inportb

A railgun needs a pretty beefy power supply that’s able to dump loads of current across the rails. Trying to keep costs low, I decided to borrow the charging circuit of a disposable camera. I removed the capacitor, xenon flash lamp, and a bunch of nonessential parts. Then I soldered on some switches, resoldered the indicator LED onto longer wires, and added alligator clips that will lead to the capacitor bank. Obviously, the capacitors are also to come from disposable cameras.

Here’re some pictures.

This is the front side of the circuit board. There’s nothing interesting to see here, except that the switched-mode supply is working and that there is no load. The voltage across the alligator clip terminals is about 330V.

This is the back, where all the traces are visible. A lit green LED across the output terminals shows that there is, indeed, output. The high-pitched noise emitted by the circuit is indicative of the high frequency switching and the red LED is off, indicating a low voltage condition caused by the load at the output.

Here, the whole setup is positioned cozily in a pipet tip box. As can be seen, the capacitor bank hasn’t been constructed yet, but there’s plenty of room in the box for lots of power. 4 capacitors should be plenty for now. That’s about 17.5J.

The capacitors are connected in parallel and to the output using thick custom wiring. The wiring is extended beyond the box and terminated with bigger alligator clips. These will clip onto the rails, for a hot rail design. The lower pitch shows that the capacitive load greatly reduces the operating frequency.

Everything fits neatly into the box. The lid would have to be notched on the side for the wires.