detailed design review and test plan project 7: drifters

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Detailed Design Review and Test PlanProject 7: Drifters

Lance Ellerbe - BS EEJamal Maduro - BS CpE

Peter Rivera - BS MEAnthony Sabido - BS ME

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Drifter Design Team

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Project OverviewDevelop a self-contained network of tracked surface drifters for near coastal application.

HousingElectronics

Power SystemGPS receiverRadio transceiverMicrocontroller

Any of these drifters within range of the base station will then be able to send all the information from all other drifters, thus providing a self-contained drifter network.

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Electrical Components Microcontroller:

TI (Texas Instruments) MSP430G2553 microcontrollerRadio Transceiver

XBee-Pro XSC RF module’s GPS module:

Maestro A2100 Battery

Lithium ionTemperature Sensor

Maxim DS18B20

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Microcontroller, Radio Transceiver, and GPS

Engineer: Jamal Maduro

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QUICK REVIEW

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Microcontroller

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XBee Modes of Operation

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XBee Data Verification Chain

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GPS Diagram

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Temperature SensorOverviewCompared to the thermistor, the DS18B20

has memory and thus the temperature can be held until a more convenient time when the data can be logged.

Digital temperature sensor that uses serial communication through the DQ pin.

1 temperature reading per GPS fixConverts Temperature to 12-Bit Digital Word

in 750ms (Max)

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UPDATED SYSTEM

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General Layout

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System Flow Chart

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Completed Tests1. UART Test (Completed)A loop back circuit was made by connecting the microcontroller’s transmission pin to the receiving pin and then the following test programs located in the appendix were ran:

• “UART_loop_9600baud.asm” – a continuous stream of data at a constant baud rate • “UART_echo_9600baud.asm” – real-time data input response at a constant baud rate

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Completed Tests2. SPI Test (Completed)A loop back circuit was made by connecting the microcontroller’s SOMI to the SIMO pin of another identical microcontroller (or loop back within one microcontroller), connecting and synchronizing, and their corresponding clock pins to one another. The output was viewed on a terminal emulator.

• “SPI_UART.asm” – data passed in through UART transferred to SPI and outputted out of UART

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Completed Tests3. Timer Test – System wakeup simulation (Completed)The watchdog timer is configured to alternate two LEDs every 10 seconds and output a character via UART and SPI. Various time intervals were tested including the actual time that the tracking system will be asleep and active.

• “Low_Power_Timer_Comm.asm” – data passed in through UART transferred to SPI and outputted out of UART transitioning out of low power mode.

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Completed Tests4. Sleep Mode Test (Completed)The microcontroller was connected to a digital multi-meter and the voltage level of all of its operation modes were recorded to ensure that the desired reduction in power consumption was achieved.

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Completed Tests5. XBee UART Communication (Completed)A circuit was made by connecting the microcontroller’s transmission pin to the receiving (Din) pin of the XBee and the output (Dout) from the XBee was connected to a RS-232 level shifter via a DB9 connection to a laptop computer and was observed on a terminal while running the test program located in the appendix:

• “UART_cmd_57600baud.asm” – send binary commands to the XBee radio module

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Completed Tests6. XBee Firmware Test (Complete)Connect the XBee module to the RS-232 level shifter via a DB9 connection to a laptop computer and verify that the default settings are correctly initialized such that the default interface is binary command mode as opposed to AT command mode. Configure the desired settings if the default is incorrect and retest to ensure that firmware has been correctly updated and will not be reset upon loss of power.

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Pending Tests1. GPS SPI Communication (Pending...)A circuit will be made by connecting the microcontrollers SOMI pin to the SIMO pin of the GPS module, connecting and synchronizing their corresponding clock pins, and observing the data collected by the microcontroller in its RAM and/or registers.

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Pending Tests2. Temperature Sensor GPIO Communication (Pending...)A circuit will be made by connecting a GPIO on the microcontroller to the DQ pin of the digital temperature, different heat sources will be applied to the sensor and the output will be compared against a thermometer to ensure that the sensor is functioning correctly. The GPIO will be switched from input and output as needed.

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Pending Tests3. GPS Firmware Test (Pending...)Connect the GPS module to the RS-232 level shifter via a DB9 connection to a laptop computer and verify that the default settings are correctly initialized such that the only output is the NMEA RMC string. Configure the desired settings if the default is incorrect and retest to ensure that firmware has been correctly updated and will not be reset upon loss of power.

