used the AGC block as a simple method of compressing the dynamic range to a very small range. Darn thing actually worked rather well. Silence sensors I built for radio broadcast were different than what I described above. They used similar techniques of looking at the slope of the AGC control voltage but that was also differentiated so that constant tone or hum would not show up as a valid audio signal. In other words, the audio had to not only be present, but also had to be changing. Timeout period was fairly long - I recall about 30 seconds or so. The above may give you some ideas. What are you trying to do? dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 22 years of Engineering Innovation (1984 - 2006) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist