1. Soil Testing Data Logger Mid-Semester Presentation October 7, 2010

2. Team Members Cody Griffin Op Amp Circuitry PCB Design Hardware Testing Normal Mode Design Electrical Engineering Daniel Herrington Software Design Lead VDIP Communication Software Testing Website Design Electrical Engineering Ashley Stockbridge RTCC Software Design Test Mode Design Normal Mode Design Software Testing Electrical Engineering Matt Weissinger PCB Design Op Amp Circuitry Hardware Testing Component Research Electrical Engineering

3. Outline Background Problem Solution System Overview Constraints – Technical – Practical Trade Offs Timeline Progress

4. 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

5. 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

6. 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

7. System Overview Soil Potential Input Circuit StorageMicrocontroller Power Supply Temperature Input

8. Constraints Technical Constraints Practical Constraints

9. Technical Constraints ConstraintDescription InputsThe 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. Data StorageThe device must store soil redox potential and temperature data on a removable USB storage device. Sample RateThe device must store sample data every 20 minutes.

10. Practical Constraints TypeConstraintDescription ManufacturabilitySizeThe size of the circuit board must be no larger than 3.1” x 3.9”. EnvironmentalOperating ConditionsThe device must be able to operate in extreme weather conditions.

11. Manufacturability No larger than 3.1” x 3.9” Easily accessible for routine maintenance Organized for easy assembly

12. Environmental Cleveland, MS

13. Design Issues High Impedance Soil Probes Possible Negative Input Voltages Accuracy Constraint

14. High Impedance Soil Probes +_+_ Soil Probe V+ V- +/- 600 mV

15. High Impedance Op Amp Input Bias Current Power Supply Input Offset Voltage PriceComponent Chosen LMP 223420 fA1.6 V150 uV$6.38 NJU 70041 pA1.0 V10 mV$2.01

16. Voltage Inverter Output RangeAccuracyPriceComponent Chosen TL 76601.5 – 10 V99 %$1.40 MAX 7641.0 – 16 V99.9 %$9.96

17. Negative Input Voltages +_+_ Soil Probe V+ V- +/- 600 mV

18. Negative Input Voltages +_+_ +_+_ Soil Probe 1.250 V Reference To PIC ADC V+ V- R3 R4 R1 R2

19. Voltage Summing Op Amp Input Offset Voltage Power Supply Output Type Number of Circuits Component Chosen LT 1496200 uV2.2 VRail To Rail 4 OP 290125 uV1.6 VN/A2

20. Voltage Reference ToleranceCostComponent Chosen LM 285±0.97 %$1.26 LT 1634±0.05 %$10.38

21. Timeline AugustSeptemberOctoberNovember Research Hardware Design Software Design Prototype Testing Final Product

22. Progress Hardware Design – 100% Complete – High Impedance Voltage Follower Circuit – Complete – High Accuracy Voltage Summer Circuit – Complete Software Design – 75% Complete – RTCC – Complete – Test Menu – Complete – VDIP1 Communications – Complete – Normal Operation Mode – 50% Complete

23. Hardware Design

24. Hardware Testing 1.469

25. Software Design

26. References [1] “Season Weather Averages for Mid Delta Regional,” Weather Underground. 2010. http://www.wunderground.com/NORMS/DisplayNORMS.asp?AirportCode=KGLH&SafeCityName=Cle veland&StateCode=MS&Units=none&IATA=GLH http://www.wunderground.com/NORMS/DisplayNORMS.asp?AirportCode=KGLH&SafeCityName=Cle veland&StateCode=MS&Units=none&IATA=GLH [2] “LMP2234 Datasheet,” National Semiconductor. 2008. http://www.national.com/pf/LM/LMP2234.html#Overview http://www.national.com/pf/LM/LMP2234.html#Overview [3] “NJU7004 Datasheet,” New Japan Radio. 2005. http://semicon.njr.co.jp/njr/hp/productDetail.do?_isTopPage=false&_productId=143&_moveKbn=PR ODUCT_DETAIL_MOVE_SPEC http://semicon.njr.co.jp/njr/hp/productDetail.do?_isTopPage=false&_productId=143&_moveKbn=PR ODUCT_DETAIL_MOVE_SPEC [4] “TL7660 Datasheet,” Texas Instruments. 2006. http://focus.ti.com/docs/prod/folders/print/tl7660.htmlhttp://focus.ti.com/docs/prod/folders/print/tl7660.html [5] “MAX764 Datasheet,” MAXIM. 1994. http://www.maxim-ic.com/datasheet/index.mvp/id/http://www.maxim-ic.com/datasheet/index.mvp/id/ [6] “LT1496 Datasheet,” Linear Technology. 1997. http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1009,C1021,P1568 http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1009,C1021,P1568 [7] “OP290 Datasheet,” Analog Devices. 2009. http://www.analog.com/en/amplifiers-and- comparators/operational-amplifiers-op-amps/op290/products/product.htmlhttp://www.analog.com/en/amplifiers-and- comparators/operational-amplifiers-op-amps/op290/products/product.html [8] “LM385 Datasheet,” National Semiconductor. 2008. http://www.national.com/mpf/LM/LM385- ADJ.html#Overviewhttp://www.national.com/mpf/LM/LM385- ADJ.html#Overview [9] “LT1634 Datasheet,” Linear Technology. 1998. http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1002,C1804,P1611 http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1002,C1804,P1611

27. Questions?