Beginnings of my first DRSSTC
Shaun, Tue May 15 2007, 02:27AMIn the thread immediately before this one "Powering up an SGTC" I posted at the end that instead of investing in new parts to make my SGTC moke powerful, I decided to take the step up to a solid-state DRSSTC. Well, just now I was browsing eBay to see approximately what this undertaking would cost me, and I saw for about $22 5200' (a mile!) of 32ga magnet wire, no bidders. End time: 7 minutes. If anyone has ever been in this situation before, you know the mentality. Of course I had to get it, so now I pretty much have to build it; I can't bear to waste money.
My major goal will be durability over all other factors (within reason). I would like to be able to run it continuously for many minutes (15+) without worrying about overhating of anything.
Even though TeslaMap is for SGTCs, I still can use it to calculate specs for various parts.
Here's what I came up with:
Secondary- 2500 turns 32awg, 22" winding length on 4" thin wall PVC
Primary- Not sure yet; is copper tube advantageous over heavy gauge stranded copper wire (which I have excess of)?
Switching- H-bridge, I'll get some nice Bricks from digikey, I want to stress everything the least amount possible.
Driver- Something well built and widely know to work well- Probably the Steve Ward driver.
Toroid- A big one, window screen method.
I know the policy here is to not have other members do your homework. I have spent many hours searching through DRSSTC design guides, a favorite is this one. But I still have a few unanswered questions, which I feel are important.
What sort of power supply do I need, and how many watts should be use for a design this size?
IS A HELICAL COIL ADVANTAGEOUS OVER A CONICAL COIL??
And finally, I have heard that you can use the mains ground as an RF ground if properly connected thru a rugged low-pass filter. Is this true, or BS? Just because the added protability would be great.
If any of these questions sound obvious or noob-ish, forgive me, this is my first Solid State coil, second overall. However, I have extensive experience with low voltage semiconductor circuits, and I've seen the driver schematics and feel like they are well within my reach.
Any help would be greatlyappreciated.
-Shaun
Re: Beginnings of my first DRSSTC
Steve Ward, Tue May 15 2007, 02:40AM
A pretty typical power supply is just a bridge rectifier and some large electrolytic capacitors. If running on 120V mains and using 600V silicon (most common scenario), you can do a voltage doubler (im sure there is a schematic for one somewhere on my site, if not let me know). Otherwise, if 240V is available, just a full wave rectifier into the caps. For something in the 4-6 foot spark range, id suggest about 400J of storage caps.
No, not really. In fact, you can probably get by fine with a flat primary if you can get the coupling up to about .18 or so.
Well, i used mains ground on my coils up to 4 foot sparks, but after that it seemed pretty dangerous. In fact, on my DRSSTC 1, when producing upward of 5 foot sparks, i saw the RF ground ARC to the mains wiring on my terminal strip! This was when i was using an RF ground point in my backyard (which was likely better than my house ground setup). So just be cautious.
Steve Ward, Tue May 15 2007, 02:40AM
What sort of power supply do I need, and how many watts should be use for a design this size?
A pretty typical power supply is just a bridge rectifier and some large electrolytic capacitors. If running on 120V mains and using 600V silicon (most common scenario), you can do a voltage doubler (im sure there is a schematic for one somewhere on my site, if not let me know). Otherwise, if 240V is available, just a full wave rectifier into the caps. For something in the 4-6 foot spark range, id suggest about 400J of storage caps.
IS A HELICAL COIL ADVANTAGEOUS OVER A CONICAL COIL??
No, not really. In fact, you can probably get by fine with a flat primary if you can get the coupling up to about .18 or so.
And finally, I have heard that you can use the mains ground as an RF ground if properly connected thru a rugged low-pass filter. Is this true, or BS? Just because the added protability would be great.
Well, i used mains ground on my coils up to 4 foot sparks, but after that it seemed pretty dangerous. In fact, on my DRSSTC 1, when producing upward of 5 foot sparks, i saw the RF ground ARC to the mains wiring on my terminal strip! This was when i was using an RF ground point in my backyard (which was likely better than my house ground setup). So just be cautious.
