Coil Gun Group 12 Bruno Diaz and George Rosenbaum

What is a coil gun? A coil gun is a device that uses a magnetic field to launch a Ferromagnetic projectile. In our coil gun, we store high levels of charge within capacitors We discharge it through a coil We build up the charge with a 36 volt source We control the circuit with a DPDT switch and SCR. Operation works in three stages

Coil Gun schematic

Power source 4 nine volt batteries Possibly 10 volts fresh Jury-rigged equivalent for testing purposes

Power Source The source is 36V when the capacitors are charging, and 9V across the SCR gate when in the firing stage 36 volts is more than the capacitors are rated at 35 Volts, batteries sometimes say 9 volts but actually are sometimes 10 volts giving a range of 36 to 40 volts. Resistor not sufficient to drop the voltage

Zener Voltage regulator Zener diode a better solution to the voltage problem Creates opposing voltage regardless of capacitor bank charge Drops voltage to a safe 31 to 35 volts.

Current Branches Current moved through two branches and into the capacitor bank to charge it. First branch just general load Second branch controls indicator Indicator is on when charging and turns off when the opposing voltage from capacitor bank is sufficient enough

Capacitor Bank Capacitors are used to obtain high charge 8 X 4700uF capacitors with total capacitance of 37.6 mF At 31 volts the charge stored is Coulombs (Q=CV) total energy stored in capacitor bank is 18 Joules (W=C*V^2) Multisim Analysis of Capacitor charge,

SCR Thyristor The thyristor is a 4 layer semiconductor which can be logically represented with 2 BJT transistors. When the NPN bjt portion is in saturation, it forces the PNP bjt portion into saturation as well. Thyristors are used because they provide a high surge current rating. A normal switch would break.

SCR Thyristor When the voltage difference between the gate and cathode is high enough, the diode will turn on. When one diode is on/off, the other diode is in the same state. So if gate- cathode voltage isn’t high enough to turn on the diode, then current won’t flow from anode to cathode. Once the SCR is switched on, it stays on even if the trigger voltage is removed. The SCR will only switch off once the anode-cathode current reaches 0 A.

Switch The switch has three modes: – The capacitors are charging, and the SCR is off – The capacitors are not charging, and the SCR is off – The capacitor are discharging, and the SCR is on.

Coil Operation There will be a spike in impedance as the current spike goes through our coil. The current spikes for a moment as voltage drops sharply because v(t) = L(di(t)/dt), so a sharp change in voltage creates a sharp increase in current.

Coil Operation A changing current induces a magnetic current. F = (B 2 A)/(2u 0 ), where u 0 is a constant value for the permeability of air.

Building the Circuit

Works Cited "Capacitance." Hyper Physics. N.p.. Web. 26 Apr "Faraday’s Law." Hyper Physics. N.p.. Web. 26 Apr Coil Gun. < 01.pdf High Voltage Phase Control Thyristor, 40A < "Inductance." Hyper Physics. N.p.. Web. 26 Apr < astr.gsu.edu/hbase/electric/induct.html Serda, Adel, and Kenneth Smith. Microelectronic Circuits. 6th. New York: Oxford University Press, Print. "Thyristors." All About Circuits. N.p.. Web. 26 Apr