A Mobile Sensor Platform for Indoor Location-Aware Navigation

By Ryan Patterson, L3D URA

Existing Technology

• Bluesoft, Inc. Wi-Fi Tags

• Mobile Phone Triangulation

• GPS (Global Positioning Satellites)

Method of Operation

Propagation Speed of Sound:

m/s

320 m/s 1049.6 feet/sec

)15.273(4441.402 Tc

Propagation Speed of RF:

c 2.998•108 m/s

983,571,058 feet/sec

Transmitter Development

3V Power Supply

(‘AA’ Batteries)

Ultrasound Transducers

(Transmitters)

Power Controlle

r

40 KHz High Precision Oscillator

12V, High Power Charge

Pump for Transmission

Transmission Control

Transmitter Development

Orange Trace shows Output to TransducersBlue Trace

shows Oscillator Digital Output

Receiver Development

3V Power Supply

(‘AA’ Batteries)

Third & Fourth Stage Amplification (Variable Gain, up

to 50)

5V Charge Pump for Power Supply

Analog DC

Voltage Converter

Low-Pass Filter (Gain 2), After Second

Stage

Signal Threshold Detection

First & Second Stage Amplification

(Gain 25)

Ultrasound Transducer (Receiver)

Receiver DevelopmentTransducer

Input1st & 2nd Stage

Amp (x25)Low-Pass Filter (x2)

3rd & 4th Stage Amp (x50)

Threshold Detector/Trigger

Amplitude Detection

Transducer Input (~3mV p-p); Transmitter within 5 feet

Attempt of High-Pass Filter

Orange is input; Blue is output

Receiver DevelopmentTransducer

Input1st & 2nd Stage

Amp (x25)Low-Pass Filter (x2)

3rd & 4th Stage Amp (x50)

Threshold Detector/Trigger

Amplitude Detection

Low-Pass Filter, no signal present (only noise); Orange

is input, Blue is output

Low-Pass Filter, weak signal present; Orange is

input, Blue is output

Receiver DevelopmentTransducer

Input1st & 2nd Stage

Amp (x25)Low-Pass Filter (x2)

3rd & 4th Stage Amp (x50)

Threshold Detector/Trigger

Amplitude Detection

Low-Pass Filter, weak signal present; Orange is

input, Blue is output

Output to microcontroller upon detection of signal

Receiver DevelopmentTransducer

Input1st & 2nd Stage

Amp (x25)Low-Pass Filter (x2)

3rd & 4th Stage Amp (x50)

Threshold Detector/Trigger

Amplitude Detection

4th Stage output; No signal (only noise); Full gain (x1250), Magenta is output, Green is trigger Threshold

4th Stage output; No signal (only noise); Attenuated gain (x800), Magenta is output, Green is trigger Threshold

Range TestingDistance (Feet) Receiver Signal Amplitude (V)

10 2.48 (Saturated)

20 2.48 (Saturated)

30 2.1

40 1.5

50 0.8

60 0.2

70 0.1

80 0.04

Amplitude as a function of Distance

0

0.5

1

1.5

2

2.5

3

10 20 30 40 50 60 70 80

Distange (Feet)

Am

pli

tud

e (

V)

Transmitter in windowsill

Power Consumption

Transmitter Power Consumption:

In Low Power Mode: 0 mA

In Standby Mode: 15 mA

While Transmitting:104 mAReceiver Power Consumption:

In Low Power Mode: ~0.001 mA

In Standby Mode: 37 mA

During Incoming Signal: 47 mAPower of Typical ‘AA’ Battery:

1850 mAH