Audio Detector Circuit
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Audio Detector Circuit as PDF for free.
More details
- Words: 285
- Pages: 3
Audio Detector Circuit [Editors note: I grabbed this off our list server. This was too good to pass up. The Trinity Firefighting Contest uses a small piezo speaker to generate a tone that emulates a fire alarm. The following email answers a requst for a circuit that will detect that sound.] Editors Second Note: Larry was kind enough to provide a better writeup of this article. Check out his article in the May 2000 Issue ----- Original Message ----From: Larry Barello To: SRS Mailing List <[email protected]> Sent: Monday, March 06, 2000 12:21 PM Subject: SRS: Audio Detector for FireFighting Someone asked, a couple weeks ago, for a circuit to do audio detection. This is what I used. Here is one that uses a single IC (LM324 quad op amp) and a handful of parts. This circuit is for detecting one of those 3.6khz (approx) beepers from Radio Shack.
A few notes: 1. the capacitor and resistor on the output of the peak detector are selected to give a reasonable decay time. I.e. so a single pulse doesn't stretch out and be miss-interpreted as an audio signal. I think I sample
the output at 100ms intervals and signal a valid sound if three consecutive samples are true. 2. the only critical parts are the trimmer, capacitors and the 560 ohm resistor in the band pass filter. The diode is not critical: any small diode will do fine. 3. The trimmer is used to set the center frequency. I just run the beeper and adjust for the strongest output signal. 4. It uses a condenser mic, surplus. Probably any computer microphone will do. The 4.7K resistor is a typical load for those things. Larry Barello http://www.barello.net
A few notes: 1. the capacitor and resistor on the output of the peak detector are selected to give a reasonable decay time. I.e. so a single pulse doesn't stretch out and be miss-interpreted as an audio signal. I think I sample
the output at 100ms intervals and signal a valid sound if three consecutive samples are true. 2. the only critical parts are the trimmer, capacitors and the 560 ohm resistor in the band pass filter. The diode is not critical: any small diode will do fine. 3. The trimmer is used to set the center frequency. I just run the beeper and adjust for the strongest output signal. 4. It uses a condenser mic, surplus. Probably any computer microphone will do. The 4.7K resistor is a typical load for those things. Larry Barello http://www.barello.net
Related Documents
Audio Detector Circuit
June 2020 7
Audio Circuit
May 2020 9
Novel Quantum Theory Detector Circuit
December 2019 17
Detector
June 2020 34
Audio
December 2019 49