# Whistle Switch/Clap Switch circuit

Discussion in 'Homework Help' started by Sbuda, Oct 12, 2017.

1. ### SbudaNew Member

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Hi people.

Can you help me with building a circuit with an LED that turns ON when you whistle, and OFF when you whistle again. It's a school project. It's should have the high pass and low pass filters.

I am supposed to measure the frequency on the microphone and an amplitude by whistling, then choose choose the capacitor values for the filters and calculate the gain and the resistor values.

For now I have measured the the frequency to be 2,016 kHz and amplitude to be 208 mV.

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2. ### SbudaNew Member

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Please note: I have uploaded the block diagram and the circuit diagram as given the teacher, but i will accept any other way as long as it has got the filters.

3. ### AnalogKidWell-Known Member

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Looks good so far, although the images you posted are upside down and sideways. 2 kHz is awfully high for a human whistle; are you sure about that measurement?

What have you been taught about single-pole filters, corner frequencies, etc?

ak

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5. ### audioguruWell-Known MemberMost Helpful Member

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The filters are so simple (first order) that they are almost useless. You need third order filters or better.
Usually the output level from a microphone is very low and is amplified before being filtered.
Your "precision" rectifier is not precision because it has a diode voltage drop. The rectifier diode must be inside the negative feedback loop of the opamp to cancel the diode's voltage drop.

6. ### magvitronActive Member

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Hello Sbuda,
The method is good just as an input, can you use PLL IC 565 and a filter for around 1Khz for the same? As AnalogKid said, 2Khz is a bit high for human whistle.

Regards,
Manu

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8. ### ColinMember

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I did it all with a PIC chip.
Otherwise it takes a lot of parts

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I would imagine by the text that this is a "filter" project!!! Once upon a time there was analogue electronics...

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11. ### SbudaNew Member

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i was too close to the mic when i whistled, but i will try to redo measurements again with the lower frequency.... about the single pole filters and corner frequencies i think it's my first time hearing about those.

Last edited: Oct 16, 2017
12. ### audioguruWell-Known MemberMost Helpful Member

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The tone controls on your stereo are single pole filters. They reduce the high and low frequencies a little, they do not remove them. The simple "whistle" detector will also detect a dog barking or an airplane or a motorcycle.

13. ### audioguruWell-Known MemberMost Helpful Member

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2kHz is too high for a human to whistle? I am a human and I can easily whistle 2kHz or 1kHz or 500Hz and many more frequencies.

14. ### SbudaNew Member

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how to make it?

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