Re: Beginnings of my first DRSSTC
Shaun, Tue May 15 2007, 03:01AM
I already have an 8 foot copper ground rod in my lawn from the SGTC; it's good to know this will be suitable if needed. But I fully intend to try the mains ground as well (after unplugging everything else on the circuit)!
Also, when you reference a coupling of .18, is there an easy way to measure this? or is it usually calculated?
I remember reading an article on the coupling of 30 degree inverted conical versus flat spiral, and that a conical does couple better, but more is not always better with DRSSTCs, from waht I recall.
Shaun, Tue May 15 2007, 03:01AM
I already have an 8 foot copper ground rod in my lawn from the SGTC; it's good to know this will be suitable if needed. But I fully intend to try the mains ground as well (after unplugging everything else on the circuit)!
Also, when you reference a coupling of .18, is there an easy way to measure this? or is it usually calculated?
I remember reading an article on the coupling of 30 degree inverted conical versus flat spiral, and that a conical does couple better, but more is not always better with DRSSTCs, from waht I recall.
Re: Beginnings of my first DRSSTC
Steve Ward, Tue May 15 2007, 03:56AM
For DRSSTCs (and i think this actually goes for ALL TCs) is that the higher coupling produces better results, that is until insulation breakdown between the two coils.
I use JAVATC to do my calculations, and the .18 figure is based upon that program's predictions. Conical and helical primaries become more attractive in that they may be easier to shield from the sparks than a flat spiral winding.
Oh, and id suggest a tank capacitor around .3 to .4 uF at 6kV. That should allow you to figure out your primary.
Steve Ward, Tue May 15 2007, 03:56AM
For DRSSTCs (and i think this actually goes for ALL TCs) is that the higher coupling produces better results, that is until insulation breakdown between the two coils.
I use JAVATC to do my calculations, and the .18 figure is based upon that program's predictions. Conical and helical primaries become more attractive in that they may be easier to shield from the sparks than a flat spiral winding.
Oh, and id suggest a tank capacitor around .3 to .4 uF at 6kV. That should allow you to figure out your primary.
Re: Beginnings of my first DRSSTC
Shaun, Tue May 15 2007, 05:18PM
Funny coincidence, I actually have a pair of 10KVDC .5uf caps (Plastic Capacitors LK 100 504A). One should be good for this application, good thing I have two cause I don't know if they're pulse rated, and it could easily blow. The capacitance is out of the range you gave me, but I figure If anything I'll get hotter arcs. Of course, I could always series the two for .25 uf, but I'd rather be over the range than under it (and use only one cap!).
So here's what JavaTC turned out, nothing here is really set in stone yet except the secondary wire gauge. These are just specs I made up that would be easy for me to put together, and that get the k in the right range.
Units are inches.
----------------------------------------- -----------
Secondary Coil Inputs:
------------------------------------------ ----------
2.125 = Radius 1
2.125 = Radius 2
18 = Height 1
40 = Height 2
2500 = Turns
32 = Wire Awg
--------------------------------------------- -------
Primary Coil Inputs:
------------------------------------------ ----------
6 = Radius 1
6 = Radius 2
18 = Height 1
24 = Height 2
10 = Turns
0.375 = Wire Diameter
0.5 = Primary Cap (uF)
3 = Total Lead Length
0.162 = Lead Diameter
---------------------------------------- ------------
Top Load Inputs:
------------------------------------------ ----------
Toroid #1: minor=6, major=22, height=48, topload
----------------------------------------- -----------
Secondary Outputs:
----------------------------------------- -----------
83.13 kHz = Secondary Resonant Frequency
90 deg° = Angle of Secondary
22 inch = Length of Winding
113.6 inch = Turns Per Unit
0.00085 inch = Space Between Turns (edge to edge)
2781.6 ft = Length of Wire
5.18:1 = H/D Aspect Ratio
456.36 ohms = DC Resistance
60137 ohms = Forward Transfer Impedance
59766 ohms = Reactance at Resonance
0.53 lbs = Weight of Wire
114.423 mH = Les-Effective Series Inductance
108.457 mH = Lee-Equivalent Energy Inductance
120.54 mH = Ldc-Low Frequency Inductance
32.034 pF = Ces-Effective Shunt Capacitance
29.99 pF = Cee-Equivalent Energy Capacitance
44.791 pF = Cdc-Low Frequency Capacitance
10.08 mils = Skin Depth
25.262 pF = Topload Effective Capacitance
547.3 ohms = Effective AC Resistance
109 = Q
----------------------------------------------- -----
Primary Outputs:
----------------------------------------- -----------
40.15 kHz = Primary Resonant Frequency
51.7 % high = Percent Detuned
90 deg° = Angle of Primary
31.42 ft = Length of Wire
0.225 inch = Average spacing between turns (edge to edge)
3.875 inch = Primary to Secondary Clearance
31.366 µH = Ldc-Low Frequency Inductance
0.11666 µF = Cap size needed with Primary L (reference)
0.055 µH = Lead Length Inductance
356.405 µH = Lm-Mutual Inductance
0.183 k = Coupling Coefficient
5.46 = Number of half cycles for energy transfer at K
66.62 µs = Time for total energy transfer (ideal quench time)
-------------------------------------------- -------------------------------
THe only thing here that worries me is the 5.18:1 H/D ratio on the secondary. Is this acceptable, or should I move up to 6" pipe? Does it even matter that much?
btw I took my AP chemistry exam about 25 minutes ago. There's not a shred of doubt in my mind that I got a five :)
Shaun, Tue May 15 2007, 05:18PM
Funny coincidence, I actually have a pair of 10KVDC .5uf caps (Plastic Capacitors LK 100 504A). One should be good for this application, good thing I have two cause I don't know if they're pulse rated, and it could easily blow. The capacitance is out of the range you gave me, but I figure If anything I'll get hotter arcs. Of course, I could always series the two for .25 uf, but I'd rather be over the range than under it (and use only one cap!).
So here's what JavaTC turned out, nothing here is really set in stone yet except the secondary wire gauge. These are just specs I made up that would be easy for me to put together, and that get the k in the right range.
Units are inches.
----------------------------------------- -----------
Secondary Coil Inputs:
------------------------------------------ ----------
2.125 = Radius 1
2.125 = Radius 2
18 = Height 1
40 = Height 2
2500 = Turns
32 = Wire Awg
--------------------------------------------- -------
Primary Coil Inputs:
------------------------------------------ ----------
6 = Radius 1
6 = Radius 2
18 = Height 1
24 = Height 2
10 = Turns
0.375 = Wire Diameter
0.5 = Primary Cap (uF)
3 = Total Lead Length
0.162 = Lead Diameter
---------------------------------------- ------------
Top Load Inputs:
------------------------------------------ ----------
Toroid #1: minor=6, major=22, height=48, topload
----------------------------------------- -----------
Secondary Outputs:
----------------------------------------- -----------
83.13 kHz = Secondary Resonant Frequency
90 deg° = Angle of Secondary
22 inch = Length of Winding
113.6 inch = Turns Per Unit
0.00085 inch = Space Between Turns (edge to edge)
2781.6 ft = Length of Wire
5.18:1 = H/D Aspect Ratio
456.36 ohms = DC Resistance
60137 ohms = Forward Transfer Impedance
59766 ohms = Reactance at Resonance
0.53 lbs = Weight of Wire
114.423 mH = Les-Effective Series Inductance
108.457 mH = Lee-Equivalent Energy Inductance
120.54 mH = Ldc-Low Frequency Inductance
32.034 pF = Ces-Effective Shunt Capacitance
29.99 pF = Cee-Equivalent Energy Capacitance
44.791 pF = Cdc-Low Frequency Capacitance
10.08 mils = Skin Depth
25.262 pF = Topload Effective Capacitance
547.3 ohms = Effective AC Resistance
109 = Q
----------------------------------------------- -----
Primary Outputs:
----------------------------------------- -----------
40.15 kHz = Primary Resonant Frequency
51.7 % high = Percent Detuned
90 deg° = Angle of Primary
31.42 ft = Length of Wire
0.225 inch = Average spacing between turns (edge to edge)
3.875 inch = Primary to Secondary Clearance
31.366 µH = Ldc-Low Frequency Inductance
0.11666 µF = Cap size needed with Primary L (reference)
0.055 µH = Lead Length Inductance
356.405 µH = Lm-Mutual Inductance
0.183 k = Coupling Coefficient
5.46 = Number of half cycles for energy transfer at K
66.62 µs = Time for total energy transfer (ideal quench time)
-------------------------------------------- -------------------------------
THe only thing here that worries me is the 5.18:1 H/D ratio on the secondary. Is this acceptable, or should I move up to 6" pipe? Does it even matter that much?
