[Richard Wallace]

Originally Posted by [527]phil

... But despite which kind i build, first i need to get the boost converter working, once thats working everything else is easy to make. It'll also give me a chance to use one of those PIC microcontrollers i have

The boost converter is a fun project in its own right. Learning to build switch-mode power converters is worth the time spent. I'm a little biased here; switch-mode power converters were one of my earliest projects (after audio amplifiers) a couple dozen years ago when I was getting started in electronics.

However, if you just want to charge capacitors, a simple charging circuit using a 115VAC line cord, a full-wave rectifier, a couple of resistors (one in the 50 to 100 Ohm range in series with each capacitor for current limiting, and another in the 100,000 to 200,000 Ohm range across each capacitor to bleed off the charge when it's not in use) and a suitably rated, insulated switch for each capacitor you want to charge would do the job nicely, if you can make the coil gun work with about 170 Volts dc on each capacitor.

If you need higher voltage, or if you need to adjust the voltage to control the gun, or if you just want the fun of building a switch-mode circuit, then go on ahead with the boost converter.

Also, if you are planning on a multi-stage gun with each stage fed from its own capacitor, you will probably want to have a separate voltage measurement circuit for each capacitor so you can tell when they are charged.

Insulate all the high voltage connection points well with electrician's tape or heat shrink tubing. If you plan to demonstrate the device (and why else would you build it?) then it's a good idea to enclose everything in a non-conducting project box after you get it working. And, yeah, keep one hand in your pocket while the circuit is live.

Stay safe and have fun.