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Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Too bad about the cap. Well, they're still fun to charge with the TV flyback and then short with a file when people arent expecting it. My neighbor thought we were lighting off firecrackers!
Anyway, I suppose I will just go ahead and make an MMC. I used metallized polypropylene caps for my SGTC's MMC, but I doubt I'll have enough left for another. It has performed reliably with proper insulation, even though it's made of more caps than usual. 98 capacitors, .015uf@1600V, wired in 7 strings of 14. However, thes are not that good for a higher capacitance, lower voltage MMC. I'm just gonna start watching Ebay and searching the electronics suppliers for good, cheap ones.
By the way, I was on your site looking at the interrupter schematic. Is Burst Mode like a type of single-shot streamer? Or a does it trigger a small number of high-speed breaks?
Registered Member #593
Joined: Tue Mar 20 2007, 12:32AM
Location:
Posts: 50
Yeah, that Plastic Capacitors 0.5uf cap that Shaun has looks similar to the oil filled caps I always see at hamfests. I saw some last February and almost bought a few for use in my VTTC's but finally decided that free Microwave Oven caps were much more compact for the same or similar specs.
For the doubler that will power my half bridge, I guess I'll just search for the biggest lytics available that will still mount easily on the PCB I have envisioned for my bridge. Once I start the actual fabrication and construction of the bridge (right after I wind my primary) I will have exact figures and dimensions. I have the heat sinks picked out and most of the small components, I just need to order the decoupling cap. I was planning on using the Aerovox 10uf film cap available from Electronic Goldmine for a few bucks...unless the GE have been proven to be tougher in DRSSTC bridge decoupling duty?
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I was planning on using the Aerovox 10uf film cap available from Electronic Goldmine for a few bucks...unless the GE have been proven to be tougher in DRSSTC bridge decoupling duty?
Im not sure, but id expect them to be OK.
By the way, I was on your site looking at the interrupter schematic. Is Burst Mode like a type of single-shot streamer? Or a does it trigger a small number of high-speed breaks?
Burst mode just gates the original oscillator ON and OFF. The effect can be really cool, and has to be experienced in person to do it justice. I can get a wide variety of effects, but basically it sends out a bunch of shots, then rests. Some cool effects are sending out bursts of really high BPS (sounds like someone is bringing down a hammer on a piece of steel "tink! tink! tink!"). This was awesome for my largest coil, as it would throw out a 10-12 foot long strike to any nearby object on almost every pulse.
Other effects can be mostly audio based. The coil can be made to sound like a mean ARSG coil as the ON and OFF periods are shortened. Other times im able to manage to tweak it just enough to have it oscillate between a pitch and its octave at ~.5 second intervals. So its a lot of fun, worth the extra timer chips and associated components.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Yes, I was always attracted to the fact that a DRSSTC can be controlled in nearly every aspect by a simple ocillator circuit, which can easily be upgraded to things like audio modulation, sound sensitive control (think spectators clapping to generate arcs), and being a low voltage circuit the danger to you is minimalized.
Registered Member #593
Joined: Tue Mar 20 2007, 12:32AM
Location:
Posts: 50
Shaun wrote ...
Yes, I was always attracted to the fact that a DRSSTC can be controlled in nearly every aspect by a simple ocillator circuit, which can easily be upgraded to things like audio modulation, sound sensitive control (think spectators clapping to generate arcs), and being a low voltage circuit the danger to you is minimalized.
Yeah, me too. The control over all aspects of a DRSSTC is attractive in many ways, especially when you think about all the opportunities for studying various aspects of coil behavior, streamer growth, etc. After getting a taste of playing with my SSTC's with a remote sheilded interrupter, I was hooked. You can change the spark colors, sounds and characteristics while the coil is running.
Steve: You mentioned to me that the primary wiring in my DRSSTC ought to be 8 or preferably 6 gauge speaker wire if I can afford it. I would certainly like to use it, regarless of cost. I'll wait and save if I have to. I noticed in an OLTC thread you and Steve C. were talking about coaxial speaker wire for PA systems...you mentioned that you use it as coax (the shield as send, and the center as return or vice versa). Is this the cable you were recommending for me, or would that not work for DRSSTC tank wiring?
I guess it would have to be used for attaching the MMC to the bridge, and from the bridge to the primary and the MMC to the primary?
