ArcAttack! Tesla Gun
Steve Ward, Mon Jun 18 2012, 07:26PMHi Guys,
Recently got a project running here thats been a lot of fun. Well, asfun as fiddling with electronics stuff gets... I think this one certainly pushes the state of the art in terms of tesla coils driven by electronics! I'll cut to the chase with a link to some pictures of the device:
See more here:
Where to begin...
Essentially its a DRSSTC that runs extra long pulses to grow sparks at a low voltage of about 55kV pk. I believe the reason the sparks stay pretty straight instead of splitting is that the low voltage allows growth only with negative coronas, which have been shown to make branchless sparks, whereas positive coronas tend to branch. But this is merely my speculation! I've not seen any research on spark development under these conditions (~400khz).
In order to maximally control the straightness of the sparks, the electronics driving the primary circuit are fairly sophisticated. Essentially im using a "phase shifted full bridge", where 1 leg of the AC output is perfectly in phase with the primary current (so it experiences wonderful zero current switching), but the other leg of the AC output is phase shifted, which essentially controls the drive voltage. If the 2 AC legs are 0 degrees phase, then the effective output voltage (differential mode) is zero. If the 2 AC legs are 180 degrees, then the entire 395V is applied to the primary circuit. So what happens is the phase is "ramped" over a period of about 17mS in order to gradually drive more and more power into the coil. This allows for growing long straight sparks that do not branch. If the voltage (or phase) is ramped too quickly, the sparks become very forked and jagged, forming multiple branches in 1 shot. This parameter is of course tweakable during operation
.The bridges themselves utilize some cheap little IGBTs (FGH60N60SMD). Each bridge has been tested to 60A peak, hard switched (due to the phase shifted bridge control) for 17mS pulse durations at 400khz. The calculated thermal rise for the die is 52*C during such a pulse. Luckily real operation is not this harsh.
The output of 2 bridges (operating synchronously) is combined through a pair of transformers, with the secondary windings in series. Each transformer is wound 6:3, so with 2 combined, its a 1:1 ratio. The reason for doing this is 1) i can ground one end of the primary now, and 2) it absolutely forces equal current sharing between the 2 H-bridges.
Power is derived from a 22.2V 5000mAHr LiPo battery, the type used for RC helicopters. It only lasts for about 8 minutes of continuous fun as the DC-DC converter uses about 700W. The DC-DC conversion itself is a resonant type converter used very commonly for capacitor charging supplies, as its short-circuit tolerant. The DC bus for the bridges is then 395VDC with 20,000uF of storage capacity. One spark eats up 200-250 Joules of this capacitors energy, so even 20k uF is a bit insufficient, the DC voltage drops by about 30V at the end of the 17mS burst.
Another interesting feature of this system is a secondary MMC. That is, there is a string of 72 x 1.2nF 700VAC capacitors INSIDE of the secondary coil. This capacitor adds about 17pF to the coil. There are a few reasons for this. 1) due to the gigantic streamers this thing produces, detuning is a serious issue, so the coil needs to have a pretty decent amount of self capacitance. 2) more Csec drops the impedance of the coil, which seems to improve spark growth behavior. 3) adding more energy storage to the secondary coil means slightly less circulating current in the primary. The way i think of it is that the system Q probably stays about the same, but since there is more energy in the secondary, there is less stored in the primary. This capacitor also provides convenient measurement of the toroid voltage by measuring the current through this capacitor only. This is where i obtained the 55kV number, which is in good agreement with previous direct HV measurement of my last QCW system using a Jennings HV vacuum cap divider. So indeed, the voltage is low.
The primary coil is wound with home-made Litz wire. 4 bundles of 4 strands of 24awg were twisted such that each strand sees the outside equally. Its important to do this, otherwise strands that remain burried inside the bundle will not carry their share of current. This is more surface area than 1/4" copper tubing at a fraction of the size and weight. Only needed about 18 feet of the litz, so it wasnt a big deal to make it using a drill with a jig.
Grounding for the system is questionable! To be totally un-tethered, i have a pair of shoes with steel mesh on the bottom for contact with the floor (dont stand on anything flammable!). My body is charged to a few kV with the 2.5A of secondary ground current. Generally, though, i prefer to add an additional connection to mains ground. The current into mains ground is about 1.5A, meaning my body capacitance is still seeing about 1A in this condition. I'm uncertain of the effects of this current through my body (it must primarily go through my right arm, which is gripping the conductive gun grip which is the only connection between me and the electronics). Anyone have any research on RF currents in the human body? People expose themselves to pretty similar fields when playing with SSTCs and VTTCs, just being up close to the secondary coil must induce quite a bit of current in
them (according to the mutual capacitance between the person and the TC).
