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Sound Operated / Sound Activated Circuits
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Last Updated on: Thursday, April 07, 2016 01:01 PM

Circuits Designed by Dave Johnson, P.E. :
  • Audio Activated Switch
    Drawing only 2uA from a 3v lithium battery, this circuit will turn on a transistor switch, whenever it detects an audio signal greater than 0.035v RMS.

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:
Add voice command to virtual instrumentation -  30-May-02 Issue of EDN  Debates still persist in the engineering community about the relative merits of analog and digital controls of instrumentation. Meanwhile, a revolutionary new type of control—voice-command control—is gaining acceptance in many application areas (Reference 1].  This Design Idea focuses on the practical implementation of the Voice Commander voice-command interface in a virtual-instrume.... [Design Idea by Alexander Bell, Infosoft International Inc, Rego Park, NY]
Add voice commands to your CAD system -  2-May-02 Issue of EDN  The first time I activated the Language Bar (Speech Tools] in my Microsoft Word 2002 and started dictating this Design Idea, the on-screen title displayed "cat" instead of "CAD." By using the "Add/Delete Words" feature, I've trained the system to recognize the "CAD" acronym.  This was my first experience with the MOSR (Microsoft Office Speech Recognition] tool, which is part of the latest Micros.... [Design Idea by Alexander Bell, Infosoft International, Rego Park, NY]
Audio Activated Switch -  This switch circuit is powered for years by a single 3v lithium cell.  Its transistor switch closes whenever the circuit detects audio signals in excess of 50mv RMS.  It can be used to trigger relays or activate indicator lights.  (added 12/04) …. [Designed by David A. Johnson]

Audio Controlled Christmas Lights -  Here is a simple circuit to control 110VAC things such as Christmas Lights with low voltage audio. Be careful, high voltage AC can kill you.  “The basic Idea was to have Christmas lights flash with the music. In my design I use an ordinary Amplified computer speaker, a diode bridge, and a ‘CRYDOM’ SSR (Solid State Relay). In order to increase the time that the lights were on as well as protect the SSR I used a Diode Bridge to rectify the signal from the Amplifier circuit.”....(added 02/09)
Clap Activated Remote -  (circuit / schematic design added 11/06)
Clap Relay -  Clap sensitive on-off Relay.  3V Battery operated, small portable unit, (added 03/05) 
Clap Switch -  Circuit / schematic (added 02/05)
Deer Repellent (techlib) -  Here is a simple sensor which can detect the seismic vibrations caused by a person or large animal walking nearby. A representative application for the sensor is a deer repellent for the vegetable garden…..(added 02/05)
Dog Whistle -  It's well known that many animals are particularly sensitive to high-frequency sounds that humans can't hear. Many commercial pest repellers based on this principle are available, most of them operating in the range of 30 to 50 kHz. From what I've read, dogs and other mammals of similar size behave much differently than insects....(added 11/05)
Hand Clap Electronic Control -  We have all seen the commercial on TV....CLAP, ON, CLAP, OFF, THE, CLAPPER....well here is a circuit that will perform that same function… [Randy Linscott]
Hand clap lamp control -  Hand Clap Lamp/Appliance Control - Clap once for ON and twice for OFF I think [Reverse engineered schematic by Stepan Novotill]
Perimeter Monitor -  Using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned, for example, at the bottom of a garden or garage, and used to detect all sound in that area. The cable can be buried in a hosepipe or duct and is concealed out of sight. The mic is an ordinary dynamic mic insert.... [Circuit design by Andy Collison]

Sound Operated / Sound Activated Circuits#'s - P     Q - T      U - Z

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