Smoke Machine


2006-08-10 12:32 am

Well, I've been working on my coilgun project, or at least a subproject, as I first need to build something like a working tesla coil in order to build up the required voltages.

Behold, here is my circuit, and I absentmindedly plugged a 1N4001 into the place where a high-current diode should have been... My brother came in and watched. The diode's black casing actually cracked and some poured out in a ribbon from the crack. Amazingly, the diode still seemed to work! It seems that the silicon in the diode was capable of handling the heat for at least a small while, but the casing wasn't.


C1 is disconnected, because with it connected I was apparently getting less current through the coil. The MOSFET is on a heatsink, though it still gets quite hot, hot enough to burn me, as I found out. Funny how I also learned that heatsink compound also turns a nice cherry-blossom shade of pink when it gets hot for the first time. This is an oscillator, and it uses the miller capacitance of the MOSFET as the capacitor. This will change with the load, as I was told, but as long as my coil doesn't burn up during the run I think it's fine. R1 determines the frequency, and so the circuit can easily be tuned via POT or trimmer. With the 330k resistor I think it oscillates at somewhere from 5-10KHz. I am powering the circuit with 4 cheap lantern batteries wired in series-parallel, to give twice the voltage at twice the operating time.

The driving coil is a flat coil of something around 10 turns, and the secondary is a solenoid wound around a transparent candy tube about 1" in diameter. with something above 300 turns. I got no sparks out of the primary, with both wire points facing each other, which was disappointing, but at least I made a nice smoke machine. :)

I later replaced the diode with a one I gutted from an old amplifier PSU, and it seems to be doing well. I might post pics of my setup, if there is demand.

- keantoken