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Pending Tests4. Data Logging File System Test (Pending...)Connect the data logger (with the desired memory card inside) to the RS-232 level shifter via a DB9 connection to a laptop computer and verify that the file system is correctly configured. Test all immediately relevant operations such as reading, writing, and erasing data.

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Pending Tests5. Temperature Sensor Serial Comm Test (Pending...)The temperature sensor will be tested in conjunction with the microcontroller. The timing limits of communication will be tested using the timer in the microcontroller to ensure that the suggested timing protocol in the datasheet will support correct functionality.

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Antennas and Power Systems

Engineer: Lance Ellerbe

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Antennas

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Radio Transceiver AntennaThe antenna has a operational frequency between

868MHz-928MHz. This frequency range will allow the for the drifter to

operate by relaying its position to nearby drifters via radio transmission on the 915MHz ISM (Industry, Scientific, Medical) band.

The antenna has a gain of 3.1 dB, doubling the signal strength (an output-to-input power ratio of 2:1) which translates into a gain of 3 dB which is the half power point.

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Radio Transceiver AntennaInterfacing Radio Transceiver antennaThe radio transceiver antenna will be the

implemented into the drifter system through the Xbee transceiver using a U.FL connector adaptor. This connector cable interfaces U.FL RF connectors to RP-SMA antennas.

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GPS AntennaSL1204 GeoHelix.

Active Antenna

Gain of +18 dB

Beam width of 135o .

Operational voltage: 1.8-3.6V

Draws 3.4 mA max

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GPS AntennaInterfacing GPS antennaThe Maestro A2100 also supports active antennas

directly, by offering an antenna voltage feed pin (VANT – pin 15)

GPS module provides a maximum current draw of 50mA. This active antenna should have a gain ≥ 15dB but the

total gain should not exceed 30dB. 50 Ω PCB strip line is required

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Power Systems

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Power SystemsOverviewLow Power ConsumptionEach must be able to operate on 3.3V maximum.The drifter network will be designed to use the least

amount of power when transmitting data.The power supply will be selected in order to supply the

adequate amount of amp-hours in order to provide enough current for each electrical component to be operational throughout its 15 day deployment.

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Power SystemsCurrent Component Selection : Xbee

Operation Voltage: 3.0 -3.6VDC Current Draw:

Transmitting current: 256mA Receiving Current: 50 mA

Maestro A2100-A/B Operation Voltage: 3.0V - 3.3VDC Current Draw:

Peak Acquisition Current 45mA Antenna current: 3.4 mA

Microcontroller Operation Voltage: 1.8V - 3.6V Active mode: 230uA Standby Mode: 0.5uA

Temperature Sensor Current Draw: 1.5mA

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Power SystemsVoltage Regulator

MAX882/MAX883/MAX884 line regulator

The regulator input supply voltage can range from 2.7V to 11.5V

Low Dropout Voltage: 220mV

Fixed Output voltages: 3.3V and 5V

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Power SystemsPCB protectionLithium Ion batteries must connect to a protection circuit

module to protect Li-Ion Battery from overcharge, over discharge and to prevent accidental battery explosion due to its extra high energy density.

Battery

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Power SystemsCurrent Component Selection PROGRESS:Worst Case Scenario: 1 sec for each transmission/reception

401.23 mA for 2.77 hours of ACTIVE operation

sleep mode considered negligible (uA range).

401.23 mA × 2.77 hours = 1111.407 mAh

Battery needed would be something with 3.3 V and a capacity greater than 1111.407 mAh to adequately provide enough current to stay operational for a 15 day deployment.

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Power SystemsBatteryUltrafire 18650 Protected Rechargeable

Lithium Ion Battery

Nominal Voltage: 3.7V

Capacity: 3000mAh

The PCB protection that is needed for Lithium Ion batteries already integrated in the battery.

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Power SystemsBattery Configuration

•Parallel configuration would be ideal to increase the amount of Amp-Hours to supply the adequate amount of current to Microcontroller, GPS module, Radio Transceiver and Temperature Sensor for a 15 day period.

Using 3000 mAhBatteries

V 2

3.7 VDCV 3

3.7 VDC

Voltage = 3.7 V

Capacity =6000mAh

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Power SystemsPower Systems Diagram

LBOV 1

3 . 7 V d c

GNDPCBProtector IN

+-

V 2

3 . 7 V d c

LBI

OFF(STBY)

OUT

Max882/884GND

SET

Delivers 3.3V to the power supply pin of each component in the system

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Power SystemsComponent TestingThe testing of this task will include a number of power

consumption tests. First, each electrical component will be attached separately to a multimeter or oscilloscope to validate that the component is operating within its electrical specifications.

