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Final Project Review
Team Vibraid
April 2014
VibraidMichael Balanov(Mike) EE
Spyridon Baltsavias(Spiros) EE
Reona Otsuka(Leo) EE
Andrew Woo(Andy) EE
Previous Block Diagram
44
4 4 4 4
switch signal
variable resistance
variable resistance
• 5 different modules
• Processing done in software, everything else in hardware
Current Block Diagram
• Processing block absorbs Filtering module
• Filtering done digitally!
Reason behind Digital Filtering
• Analog filters attenuated input signal
• Extra amplification was required
• Physical space limitation
• 3 filters per microphone = total of 12 filter circuits
• Additional space for extra amplification/active filter
• Digital advantages
• Ideal band cutoffs
• No attenuation
• Allows for easy combination of filters
Arduino Processing Changes• Optimized through low level coding to increase sampling rate
• From 2.5kHz to around 14kHz rate for each microphone
• Implemented an optimized FFT to determine frequencies received by the microphones
• If fundamental frequency is inside desired band, pass signal for comparison
• Block low-pass noise that was observed
• Due to limited analog inputs, the Motor strength knob has been changed to a Motor strength switch
Final Comparator Logic Design
• Decided to implement SPL (amplitude) comparison instead of Time Delay estimation
• Time Delay could not be improved enough to meet the required specs
• SPL comparison met specs after purchasing better directional microphones
FPR RequirementsSpecification Value Met?
Max Detection radius for 70dB to 120dB within frequency range
>3m (10ft) Yes
Frequency Detection Range 100Hz – 10kHz Yes, in most cases
Belt Circumference 75cm – 105cm (small – large) Yes
Belt Width <10cm Yes
Belt Thickness <5cm Yes
Product Weight <1kg Yes
Detection Directionality 4 Directions Yes
Vibration Response Time <0.5s Yes
Vibration Directionality Vibration to alert user in one quadrant
Yes
Vibration to Corresponding Detection
99% of time Yes
Tunable Sensitivity Block all till Pass all Yes
Tunable Frequency Detection 4 modes: full, low, mid, high Yes
Tunable Motor Strength No vibration to Max supply No (2 levels of intensity instead)
Battery Life >12h Yes
Demo Outline
• Frequency filtering demo
• Wearing the device – 4 way directionality
Frequency Filtering
• 3 switches: High, Mid, Low (-pass)
• Low band: 100Hz to ~300Hz
• Mid band: ~300Hz to 600Hz
• High band: ~600Hz to ~7000Hz
• Combination of bands possible
Q&A
Digital Filtering Disadvantages
• Sampling rate needs to be high enough (Nyquist rate)
• Adds to processing time