Well, im sure i forgot to describe certain aspects of the project, so ask questions if you like.
EDIT: I should have mentioned that my shoes have wires to connect the steel mesh to the electronics ground. My body only carries capacitive (displacement) current due to my physical location near a HVRF voltage source.
Re: ArcAttack! Tesla Gun
zilipoper, Mon Jun 18 2012, 09:25PM
heh heh finally someone did it!
I have the same there is a Project portable tube coil (VTTC) but I'm too lazy to build it
here's the spark in the not portable version
spark 350 Joules capacitor 7KV 16uF
zilipoper, Mon Jun 18 2012, 09:25PM
heh heh finally someone did it!
I have the same there is a Project portable tube coil (VTTC) but I'm too lazy to build it
here's the spark in the not portable version
spark 350 Joules capacitor 7KV 16uF
Re: ArcAttack! Tesla Gun
Dr. ISOTOP, Mon Jun 18 2012, 10:03PM
WOW!
So I guess this is the evolution of the QCW - phase shift control eliminates the huge DC-DC converter that feeds the bridge.
Are you doing any kind of regulation, or does the "bus modulation" (which is kind of a stretch since the bus voltage stays constant) just run open-loop?
It's amazing that you can get such sparks with only 60A...does your regular QCW do that? How long are the sparks?
Dr. ISOTOP, Mon Jun 18 2012, 10:03PM
WOW!
So I guess this is the evolution of the QCW - phase shift control eliminates the huge DC-DC converter that feeds the bridge.
Are you doing any kind of regulation, or does the "bus modulation" (which is kind of a stretch since the bus voltage stays constant) just run open-loop?
It's amazing that you can get such sparks with only 60A...does your regular QCW do that? How long are the sparks?
Re: ArcAttack! Tesla Gun
Sulaiman, Mon Jun 18 2012, 10:23PM
That is truly awesome !
I think we all want one.
"I'm uncertain of the effects of this current through my body (it must primarily go through my right arm, which is gripping the conductive gun grip which is the only connection between me and the electronics). Anyone have any research on RF currents in the human body?"
Purely anecdotal;
a colleague at work used to be a technician/engineer
servicing amateur radio stuff at a famous specialist retailer,
there were many 'silent key' sales
...due to neck, throat, facial etc. cancers of the right side
- where hand held antennas were used.
Probably worth running a wire from the gun directly down to earth
/ the mesh shoes ..... better safe than sorry.
Sulaiman, Mon Jun 18 2012, 10:23PM
That is truly awesome !
I think we all want one.
"I'm uncertain of the effects of this current through my body (it must primarily go through my right arm, which is gripping the conductive gun grip which is the only connection between me and the electronics). Anyone have any research on RF currents in the human body?"
Purely anecdotal;
a colleague at work used to be a technician/engineer
servicing amateur radio stuff at a famous specialist retailer,
there were many 'silent key' sales
...due to neck, throat, facial etc. cancers of the right side
- where hand held antennas were used.
Probably worth running a wire from the gun directly down to earth
/ the mesh shoes ..... better safe than sorry.
Re: ArcAttack! Tesla Gun
Steve Ward, Mon Jun 18 2012, 10:31PM
Correct, you just have to account for the extra turn off loss (the turn on loss is zero, however, as its ZVS naturally). The FGH60N60SMD has very good turn off characteristics, and handles hard switch-off at 60A without problems. I looked at adding a turn off snubber, but it didnt seem necessary, and would restrict how close to 180* phase i could get.
I tried to close the loop in my micro controller, but could not stablize it (i needed to add some loop phase but never got time to try this out). It runs open loop for now, which seems to be fine. I even thought to compensate for the power factor of the phase shift bridge, but i dont think its that critical, so the phase is a linear ramp for now.
Ive recorded up to 56" sparks with 100Apk in the primary (so 50Apk per bridge). Adding the MMC to the secondary not only improved spark length by about 10" (compared to a higher inductance coil, with only a toroid), but dropped the primary current from ~120A to 100A. I also tested 2 MMC caps inside there for 33pF, it seemed to perform about the same, so i decided to keep it with just 1 MMC and have the other as a spare.
My previous QCW system made longer sparks, but used more current too. My best setup could do 65" sparks with about 140Apk in the primary, using a 16" toroid to keep the coil impedance down, and help steer the sparks.
Steve Ward, Mon Jun 18 2012, 10:31PM
So I guess this is the evolution of the QCW - phase shift control eliminates the huge DC-DC converter that feeds the bridge.
