Group Members:Mike Oertli

Jonathan KarnuthJason Rancier

September 11, 2008

Project OverviewLinear acceleratorVoltage applied to railsProjectile shorts out rails creating EM fieldPneumatic kick-startProjectile accelerates forward

Basic DesignConducting rails mounted to non-conducting

surfaceCapacitor arrayPCB, logic, and UIConducting metallic projectile

ObjectivesSafety!!!Adjustable voltage from capacitor bankUser interface

Keypad and LCDSensor dataVelocity calculationsRemote/Hands off (Safety!)

Approach Split into 3 main areas

1. Railgun2. Control system3. User interface

Each person focus on one area

Communication and compatibility is key

Power SupplyBrute Force discharge

Basic supply, dumps a lot of current directly on rails

Simple to design, overkill on capacitanceInefficient, back EMF problems

Recharger SupplyComplex LC timing based on railsProne to failure with bad designRequires more capacitors (if polarized are used)Much more efficientFast recharging

Capacitors Capacitance: 610,000µFVoltage: 20VDC

30VDC surgeESR: 2.1mΩ maxType: ElectrolyticNumber used: ~20Cost: ~ $400

Capacitor ArrayMounted capacitors

Connected by switches controlled by logic based on input voltage from user

Logic will be based on test shotsIn enclosed case (Safety)

Other possibilities:Manual switchesSwitch mode power supply

Input inductor between array and railsRamps current to railsAvoid discharging capacitors too fast

Rail typesCylindrical

Easier to fabricateFewer piecesStronger using less material

RectangularEasier to mountBetter electrical properties, distributed current

Example of rail

Conducting rails

MaterialsRails: BrassProjectile: AluminumBase: Garolite & TeflonCapacitors: 20x 0.6F 20 v ElectrolyticMicrocontroller: MSP430 family - 16 bitPCBPower supplySensors (EM, voltage)Keypad and LCD

Brass RailsComposite: ~70% Copper, ~.07% Lead,

~.05% Iron, Remainder ZincElectrical Conductivity: 28% IACSElectrical Resistance: 6.2µΩ/cmFriction: Very low with Most metalsMelting Point: 910oCInner/Outer Diameter: 0.87”/1”Cost: $58.68 for 36”

ProjectileMetal: Aluminum

Composite: 2011Temper: T3Part #: 88615K411

Melting point: 540oC Electrical Conductivity: 45% IACSElectrical Resistivity: 3.8µΩ/cmDiameter: 7/8”Length: ~1”Cost: $17.41/foot

Pneumatic Kick-start Avoids spot welding projectileAdded kinetic energyEliminates static friction coefficientsCompressed Air/CO2 system

Activated by Microcontroller post safety checks

Chassis SpecsInner Support Outer Sheath

Composite Teflon PTFE Grade G-10/FR4

Crosswise Tensile Strength

3,900 PSI 35,000 PSI

Melting Point 335oC ~384oC Max Temp

Dielectric Strength 19.7MV/m 15.7MV/m

Inner/Outer Diameter

.875”/1” 1”/1.375”

Cost $9.21 per 12” $92.16 for 39”

Part # 8547K29 8668K49

Safety FeaturesVoltage sensors on rails, cap bank, & source

Kill power if out of expected rangeEM Field Sensor

Faraday cage if EM field great enoughPlexiglas casing

Keep user isolated from high voltages and short circuited rails

Block Diagram

MSP430xxxx

Power Supply

Keypad

LCD

RailsCapacitor Array

KillSwitch

LEDs

Inductor

MicrocontrollerMSP430xxxx family

Testing on MSP430F16916-bit for accurate calculation of sensor dataControl safety logic based on sensor values

Disconnect switches from caps to railsDisplay values on LCD

Software EngineeringInterface with Matlab

Import sensor dataStatistical analysisDisplay results to user as graphs and tablesMaintain records

PCB ElementsPower supplyMSP430 FamilyDebug/information LEDsLCD (3 or 4 rows)Keypad inputCommunication with sensors(A/D)

SensorMeasure voltage at high sample rateUsed for analysis and safety logicImplementation:

Voltage transducerSample @ 10 MHz +Response time < 50μs

User InterfaceBasic keypad

Input desired voltage to apply to rails3 or 4 line LCD on PCB

Output sensor data and statisticsBasic input user interface

If time:Keyboard inputComputer monitor with GUIMatlab sensor data analysis

ExpensesItem # Needed Cost per Total Cost

Rails 2x36” $58.68 $117.36

Garolite 2x42” $46.53 $120

Capacitors 20 $20 $400

Projectiles 1’ $17.41 $17.41

PCB 2 $30 $60.00

Controller 3 (donated) $0

Misc/Sensors $300

Estimated Total ~$1014.77

Division of LaborJonathan Mike Jason

Primary Responsibility

Rail fabrication &Safety

Microcontroller& Safety

Power systems &Safety

Schedule

“Real World” ApplicationControl System for other high voltage

applicationsAccelerator for fun, military, other scientific

researchCapacitor array for high current burst power

systemsSensor to Matlab interface

RealizationStay under budget by getting donationsEstablish primary goals/reasonable

functionalityOperate within these

Add incremental levels of difficulty based on time

Plan BRisk:

Projectile fuses to rails Discontinuities in the rails and base Arcing- heat/damage to rails

Unfamiliarity Sensing systems Matlab interface

Recovery Ask for help! Use heavier duty components RTFM Have extra rails and projectiles ready

Questions?