btw I took my AP chemistry exam about 25 minutes ago. There's not a shred of doubt in my mind that I got a five :)
Re: Beginnings of my first DRSSTC
Brett Miller, Tue May 15 2007, 05:30PM
Steve,
Since, like Shaun, I am working on my first DRSSTC, I had a question regarding the bridge electrolytics. I have two 2500uf 350v Cornell Dubilier electrolytics, which would probably work great for my half bridge doubler. However, they are huge and would cramp up my lower level guts or force me to go with a larger base for my coil. I also have 4 1000uf 200v electrolytics which I got off of ebay a few months ago when I thought I was going to design something smaller. Thinking about what would happen if I screwed up the OCD or failed to achieve ZCS (at severl hundred Khz) worried me into going with the 12 x 4 31 awg secondary.
I guess my question has to do with the lower limit of energy storage for an H or half bridge bus caps. Is there a method for calculating the minimum energy you need there? I would like to be able to use caps small enough to mount them right on the half-bridge pcb, but naturally the 2500uf ones would have to be mounted off the board and wired in, like on your DRSSTC-3 and Chris Hooper's DRSSTC-1. I've looked all over the popular coiling resources and can't seem to find any insight here...I suppose I could have looked at SMPS design web sites, but I have done this before and don't recall any formulas for determining this.
Sorry for barging in on your DRSSTC thread Shaun, but perhaps this will benefit you too.
-Brett
Brett Miller, Tue May 15 2007, 05:30PM
Steve,
Since, like Shaun, I am working on my first DRSSTC, I had a question regarding the bridge electrolytics. I have two 2500uf 350v Cornell Dubilier electrolytics, which would probably work great for my half bridge doubler. However, they are huge and would cramp up my lower level guts or force me to go with a larger base for my coil. I also have 4 1000uf 200v electrolytics which I got off of ebay a few months ago when I thought I was going to design something smaller. Thinking about what would happen if I screwed up the OCD or failed to achieve ZCS (at severl hundred Khz) worried me into going with the 12 x 4 31 awg secondary.
I guess my question has to do with the lower limit of energy storage for an H or half bridge bus caps. Is there a method for calculating the minimum energy you need there? I would like to be able to use caps small enough to mount them right on the half-bridge pcb, but naturally the 2500uf ones would have to be mounted off the board and wired in, like on your DRSSTC-3 and Chris Hooper's DRSSTC-1. I've looked all over the popular coiling resources and can't seem to find any insight here...I suppose I could have looked at SMPS design web sites, but I have done this before and don't recall any formulas for determining this.
Sorry for barging in on your DRSSTC thread Shaun, but perhaps this will benefit you too.
