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