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Jeremy Blum

Jeremy is an Electrical and Computer Engineering Student at Cornell University. He has been building microcontroller projects since high school, from a prototype prosthetic hand with a novel control scheme, to a nerf gun that fires at the intruders and uploads their picture to the web.

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e14 Contributor over 15 years ago

Hi Jeremy, thanks for the great tutorials.

In the tutorial 04 analog inputs, I tried to use a microphone instead of a photo resistor to dim LED, but it doesn't work.

Could you give me an advice?

Thank you once again

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Hong
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sciguy14 over 15 years ago in reply to e14 Contributor

A microphone is a diaphragm that vibrates back and forth and generates a voltage waveform with a frequency corresponding to the pitch of the sound it received, and an amplitude proportional to the volume. So, you can't just treat it like an analog input. You'll need to use a frequency to voltage converter if you want to vary voltage based on frequency. If you want to vary voltage based on volume, put it in series with a diode to kill the negative hald of the waveform, and use a capacitor to smooth the input value. This will basically make a half-wave rectifier, which when sampled will give you an RMS voltage approximately equivlant to the volume. It's not a perfect Solution, but it should get the job done.

Half Wave Recitifiers: http://en.wikipedia.org/wiki/Rectifier#Half-wave_rectification
RMS Voltage: http://en.wikipedia.org/wiki/Root_mean_square
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simon.monk over 15 years ago in reply to sciguy14

Hong,

Microphone inserts do not produce a big enough signal to do what you want without amplification.

There is an example of a VU meter, that amplifies the sound signal from a mic in my book: http://www.arduinoevilgenius.com

Simon.
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simon.monk over 15 years ago in reply to sciguy14

Hong,

Microphone inserts do not produce a big enough signal to do what you want without amplification.

There is an example of a VU meter, that amplifies the sound signal from a mic in my book: http://www.arduinoevilgenius.com

Simon.
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