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

2. Outline Problem: Rodents infesting crops Rodent Alert with Sensor design – Microphone sensor Testing Future work Other applications References 2/16

3. Rodents infesting crops by 1974, rodents responsible for annual loss of 33 million tones of stored cereals and rice Rodents may carry and transfer diseases 3/16

4. Rodents infesting crops Recent Rising Example: Snail farming – Mice are a threat to snail farming 4/16

5. Rodents infesting crops Fields: Detect rodent presence How? – Microphone sensor 5/16

6. 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 6/16

7. Microphone sensor Components: – Microphone – Low Voltage Audio Power Amplifier(LM386) – Microcontroller unit(C8051F320) 7/16

8. 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? 8/16

9. 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) 9/16

10. 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 10/16

11. 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) 11/16

12. Microphone sensor(circuit) 12/16

13. Testing 13/16

14. 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) 14/16

15. Other applications Besides rodent detection: – Sensor could detect certain insects Higher frequency sounds Change sampling frequency 15/16

16. References http://www.boltonmousecontrol.co.uk/ http://digitalcommons.unl.edu/cgi/viewconte nt.cgi?article=1046&context=gpwdcwp http://digitalcommons.unl.edu/cgi/viewconte nt.cgi?article=1046&context=gpwdcwp http://www.snailfarming.gr http://en.wikipedia.org/wiki/Mouse http://www.ratbehavior.org/rats.html 16/16