Dec1211

DISSOLVED OXYGEN MONITOR

TEAM MEMBERS: ANDREW BEOUGHER

ANTHONY SWOPE

HAO WANG

I -CHUN CHAO

BING BAI

COLIN HICKS

Senior Design Dec1211

Dec1211DISSOLVED OXYGEN MONITOR• Measures the concentration of dissolved oxygen (DO).

• Applications • Waste water treatment• Marine ecologies • Fermentation

Dec1211DESIGNOBJECTIVES

Re-engineer current design by removing or changing existing components.

• Lowering power consumption • Adjusting system timing of the sensor

Dec1211DESIGNREQUIREMENTS

Functional

• Microcontroller shall determine the dissolved oxygen level over 1 second

• Local and remote control operation• Long battery life during discontinuous operation

• 5 samples every 5 minutes• Operating duration of at least 30 days

Dec1211DESIGNREQUIREMENTS

Non-functional

• Water resistant monitor unit enclosure• Water proof sensor probe• Local multi-character LCD• Handheld / Portable

Dec1211SYSTEMCURRENT DESIGN

Batteries4 in Series

3.3V DC-DCConverter

5V DC-DCConverter

± 9V DC-DCConverter

5V DC-DCConverter

-5V DC-DCConverter

16.5V DC-DCConverter

LCD Module

DissolvedOxygen Sensor

Microcontroller

Wireless Communications

Module

Dec1211SYSTEMPROPOSED DESIGN #1

Dual Supply System

3.3V DC-DC Converter

Batteries4 in series

2 in series // 2 in Series4 in parallel

5V DC-DC Converter

LCD Module

DissolvedOxygen Sensor

With LED Driver

Microcontroller

Wireless Communications

Module

Dec1211SYSTEMPROPOSED DESIGN #2

Single Supply System

3.3V DC-DC Converter

Batteries4 in series

2 in series // 2 in Series4 in parallel

LCD Module

DissolvedOxygen Sensor

With LED Driver

Microcontroller

Wireless Communications

Module

Dec1211HARDWAREPROPOSED COMPONENTS

• Microcontroller

• ATXMega128

• LED Current Driver

• MAXIM - MAX3699• TI - TPS61042• Linear Devices - LT1932

• DC-DC Converters

• ADP - ADP150/151• TI - TPS61006• MAXIM - MAX1763

Dec1211HARDWARELED CURRENT DRIVERS

Why drive with current and not voltage?

0 ed

t

v

vI I

Id

Vdvt

Dec1211HARDWAREBATTERY CONFIGURATIONS

3 potential configurations

Dec1211SOFTWARECURRENT SENSOR TIMING

Sensor Timing Diagram

Pulse LED’s: 200 µsMeasure Emission Decay: 125 µs

Background Settling: 1500 µsMeasure Background Levels: 1250 µs

Waveform magnitudes are not to scale

20001800

LED’s

SensorMaterial

ADC

Time (µs)320030004002000

ADC Data Measurement

Do Not Care

Dec1211SOFTWAREPROPOSED SENSOR TIMING

Sensor Timing Diagram

Pulse LED’s: 200 µsMeasure Emission Decay: 125 µs

Background Settling: 375 µsMeasure Background Levels: 200 µs

Idle Time: 100µs

ADC Data Measurement

Do Not Care

Waveform magnitudes are not to scale

LED’s

SensorMaterial

ADC

Time (µs)4002000 600 800 1000

Dec1211TESTINGCOMPONENTS

• Power System:

• Power efficiency• Current output

• LED driver:

• Startup times• PWM output• Actual vs. computed current output

• Microcontroller:

• Power consumption of different modes

Dec1211TESTINGSYSTEM

Full System Test:

• Long term battery duration

Battery Duration Testing

I

it

t

I

tin

Accelerated Operation

Normal Operation tnc

Dec1211TESTINGSYSTEM

tc

t

nc

n

nc

op

i

N Number of short term test cycles

i Average short term test operation current

N Number of normal cycles

Average normal operation current

t Time duration of a normal cycle

t Estimated normal operation time

ttc t nc n tc nc op nc nc

n

iN i N i N N t N t

i

Dec1211PROJECTCURRENT STATUS

• Evaluate system operation

• Update customer requirements

• Perform component testing

• Create preliminary circuit board revisions

Dec1211PROJECTFUTURE PLANS

• Finalize new circuit board revisions

• Assemble new circuit board

• Perform long term battery duration tests

• Perform application and calibration testing

• Test programming modifications

• Re-integrate wireless communications

Dec1211

Questions?