TEL412 Exam Project Design of sensor for detecting rodents Kονταδάκης-Ντίλης ΗΜΜΥ...

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TEL412 Exam Project Design of sensor for detecting rodents Kονταδάκης-Ντίλης ΗΜΜΥ Πολυτεχνείου Κρήτης, Ιανουάριος 2011 1/16
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Transcript of TEL412 Exam Project Design of sensor for detecting rodents Kονταδάκης-Ντίλης ΗΜΜΥ...

TEL412 Exam ProjectDesign of sensor for detecting

rodents

Kονταδάκης-ΝτίληςΗΜΜΥ Πολυτεχνείου Κρήτης, Ιανουάριος 2011

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Outline

• Problem: Rodents infesting crops• Rodent Alert with Sensor design– Microphone sensor

• Testing• Future work• Other applications• References

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Rodents infesting crops

• by 1974, rodents responsible for annualloss of 33 million tonesof stored cereals and rice

• Rodents may carry andtransfer diseases

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Rodents infesting crops

• Recent Rising Example: Snail farming– Mice are a threat to snail farming

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Rodents infesting crops

• Fields: Detectrodent presence• How?– Microphone sensor

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Microphone sensor

• Rodents make high frequencies sounds– Example: Rat squeak at 2.5 - 5 kHz– Easily distinguishable from human voice(<1 kHz)– and common environmental noises(<1.5 kHz)

• Result: cut low frequencies(<2 kHz)• Sampling frequency at least 10 kHz

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Microphone sensor• Components:– Microphone– Low Voltage Audio Power Amplifier(LM386)– Microcontroller unit(C8051F320)

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Microphone sensor

• Processing signal in MCU• Find basic frequency of sound• FFT not suitable– Main problem: needs memory– C8051F320 has 256 bytes of data memory most of

which are reserved

• We need real time processing. How?

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Microphone sensor(Zero Crossing)

• Zero Crossing Implementation– ADC sampling frequency: fs = 10 kHz

– Take window of 30 ms => (0.03*10000) samples =300 samples

– Separate data to training and testing • 100 samples training(10 ms)• 200 samples testing(20 ms)

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Microphone sensor(Zero Crossing)• Training(100 samples)– Find Threshold(mean on samples)

• Testing(200 samples)– Check how many times signal crosses threshold– Then f0=(times*fs)/(2*samples) Hz

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Microphone sensor(Zero Crossing)

• Summary– Faster than fft(O(n) instead of O(nlogn))

– Finds only basic frequency of sound

– Not good for very low frequencies(<100 Hz)

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Microphone sensor(circuit)

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Testing

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Future work

• Problem with circuit– Voltage drops slowly after sound detection– Smaller accuracy on measurements

» Example: when fs = 10 kHz(demo) , cannot detect sound frequencies around 1.5 kHz

• Send detection result to base station(e.g. farmer)

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Other applications

• Besides rodent detection:– Sensor could detect certain insects• Higher frequency sounds• Change sampling frequency

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References

• http://www.boltonmousecontrol.co.uk/• http://digitalcommons.unl.edu/cgi/

viewcontent.cgi?article=1046&context=gpwdcwp

• http://www.snailfarming.gr• http://en.wikipedia.org/wiki/Mouse• http://www.ratbehavior.org/rats.html

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