Sigurthr
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- Dec 11, 2011
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EVR's coilwinder is prone to breakdowns too so availability was spotty last I looked. They'll be straight up with you about it though... no taking orders when they can't supply it quickly.
I have a 12" (damaged from several moves) secondary from a SRSG coil I made around 15 years ago, but if I remember it's got at least 18 AWG wire and was at close to 100kHz with a big aluminum dryer duct toroid. I would like to keep the frequency of this coil low both for the benefit of the slow IGBTs and to let me use the relatively big tank cap and still have at least 4 or 5 turns of primary.
what determines the power? The driver?
For example, in a SGTC you have the NSTs, Rotary gap/ static gap. Those determine power---but on a solid state TC you have one Transformer, a step down to 2A {in your design}.
"When building the Gate transformer do I need a signal generator?"
Resonant frequency determines arc length per kW (longer streamer the lower the frequency), some of the heating in the bridge (lower frequency is less heating), some of the load on the logic controller / driver (lower freq, the less load), and most importantly the physical dimensions of the secondary. Yes, 300Khz is reasonable, but I would recommend you aim for around half that for best bang/buck when size isn't a factor."How do you choose a resonant frequency? Is 300KHz reasonable."
A coil's sound is determined by the RF envelope, which is determined by operational mode (CW/Interrupted) and interrupter specs (PW and PRF). CW on well filtered DC is nearly silent, with only a lowly audible hiss ("shhhhhhhhhh") sound. Poor DC filtering or no filtering causes a very loud Buzz at the mains-rectifier frequency and many, many harmonics. It will sound like a harsh "BRRRRRRRR" tone. Interrupted mode coils vary greatly in volume and tonal character based on the specifics of their pulse width and pulse rep frequency. A shorter duration ON pulse has more harmonic content and thus sounds brighter, where as a longer ON pulse close to 50% duty sounds duller and warmer. Even if average power draw of the coil is continuous through the PRF range, the volume will chance because we humans perceive sound volume nonlinearly with respect to frequency."I would like a TC that doesn't sound like its sputtering. How do I pick that?"
555 timers are far too unreliable and imprecise for use in the actual logic controller / driver. They were originally used with a feedback system as an oscillation starter, which ironically does absolutely nothing at all when used with an interrupter, as the interrupter does this role flawlessly. They can still be used for an interrupter though. When used on a CW coil (when not used for interruption) it causes more problems than it is worth because the idea was to provide a signal that should get overridden when real feedback from the coil running takes place. The problem is that how do you ensure it gets overridden and it doesn't override the feedback signal? There's no good answer, and likewise those coils never ran reliably. CW coils without an interrupter still require an oscillation starter sometimes. It really isn't an issue though as it only requires one switch and a resistor OR a change in startup procedure for the coil. There's a whole section on it in my USSTCC unified data file, and it is on the main schematic."I noticed you omitted a 555 timer from your design."
and"Now let me understand some components, I have decided to use your logic board.
What exact piece of the puzzle does this include? What other components do I need to design and build myself. "
"I will need my own inverter correct? I will need to rectify the ac current coming from my variac.
Your listed step down transformers, are those the only ones I need? 2A step downs?"
Re: Arduino; easy as pie, really. You pick up an Arduino board, install the drivers and IDE (operating) program on any windows pc, I email you the code, you copy paste it into the IDE, plug in the Arduino to usb, hit upload, done. Then it's just a matter of attaching two 25k pots, a resistor, and the fiber optic transmitter. The F.O. receiver connects right into the USSTCC expansion port. Fiber runs between the two and just inserts in the F.O. parts. High end interrupter completed and installed.I've never used an arduino before, whole new can of worms.
Arctic alumina works, but only in conjunction with silpads, not instead of; it can't withstand the high voltages reliably.Can I use thermal paste like arctic alumina instead of sil-pads?
While some people swear by it, it isn't safe and doesn't provide very good performance to do this without at least carefully checking the mains earth wiring on the electrical branch you'll be using and adding RF balancing nodes to that mains branch. You place correctly rated class-Y and class-X capacitors between Line and Earth (Y), Neutral and Earth (Y), and between Line and Neutral (X) which allows RF to have an equal potential across the three conductors, essentially allowing any common mode filter to keep the RF out of where it shouldn't be. One of these nodes should be placed directly at where the coil gets plugged in, and one should be placed at where any sensitive equipment is to be plugged in. You should still unplug any equipment you can't afford to replace. This is still second rate compared to a proper RF earth ground line.Can I just ground the TC to mains earth at the socket?
It's a well known and documented flaw in the using of the 4046PLL for SSTCs. It's finicky as hell and sometimes you have to adjust the lock range and middle point while the coil is running just to get it going again. Make sure none of the coil's surroundings have changed too, as this will change the loaded resonant frequency of the secondary. Likewise, the resonance point changes with operating voltage, so mind that as well.My 4046PLL based SSTC isn't behaving
Don't use a parallel resistor in the secondary of the feedback transformer; this makes it a CT current transformer, and SSTCs use in-phase feedback, not 90deg shifted feedback like DRSSTCs. Remove that resistor and place a roughly 10-100k one in series with the secondary side to make it a VT (voltage transformer), then feed that in to the antenna in connection. If you ground the opposite terminal of the VT/CT secondary it forms a DC short which prevents startup oscillation (normally achieved by noise) without manually pulling the Enable line on the UCCs (modulation inputs) to Vcc. So leave the other terminal of the VT floating or use a capacitor to tie it to ground. Or you can use an interrupter or a momentary push button switch to ping the enable circuit. There's a schematic in my USSTCC files showing it.My CT feedback isn't working, and I've tried reversing polarities!