Group Members:
Mike Oertli
Jonathan Karnuth
Jason Rancier
September 11, 2008
Project Overview
 Linear accelerator
 Voltage applied to rails
 Projectile shorts out rails creating EM field
 Pneumatic kick-start
 Projectile accelerates forward
Basic Design
 Conducting rails mounted to non-conducting surface
 Capacitor array
 PCB, logic, and UI
 Conducting metallic projectile
Objectives
 Safety!!!
 Adjustable voltage from capacitor bank
 User interface
 Keypad and LCD
 Sensor data
 Velocity calculations
 Remote/Hands off (Safety!)
Approach

Split into 3 main areas
1.
2.
3.
Railgun
Control system
User interface

Each person focus on one area

Communication and compatibility is key
Power Supply
 Brute Force discharge
 Basic supply, dumps a lot of current directly on rails
 Simple to design, overkill on capacitance
 Inefficient, back EMF problems
 Recharger Supply
 Complex LC timing based on rails
 Prone to failure with bad design
 Requires more capacitors (if polarized are used)
 Much more efficient
 Fast recharging
Capacitors
 Capacitance: 610,000µF
 Voltage: 20VDC
 30VDC surge
 ESR: 2.1mΩ max
 Type: Electrolytic
 Number used: ~20
 Cost: ~ $400
Capacitor Array
 Mounted capacitors
 Connected by switches controlled by logic based on
input voltage from user
 Logic will be based on test shots
 In enclosed case (Safety)
 Other possibilities:
 Manual switches
 Switch mode power supply
 Input inductor between array and rails
 Ramps current to rails
 Avoid discharging capacitors too fast
Rail types
 Cylindrical
 Easier to fabricate
 Fewer pieces
 Stronger using less material
 Rectangular
 Easier to mount
 Better electrical properties, distributed current
Example of rail
Conducting rails
Materials
 Rails: Brass
 Projectile: Aluminum
 Base: Garolite & Teflon
 Capacitors: 20x 0.6F 20 v Electrolytic
 Microcontroller: MSP430 family - 16 bit
 PCB
 Power supply
 Sensors (EM, voltage)
 Keypad and LCD
Brass Rails
 Composite: ~70% Copper, ~.07% Lead, ~.05% Iron,
Remainder Zinc
 Electrical Conductivity: 28% IACS
 Electrical Resistance: 6.2µΩ/cm
 Friction: Very low with Most metals
 Melting Point: 910oC
 Inner/Outer Diameter: 0.87”/1”
 Cost: $58.68 for 36”
Projectile
 Metal: Aluminum
 Composite: 2011
 Temper: T3
 Part #: 88615K411
 Melting point: 540oC
 Electrical Conductivity: 45% IACS
 Electrical Resistivity: 3.8µΩ/cm
 Diameter: 7/8”
 Length: ~1”
 Cost: $17.41/foot
Pneumatic Kick-start
 Avoids spot welding projectile
 Added kinetic energy
 Eliminates static friction coefficients
 Compressed Air/CO2 system
 Activated by Microcontroller post safety checks
Chassis Specs
Inner 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 Features
 Voltage sensors on rails, cap bank, & source
 Kill power if out of expected range
 EM Field Sensor
 Faraday cage if EM field great enough
 Plexiglas casing
 Keep user isolated from high voltages and short
circuited rails
Block Diagram
Capacitor
Array
Power
Supply
Rails
Inductor
Kill
Switch
LEDs
MSP430xxxx
LCD
Keypad
Microcontroller
 MSP430xxxx family
 Testing on MSP430F169
 16-bit for accurate calculation of sensor data
 Control safety logic based on sensor values
 Disconnect switches from caps to rails
 Display values on LCD
Software Engineering
 Interface with Matlab
 Import sensor data
 Statistical analysis
 Display results to user as graphs and tables
 Maintain records
PCB Elements
 Power supply
 MSP430 Family
 Debug/information LEDs
 LCD (3 or 4 rows)
 Keypad input
 Communication with sensors(A/D)
Sensor
 Measure voltage at high sample rate
 Used for analysis and safety logic
 Implementation:
 Voltage transducer
 Sample @ 10 MHz +
 Response time < 50μs
User Interface
 Basic keypad
 Input desired voltage to apply to rails
 3 or 4 line LCD on PCB
 Output sensor data and statistics
 Basic input user interface
 If time:
 Keyboard input
 Computer monitor with GUI
 Matlab sensor data analysis
Expenses
Item
# 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 Labor
Jonathan
Primary
Rail
Responsibility fabrication &
Safety
Mike
Jason
Microcontroller Power
systems &
& Safety
Safety
Schedule
“Real World” Application
 Control System for other high voltage applications
 Accelerator for fun, military, other scientific research
 Capacitor array for high current burst power systems
 Sensor to Matlab interface
Realization
 Stay under budget by getting donations
 Establish primary goals/reasonable functionality
 Operate within these
 Add incremental levels of difficulty based on time
Plan B
 Risk:
 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?