Second, based on the results in the previous step the results can be then used to tweak network parameters such as transmission time or microprocessor algorithms in an attempt to lower power consumption and increase theoretical operation time.

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Power SystemsVoltage Regulator Test The testing of this component in the power systems will test the different operation

of the MAX884 linear regulator.

Using a multimeter we will input different values of input voltages(2.7V to 11.5V) and measure the current and voltage on the output pin. The results from this test will show how the effects of different voltages and currents on the input pin will change the output current on the output pin on the voltage regulator.

Test the different capabilities of the voltage regulator such as Shutdown Mode or Standby Mode. Based on this test we will see which Mode will be best to achieve the least amount of power consumption, but also allows the regulator to activate when needed.

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Power SystemsBattery test

The testing of the battery includes testing the battery under a load similar to the drifter system to see how long the battery can last.

In this test we will connect the battery to a simulated load that draws approximately 400mA of current and test the battery over a certain amount of time. We would record the batteries beginning voltage and current, then record the voltage and current after the battery has been drained for a certain amount of time. This test would ensure that our drifter system will adequately be powered throughout a 15 day deployment.

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Hull DesignEngineers: Anthony Sabido and Peter Rivera

PROPOSED DESIGNOverview

Major Features:•Symmetric•Semi-Circular Profile•Fiberglass Hull

•Off-the-Shelf Deck Plate•Low Cost•Easy Fabrication

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31.Top2.Bowl3.Screw-

in Deck

Plate

FiberglassLow Density:

Cloth: 2.6 g/cm3

Resin: 1.3 g/cm3

Low Cost205-B Slow hardener (0.86qt.): $37.20105-B Epoxy Resin (1 gal): $78.29

Sealing the Hull6” diameter

deck-plateScrew-in designMade of

Durable ABS plastic

O-ring for water tight seal

Low cost - $7.89

Proposed designUpdated Hull

Mass CalculationsComponent Mass (Legacy)  

Antenna 9.1 gGPS Antenna 9.1 gGPS Module 4.5 gRadio Transceiver 4.5 gBatteries (2) 45.4 gBoard w/Processor 40.0 gHull 2400 g

Total 2513.1 g

Component Mass (New/Proposed)  

Antenna 26.87 gGPS Antenna 8.01 gGPS Module 1.33 gRadio Transceiver 3.87 gBatteries (2) 45.4 gMicroprocessor 1.22 gDeck Plate 309.7 gHull 1962.7 gSD Breakout Board 5.51 gSD Card ~5 gTemp Sensor <1 gPrinted Circuit Board ~40 g

Total 2410.3 g

Initial Dimensions- Drifter

Updated Dimensions- Drifter

Updated Dimensions- Drifter

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Major Changes - Dimensions

Radius of the hull’s contour decreased from 15” to 10.875”

Major diameter decreased from 47.24cm to 38.68cm

Overall hull height decreased from 9.40cm to 7.55cm

# - Latest Dimensions

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Design Validation- Component Fitment

Each major component has been solid modeled to ensure fitment into the hull

Masses added to double-check the center of mass

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Final Updates

2 Piece Hull Design changed to 3 piece assembly

Deck plate purchased is smaller and lighter

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Exploded View

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Final Updates

2 Piece Hull Design changed to 3 piece assembly

Deck plate purchased is smaller and lighter

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Rough PCB Footprint

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Final Updates

2 Piece Hull Design changed to 3 piece assembly

Deck plate purchased is smaller and lighter

Temperature sensor placement finalized

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Temperature Sensor

Testing DetailsPerformance Analysis

Testing in DetailPreliminary Floatation

Check water level. Our goal is to have the drifter sit low enough in the water to avoid wind drag but not too low that it loses stability.

By adjusting the diameter and bowl depth, we can change the volume and draft level.

We can perform this test in any body of water

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TestsPreliminary Water tightness / Floatation TestsPreliminary Stability TestsOn-Site Stability TestsFinal Water tightness tests

Testing in DetailPreliminary Water tightness

Even a slight water leak in an electrical system can be catastrophic

While testing floatation, we will also examine the drifter’s hull for leaks. After floating the drifter for several minutes, we can examine the inside to check if water entered the compartment.