-Brett
Re: Beginnings of my first DRSSTC
Steve Ward, Tue May 15 2007, 05:30PM
Can you get a picture of your capacitor? I will say that a DRSSTC tank cap is a pretty hard life. The HV is not the bad part really, but the high currents. And, not so much the peak current (should be less than 1kA here for sure) but the RMS currents. The RMS currents tend to be rather high, id guess around 40-50 A for a coil with 4 foot sparks running 120BPS. Its the RMS current that causes the heating, and ultimate failure of the capacitor. So figure out if its worth the risk, or if you should just buy a good MMC bank.
The H/D ratio is a little extreme in my book, but not too crazy really. If you could get 6" pipe, then it might be worth it, otherwise id suggest just making your secondary a little shorter. Of course, it will likely work just fine as is. It depends on how long you want the sparks to be i suppose.
Congrats on the AP chem exam, i suppose that means no chem for you in college?
Steve Ward, Tue May 15 2007, 05:30PM
Can you get a picture of your capacitor? I will say that a DRSSTC tank cap is a pretty hard life. The HV is not the bad part really, but the high currents. And, not so much the peak current (should be less than 1kA here for sure) but the RMS currents. The RMS currents tend to be rather high, id guess around 40-50 A for a coil with 4 foot sparks running 120BPS. Its the RMS current that causes the heating, and ultimate failure of the capacitor. So figure out if its worth the risk, or if you should just buy a good MMC bank.
The H/D ratio is a little extreme in my book, but not too crazy really. If you could get 6" pipe, then it might be worth it, otherwise id suggest just making your secondary a little shorter. Of course, it will likely work just fine as is. It depends on how long you want the sparks to be i suppose.
Congrats on the AP chem exam, i suppose that means no chem for you in college?
Re: Beginnings of my first DRSSTC
Brett Miller, Tue May 15 2007, 06:08PM
Steve and Shaun,
Ok, it is discussed in the tips for constructing the bridge inverter in Steve's design guide. I guess I have been focussing so much on reading and re-reading the driver theory section, that I had not perused the bridge tips in a while.
Size the filter caps so that they store 20-50x the intended bang energy. Thanks again Steve.
-Brett
Brett Miller, Tue May 15 2007, 06:08PM
Steve and Shaun,
Ok, it is discussed in the tips for constructing the bridge inverter in Steve's design guide. I guess I have been focussing so much on reading and re-reading the driver theory section, that I had not perused the bridge tips in a while.
Size the filter caps so that they store 20-50x the intended bang energy. Thanks again Steve.
-Brett
Re: Beginnings of my first DRSSTC
Shaun, Tue May 15 2007, 08:18PM
Wow, another weird coincidence. I have some lytics very similar to Brett's that I also got off Ebay, from when I was attempting a coilgun. I was hoping to use them in the doubler for the DRSSTC. THe attached pic shows the two types of lytics, I have 4 each of the ones on the left and right. They are Mallorys, which I'm pretty sure is a division of Cornell Dublier. The center one is the one I mentioned in an earlier post as a possible primary tank cap.
Any comments?
(BTW Brett, feel free to barge in as much as you need to, I'm in no rush)
And Steve, I think I will go to a 6 inch secondary based on your advice. The only reason I started at 4" was because I have an 8 foot section of it in my garage, left over from my first coil.
Edit: Haha...it looks like there's a tiny coil of wire sitting on top of the left cap, but its a 2 pound spool of 24 ga.
Reminds me of how my friends and I used to take pictures of people standing in someone else's hand.
Shaun, Tue May 15 2007, 08:18PM
Wow, another weird coincidence. I have some lytics very similar to Brett's that I also got off Ebay, from when I was attempting a coilgun. I was hoping to use them in the doubler for the DRSSTC. THe attached pic shows the two types of lytics, I have 4 each of the ones on the left and right. They are Mallorys, which I'm pretty sure is a division of Cornell Dublier. The center one is the one I mentioned in an earlier post as a possible primary tank cap.
Any comments?
(BTW Brett, feel free to barge in as much as you need to, I'm in no rush)
And Steve, I think I will go to a 6 inch secondary based on your advice. The only reason I started at 4" was because I have an 8 foot section of it in my garage, left over from my first coil.
