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