Need some advice...

[What's_nitro?]

How many of you have built a coil gun???

I need some advice and/or guidance from the electrical engineers in the group. I have a pretty solid understanding of electronic design, but I often find myself second-guessing my layouts. I think having some other eyes on this would be helpful since my prototyping budget doesn't allow for many burned components...

Attached is a full schematic of the system I have in mind. I've gone over it several times trying to follow all the possible current paths and make sure there are no shorts, or any other undesired electrical activities.

The 20-30vdc supply is via an 8-cell A123 battery pack. The 300-450vdc is provided by a power inverter/voltage multiplier combo, which gets its power from the A123 pack. The "projectile sense" switch is a lever-actuated microswitch, located in the barrel ahead of the firing coil, and arms the gun when it is loaded while lighting an LED as indication. Resistor R3 is in place to keep the base of Q1 negative biased until the "fire" button is pressed. Capacitor C2 is charged to a potential of 10-18vdc, depending on the potential of C3-C5, by a voltage divider consisting of R6-R7. When the "fire" button is pressed, C1 discharges through R2 into the base of Q1, turning it on, which allows C2 to discharge into the base of Q2, which turns on, allowing C3-C5 to discharge through Q2 and L1. When the projectile has moved through L1 far enough to depress the "projectile sense" microswitch, the base of Q1 is again negative biased, turning it off. Q1 turning off then allows the base of Q2 to become negative biased once again through R5, halting the flow of current through L1. The residual EMF in L1 is shunted through D2, preventing any tug-back on the projectile and also protecting Q2 from transient voltage spikes.

At least, that's how it should work.