Edit: Haha...it looks like there's a tiny coil of wire sitting on top of the left cap, but its a 2 pound spool of 24 ga.
Reminds me of how my friends and I used to take pictures of people standing in someone else's hand.
Re: Beginnings of my first DRSSTC
Steve Ward, Tue May 15 2007, 08:40PM
Brett: the 20-50X bang energy is a very broad range, that seemed to work well for all of my coils. If you make the lytics too small, they likely arent going to be rated for enough RMS current, and will overheat from use. I also like a good bit of energy storage so that the supply doesnt sag too much during the bang. Of course, lots of storage leads to more damage in the event of a failure, but i dont think it really matters much since its just a matter of how loud the IGBT will pop :P.
Shaun, that cap you show is definately not going to work. Its a DC filtering cap (im almost positive of this), and would probably be ok at 60hz AC, but surely not RF work and not at this current level. From what ive seen, for a DRSSTC, the MMC can be made from metalized film caps (rather than film foil) to save some money. The reason for this is, that you will generally have a few parallel strings of caps, and its the RMS currents that stress the cap bank. Metalized caps RMS rating is better per $ than foil caps. In either case, your MMC will usually well exceed the peak current requirement.
Steve Ward, Tue May 15 2007, 08:40PM
Brett: the 20-50X bang energy is a very broad range, that seemed to work well for all of my coils. If you make the lytics too small, they likely arent going to be rated for enough RMS current, and will overheat from use. I also like a good bit of energy storage so that the supply doesnt sag too much during the bang. Of course, lots of storage leads to more damage in the event of a failure, but i dont think it really matters much since its just a matter of how loud the IGBT will pop :P.
Shaun, that cap you show is definately not going to work. Its a DC filtering cap (im almost positive of this), and would probably be ok at 60hz AC, but surely not RF work and not at this current level. From what ive seen, for a DRSSTC, the MMC can be made from metalized film caps (rather than film foil) to save some money. The reason for this is, that you will generally have a few parallel strings of caps, and its the RMS currents that stress the cap bank. Metalized caps RMS rating is better per $ than foil caps. In either case, your MMC will usually well exceed the peak current requirement.
Re: Beginnings of my first DRSSTC
Shaun, Wed May 16 2007, 02:56AM
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?
Shaun, Wed May 16 2007, 02:56AM
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?
Re: Beginnings of my first DRSSTC
Brett Miller, Wed May 16 2007, 03:41AM
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?
-Brett
Brett Miller, Wed May 16 2007, 03:41AM
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?
-Brett
Re: Beginnings of my first DRSSTC
Steve Ward, Wed May 16 2007, 06:48PM
Im not sure, but id expect them to be OK.
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.
Steve Ward, Wed May 16 2007, 06:48PM
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.
Re: Beginnings of my first DRSSTC
Shaun, Thu May 17 2007, 01:16AM
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.
Shaun, Thu May 17 2007, 01:16AM
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.
Re: Beginnings of my first DRSSTC
Brett Miller, Thu May 17 2007, 07:39PM
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?
-Brett
Brett Miller, Thu May 17 2007, 07:39PM
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.
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?
-Brett
Re: Beginnings of my first DRSSTC
Shaun, Thu May 17 2007, 08:33PM
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.
Any comments?
Shaun, Thu May 17 2007, 08:33PM
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.
Any comments?
Re: Beginnings of my first DRSSTC
Brett Miller, Fri May 18 2007, 04:14AM
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.
-Brett
Brett Miller, Fri May 18 2007, 04:14AM
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.
-Brett
Re: Beginnings of my first DRSSTC
Steve Ward, Fri May 18 2007, 05:24AM
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).
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.
Steve Ward, Fri May 18 2007, 05:24AM
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.
Re: Beginnings of my first DRSSTC
Shaun, Fri May 18 2007, 12:27PM
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.
Shaun, Fri May 18 2007, 12:27PM
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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