Transcript ppt

Lock, Stock, and Three Smoking Coils:
The Electric Musket
Ryan Eder
David Grothe
Jason Kamuda
Thomas Minor
Introduction
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Gauss Rifle

Features:
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Charge status/readiness
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Three stages
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Store previous shot records and statistics
Design Constraints
Power
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Projectile velocity vs. energy control
Weight/Portability
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Hand-held, or Jeep-mounted?
Speed/Timer resolution
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Speed/accuracy of calculation vs. overkill on I/O
Coils & Capacitors
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Coils will be made of 14-AWG copper magnet
wire
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Provide high conductance, and large force on
projectile
Concerned about weight
Tentatively three banks of 15 photo-flash
capacitors each.
All that power! How do we control
it?
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SCRs?
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Provide very high voltage isolation and very high
current.
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Can’t switch them off mid-pulse
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Exactly what we need!
No good
IGBTs
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Very fast switching time (MOS-speed)
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Not many hobbyist coil guns have used them
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Relatively new (~10 years)
All that power! How do we control
it?
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High-current diodes
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Used for inductor energy recapture
Similar to inductive kickback dissipation, but
we’re actually getting the energy back to the
capacitors
Microcontroller/LCD on a completely separate,
low-voltage circuit from separate 9V battery
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All communication goes through optocouplers
How do we store the energy in the
first place?
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Use a DC-DC converter
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9V battery input (really only 4.8V), 990V output
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@1A draw, provides 700mAh, or 42 minutes of
continuous charging
Won’t actually need continuous charging except for
boot-up
Need PWM to drive transformer
Sensors

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Want to measure velocity, estimate IGBT switch
times
Essentially, use optocoupler with light path
crossing projectile path
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Hopefully BBs ≠ Black Cats
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Want high precision for accurate reporting/control
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Need fast microcontroller clock!
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Want lots of input captures ports, need at least
one.
Program Requirements
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Program shouldn’t be too big
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Store lots of statistics
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Help with determining timing
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Interesting to user: “How well did we kill ‘em?”
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Want lots of Flash!
Single point of data can’t give velocity
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Want fast arithmetic, including multiply/divide
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Want SPI to interface with cheap LCD
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Pushbutton User Interface (PUITM) needs GPIO
Microprocessors
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Freescale MCF51QE128 Series
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50.33MHz @ 2.4-3.6V
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32-bit
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1 6-channel, 2 3-channel Input Capture/PWM, SPI
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24-channel 12-bit ADC
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71 GPIO
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FPU
Microprocessors
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Microchip PIC32MX Family
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80MHz @ 2.3V-3.6V
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32-bit
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5 Input Capture, PWM, SPI
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16-channel 10-bit ADC
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Unknown GPIO, 100-pinout
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No FPU
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Single-clock multiply, fast divide
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Better support?