Audio Triggers a Relay Switch


message: Hello there i am just wondering how i would go about trying to get a circuit designed?

The situation i have is i have got a sound signal peak voltage at approx 0.3v. I require this to trigger a switching device such as a relay. There is a 12 volt DC supply available to power up any components.

If you could either send me in the right direction or if possible quote price on having this circuit designed and possibly made it will i will be most grateful.

Thank you CD from UK in 2008

Here are some circuits in the web – Voice operated relay or switch, Clap switch, Sound operated light switch … all these mean the same. A condenser microphone, pre-amplifier, rectifier, comparator and relay in that sequence. If is the first hobby project for learning home automation and the idea as old as the 70s. It was used in Toys and Lights extensively, when the fad was still on. It is still an excellent learning project that will make an new enthusiast more familiar with components. Avoid using ICs so that your fundamentals become strong.

Using ICs are like ready to cook and serve food packets. Cooking your own meal is similar to … Using Transistors and discrete components like diodes, zeners, resistors and capacitors. This will strengthen your foundation. Winding your own coils is another thing you have to learn, if you want to be a ace Ham Radio Operator.


Audio Signal Detector Switch – This circuit will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal. It could be used to turn on a relay, routing the signal to were it is needed.

Design of a Clap Activated Switch – This involves the design of various sages consisting of the pickup transducer, low frequency, audio low power and low noise amplifier, timer, bistable and switches. It also consists of special network components to prevent false triggering and ensure desired performance objectives.




Product Design - Industrial Automation and Instrumentation.

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