Soil Testing Data LoggerFinal Presentation

April 21, 2011

Team Members

Cody Griffin

Op Amp CircuitryVDIP CommunicationHardware TestingNormal Mode Design

Electrical Engineering

Daniel Herrington

Software Design LeadVDIP CommunicationSoftware TestingWebsite Design

Electrical Engineering

Ashley Stockbridge

RTCC Software DesignSetup Mode DesignNormal Mode DesignSoftware Testing

Electrical Engineering

Matt Weissinger

PCB DesignOp Amp CircuitryHardware TestingComponent Research

Electrical Engineering

Outline

• Background• Problem• Solution• Constraints

– Technical– Practical

• Refinements• Packaging• Production• System Testing

Background: Soil Redox Potential

• Electrical property of soil that correlates to the specific chemicals present in the ground

• Research topic of Dr. Kroger with the Forest and Wildlife Research Center at MSU

Problem: Chemical Runoff

• Caused by fertilizers and pesticides used on farmlands

• Can be controlled using a detailed historical set of soil redox data

• No efficient method for collecting soil redox measurements

Problem: Chemical Runoff

[1]

Solution: Soil Testing Data Logger

• Reduces the time associated with taking soil redox potential measurements in the field

• Periodically takes soil redox potential and associated temperature measurements

• Stores all measurements in a removable USB storage device

Technical Constraints

Constraint Description

Inputs The device must support four soil probe inputs and five temperature inputs.

Soil Redox Potential Input Range

The device must be able to measure potentials that range from -600mV to +600mV with an accuracy of ±10mV.

Temperature Indicator Input Range

The device must be able to measure temperatures that range from -40°C to 125°C with an accuracy of ±1°C.

Data Storage The device must store soil redox potential and temperature data on a removable USB storage device.

Sample Rate The device must store sample data every 20 minutes.

Practical Constraints

Type Constraint Description

Manufacturability Size The size of the circuit board must be no larger than 3.1” x 3.9”.

Environmental Operating Conditions The device must be able to operate in extreme weather conditions.

Manufacturability

• No larger than 3.1” x 3.9”• Easily accessible for routine maintenance• Organized for easy assembly

Environmental

Cleveland, MS

[2]

Refinements

• PCB– Added third RJ45 connection– Added programming header– Minor silkscreen changes

• Software– Delayed start-up– Time-stamped filename– Refined setup menu

PCB Refinements

• Allows for grouping of soil/temp probe pairs• Lowers difficulty of manufacturing soil/temp probes

Software Refinements

• Delayed start-up– Useful to synchronize multiple data loggers– Easy initialization in setup menu

• Time-stamped filename– Filename is start date of sample period– Creates multiple files if more than one sample is

created in the same day

Packaging

• PCB is final packaging for data logger

• Soil / Temp probes are waterproofed using:– RJ45 cables– Heat shrink– Water tight sealant

Temperature Testing Data

Soil Redox Probe Testing Data

Production

Parts $61

PCB $24

Assembly $104

Total $189

[4]

[5]

[3]

References

[1] “The Gulf of Mexico Dead Zone,” Microbial Life: Educational Resources. 2011.http://serc.carleton.edu/microbelife/topics/deadzone/

[2] “Season Weather Averages for Mid Delta Regional,” Weather Underground. 2010. http://www.wunderground.com/NORMS/DisplayNORMS.asp?AirportCode=KGLH&SafeCityName=Cleveland&StateCode=MS&Units=none&IATA=GLH

[3] “Digikey,” Digikey. 2011http://digikey.com

[4] “PCBEX – Product Prices,” PCBEX. 2011.http://pcbex.com/Product/#2

[5] “Online Quote,” 2011.http://aapcb.com/online_quote.asp

Questions?Questions?