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Registered Member #1902
Joined: Fri Jan 02 2009, 07:59PM
Location: Lancaster, NY
Posts: 75
Now I have resumed construction on my table top class-E sstc I would like to find some kind of common material for a sharp breakout point to thread into the quarter inch hole on top of the former. Any suggestions? Oh and OT is steve's new QCW powered by a syncronous boost supply? Just a suggestion.
Registered Member #2628
Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627
now bringin the topic of tungsten,
I wonder personally what kind will have effects on the arc itself, for example tungsten is sold with some additives in it sometimes (lanthanated tungsten, thoriated tungsten, ceriated tungsten etc.) anyone tried any specific tungsten rod?
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Corey wrote ...
Now I have resumed construction on my table top class-E sstc I would like to find some kind of common material for a sharp breakout point to thread into the quarter inch hole on top of the former. Any suggestions? Oh and OT is steve's new QCW powered by a syncronous boost supply? Just a suggestion.
-Corey
Just a copper electrode should suffice if its thick enough. Just don't use steel as it will get much hotter and melt quicker.
See QCW thread for info on Steve's QCW coil. I believe it is a synchronous buck, although thats probably much more complicated than it needs to be. We have a couple of different designs we are working right now. One uses a simple buck topology running open loop that simply idles at some low voltage, and then ramps up according to however the PIC is programmed. Of course, you don't even need a PIC, just a simple ramp circuit fed into a comparator to get your ramped up duty cycle for the buck switch. The ramp up being triggered by your incoming interrupter (modulation) pulse.
Another simple way we are getting great results is with not even using an active power supply. Just a simple resistor-capacitor network that is triggered by your incoming pulse. In fact, its almost so simple a caveman good do it. Basically just a capacitor charging network. When the incoming modulator pulse comes in, you simply turn a single MOSFET on which dumps energy from your main DC bus cap and charges your idling capacitor supply. Its not a linear ramp, but rather exponential, but works just as well. Selection of R's and C's will determine the charge rate, available energy, etc... We're actually pursuing this one more than the buck since its much simpler, albeit with less flexibility of control, and cheaper too.
Registered Member #1902
Joined: Fri Jan 02 2009, 07:59PM
Location: Lancaster, NY
Posts: 75
Are tungsten rods even made to be 1/4 inch, it would preferably be threaded too. And about Steve's design wouldn't any type of DC bus control need some type of active snubber?
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
I had a lot of trouble finding an electrode that would stand up to long discharges in my audiomodded coil, so I ended up using a piece of tungsten that I salvaged from a large laser flashlamp (that had been cracked), which I had loosely wrapped in a piece of copper wire. The tungsten glows orange-white hot, and the copper gets quite warm, but not warm enough to melt the solder I used to attach it so I am happy
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Tungsten is great stuff for making electrodes, but it's also incredibly hard, good luck trying to cut a screw thread into it! You might be able to braze a piece to a 1/4" bolt.
Steve's QCW coil is indeed powered by a synchronous buck converter, made from a halfbridge IGBT brick.
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Materials for durable breakout point?