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
On the subject of the remote interrupter, I've heard many different ways to go about it, such as a shielded wire connection to the coil or a fiber optic system. Would it be possible to use an RF reciever/transmitter for full remote control? I thoguht that maybe if you use one with a significantly higher frequency than the coil's (maybe 900MHz), then interference would be avoided. However, the antenna would have to be exposed, giving the possibillity of a strike. I think (not sure) that this could be avoided by shielding the assembly with a wire mesh that is small enough to catch streamer strikes, but wide enough to let the much smaller wavelength of the transmitter through.
Registered Member #593
Joined: Tue Mar 20 2007, 12:32AM
Location:
Posts: 50
Shaun,
Well for my SSTC's I use RCA coax (BNC is nice too) for the connection to the remote interrupter. Steve and others have used this method and it works great with very little headache. I would certainly utilize that for the initial tests of your DRSSTC...that is what I am going to do for sure. I like to stay simple until I have determined that every module of my system is functioning properly. This is especially important when attempting a new topology, particularly one as complex and potentially problematic as many find DRSSTC construction. Personally though, I think it really can be simple as long as you learn everything in steps and don't try to take it all in at once.
However, I'd say that once you get your DRSSTC functioning reliably while delivering sparks you are happy with, you can make the interrupter and everything else fancier. That's what I'm planning on doing. Sometimes I even make a jumpered prototype that doesn't even have a stand or certain "look" to it at all, just to prove that I can get a certain technology working. Then when I take on a bigger project, that intimidation factor has disappeared. This time I've made several VTTC projects and a couple SSTC's, all leading up to this DRSSTC I'm working on currently.
If you haven't looked at the microDRSSTC project by JimG (Jim Gage), check it out...he implemented a fiber optic connected interrupter on his coil. Very cool. Something to consider, but I would recommend starting simple because it is much easier to find where you have made a mistake in the event you wind up having to track down wiring bugs in your board. My initial interrupter is just going to be a single 555 based astable, very similar to (or exactly) what you find on Steve's site, with the timing adjusted for DRSSTC PRF and Pulse Widths.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Steve: You mentioned to me that the primary wiring in my DRSSTC ought to be 8 or preferably 6 gauge speaker wire if I can afford it. I would certainly like to use it, regarless of cost. I'll wait and save if I have to. I noticed in an OLTC thread you and Steve C. were talking about coaxial speaker wire for PA systems...you mentioned that you use it as coax (the shield as send, and the center as return or vice versa). Is this the cable you were recommending for me, or would that not work for DRSSTC tank wiring?
No, i meant standard wire, not coaxial. The coax is used for special cases where minimal inductance is required.
As to using fiber optic links between the controller and coil, all of my latest DRSSTC controllers use fiber links. I convert the fiber reciever into 5V pulse on an RCA jack so it can mate up with all my previous DRSSTCs. The added complexity isnt that much really, but the fiber cable isnt really required anyway. I used it this time specifically because im using a micro controller, and i wanted as much isolation as possible (likely overkill).
Would it be possible to use an RF reciever/transmitter for full remote control? I thoguht that maybe if you use one with a significantly higher frequency than the coil's (maybe 900MHz), then interference would be avoided. However, the antenna would have to be exposed, giving the possibillity of a strike. I think (not sure) that this could be avoided by shielding the assembly with a wire mesh that is small enough to catch streamer strikes, but wide enough to let the much smaller wavelength of the transmitter through.
I have a feeling that despite the great attenuation to the tesla's output, the electric field near the coil is still quite tremendous, and will probably mess with the radio.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
The wireless setup was really just something I was going over in my head, wondering if it would work. My first DRSSTC is probably a month or two away, and I just thought that since I have no prior experience with fiber optics, then an R/C device might work. Of course I'll still try it, despite Steve's doubts, but as Brett said "After I have sparks I'm happy with".
I have wound the secondary, and assembled the MMC so far. I plan on using 2 350V 2900uf caps in a voltage doubler for power. Next for me is assembling all the small components. That could take awhile, just to get all the proper parts.
In what manner are the feedback transformers connected to the primary coil? Just in parallel with it? By the way, the idea of using networking cable to make the GDTs is great. I would never have thought of such a simple solution.
Also, are ther any particular components that need to be of a specific type or rating in the controller/gate circuit, or are regular off-the-shelf components okay everywhere? Only because in the beginning of this thread I said I wanted everything to be very durable and reliable, and would like to know which parts should have heatsinks or a higher power rating due to excessive stress.
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Beginnings of my first DRSSTC