At Sea TestsAfter the initial tests to confirm stability, floatation, and

water tightness, we will take the hulls to the test area (Ochlocknee Bay) to examine their behavior with a payload of equivalent weight of the electrical components.

Testing in DetailFinal Water tightness

Our final test will involve placing an empty drifter hull at the bottom of a pool of water approximately 5m deep.

There is a chance that the drifter could, under some circumstances, be completely submerged at depths of around one meter.

This test would allow for a safety factor.

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Testing of All HullsThough the on-site test at Ochlocknee Bay

will be performed on only a select few designs, each hull constructed will undergo the series of tests listed before.

Assuming that because one individual hull completed the tests does not guarantee that some small imperfections in a later copy will allow all the drifters to perform on par.

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Base StationThe base station will be a mostly stationary

system.The initial use by the sponsor will involve

holding the base station in hand or on a boat.Later use will involve leaving the base station

unattended. To save money, the base station will not

require a GPS receiver (or antenna) and will not require a regular drifter hull.

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Base StationThe container of the base will be placed in an otterbox.

Otterboxes are waterproof boxes (up to 100ft) that also float.

This design will allow the sponsor to leave the base station out in the elements for extended periods.Or place the station on the roof of a building and connect a

high-gain tower antenna for better reception.

This box is an Otterbox 3000. It’s dimensions would allow the use of the same PCB placed in the regular drifters.

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Project Timeline & Budget

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Project Overview - TimelineWeek # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Week Dates 1/1 - 1/7

1/8 - 1/14

1/15 -

1/21

1/22 -

1/28 1/29 - 2/4

2/5 - 2/11

2/12 -

2/18

2/19 -

2/252/26 - 3/3

3/4 - 3/10

3/11 -

3/17

3/18 -

3/24

3/25 -

3/314/1 - 4/7

4/8 - 4/14

4/15 - 4/21

Finish Code

Test Xbee Range Milestone 1

- M1 Report

- M1 Presentation

Finalize Hull Design

- Construct Prelim. Hullls

- Test Stability

- Test Watertightness

- Secondary Hull Testing

Test GPS - Mount GPS Chip Order PCB - Design PCB

Test Networking Capabilities

Purchase Batteries - Determine Quantity Fabricate Base Station - Select Otter Box Test Power Systems

Develop Instruction Manual

Milestone 2

Milestone 3

- M3 Report

- M3 Presentation

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Project Percentage Complete

59.5%

40.5% Remaining

Complete

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BudgetExpenses Quantity Unit Price Total ShippingMicrocontroller 6 2.80$ 16.80$ 8.90$ USB to RS232 Adapter 5 11.95$ 59.75$ 18.78$ RS232 Shifter 5 13.95$ 69.75$ 13.84$ Development Board 1 4.35$ 4.35$ 9.34$ Deck Plate 4 7.89$ 31.56$ xxxxFiller Compound 1 pint 15.50$ $15.50 xxxxFiberglass Resin 1 gallon 78.29$ 78.29$ xxxxFiberglass Hardener 0.86 qt 37.20$ 37.20$ xxxxMem. Card Breakout Board 5 9.95$ 49.75$ 12.77$ GPS Antenna 5 22.95$ 114.75$ xxxxTemperature Sensor 5 4.25$ 21.25$ xxxxAntenna Adapter 5 4.95$ 24.75$ xxxxRadio Transciever 5 39.00$ 195.00$ 15.00$ GPS Module 5 19.44$ 97.20$ xxxxRadio Antennas 5 7.95$ 39.75$ 12.00$ Fiberglass 15 sq ft $ 4.74 / sq ft 71.10$ xxxxBatteries 10 10.50$ 105.00$ 10.00$ Voltage Regulator 5 3.50$ 17.50$ 9.00$ Printed Circuit Board 5 13.75$ 110.00$ 18.00$ PCB Protection Module 5 3.90$ 19.50$ 7.00$

Totalw/Shipping

Column Totals: 1,178.75$ 134.63$ 1,313.38$

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Questions

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ReferencesTechnical Report: “Surface Circulation Study of Waters Near Ochlockonee Bay, Florida”- Peter Lazarevich and Dr. Kevin Speer

Project Description : “Tracking the coastal waters: a wireless network of shallow water drifters”- FAMU-FSU College of Engineering

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Appendix