Correct, you just have to account for the extra turn off loss (the turn on loss is zero, however, as its ZVS naturally). The FGH60N60SMD has very good turn off characteristics, and handles hard switch-off at 60A without problems. I looked at adding a turn off snubber, but it didnt seem necessary, and would restrict how close to 180* phase i could get.
Are you doing any kind of regulation, or does the "bus modulation" (which is kind of a stretch since the bus voltage stays constant) just run open-loop?
I tried to close the loop in my micro controller, but could not stablize it (i needed to add some loop phase but never got time to try this out). It runs open loop for now, which seems to be fine. I even thought to compensate for the power factor of the phase shift bridge, but i dont think its that critical, so the phase is a linear ramp for now.
It's amazing that you can get such sparks with only 60A...does your regular QCW do that? How long are the sparks?
Ive recorded up to 56" sparks with 100Apk in the primary (so 50Apk per bridge). Adding the MMC to the secondary not only improved spark length by about 10" (compared to a higher inductance coil, with only a toroid), but dropped the primary current from ~120A to 100A. I also tested 2 MMC caps inside there for 33pF, it seemed to perform about the same, so i decided to keep it with just 1 MMC and have the other as a spare.
My previous QCW system made longer sparks, but used more current too. My best setup could do 65" sparks with about 140Apk in the primary, using a 16" toroid to keep the coil impedance down, and help steer the sparks.
Re: ArcAttack! Tesla Gun
plazmatron, Mon Jun 18 2012, 11:24PM
As usual, amazing work!
This particular part interests me:
Is there any reason why this couldn't be done on an ordinary DRSSTC?
The reason I ask, is that for very small coils, it seems you could easily drop the fres to something a little more manageable, using a string of caps as well as a topload.
Les
plazmatron, Mon Jun 18 2012, 11:24PM
As usual, amazing work!
This particular part interests me:
Steve Ward wrote ...
Another interesting feature of this system is a secondary MMC. That is, there is a string of 72 x 1.2nF 700VAC capacitors INSIDE of the secondary coil. This capacitor adds about 17pF to the coil. There are a few reasons for this. 1) due to the gigantic streamers this thing produces, detuning is a serious issue, so the coil needs to have a pretty decent amount of self capacitance. 2) more Csec drops the impedance of the coil, which seems to improve spark growth behavior. 3) adding more energy storage to the secondary coil means slightly less circulating current in the primary. The way i think of it is that the system Q probably stays about the same, but since there is more energy in the secondary, there is less stored in the primary. This capacitor also provides convenient measurement of the toroid voltage by measuring the current through this capacitor only.
Another interesting feature of this system is a secondary MMC. That is, there is a string of 72 x 1.2nF 700VAC capacitors INSIDE of the secondary coil. This capacitor adds about 17pF to the coil. There are a few reasons for this. 1) due to the gigantic streamers this thing produces, detuning is a serious issue, so the coil needs to have a pretty decent amount of self capacitance. 2) more Csec drops the impedance of the coil, which seems to improve spark growth behavior. 3) adding more energy storage to the secondary coil means slightly less circulating current in the primary. The way i think of it is that the system Q probably stays about the same, but since there is more energy in the secondary, there is less stored in the primary. This capacitor also provides convenient measurement of the toroid voltage by measuring the current through this capacitor only.
Is there any reason why this couldn't be done on an ordinary DRSSTC?
The reason I ask, is that for very small coils, it seems you could easily drop the fres to something a little more manageable, using a string of caps as well as a topload.
Les
Re: ArcAttack! Tesla Gun
Steve Ward, Tue Jun 19 2012, 12:30AM
Yes, these wires already exist. There is just the unavoidable issue of mutual capacitance between me and the tesla coil, my body will always be part of the local environment, so i will always have some current going through me.
Your radio technician story is pretty scary. I probably want to limit my exposure as much as possible.
I see no reason why not. You just need a lot more caps in series as the top voltage for a typical DRSSTC is much higher. Keeping the string of caps inside the secondary coil is important so that its got proper field grading around the caps. If you tried to make the MMC external to the secondary, designing it to not break down would be much harder i think. Its probably also a good idea to pot the thing, but ive left mine unpotted for now.
I havent experimented with lowering the impedance of a "typical" DRSSTC secondary, maybe there is some benefit.
Steve Ward, Tue Jun 19 2012, 12:30AM
Probably worth running a wire from the gun directly down to earth
/ the mesh shoes ..... better safe than sorry.
Yes, these wires already exist. There is just the unavoidable issue of mutual capacitance between me and the tesla coil, my body will always be part of the local environment, so i will always have some current going through me.
Your radio technician story is pretty scary. I probably want to limit my exposure as much as possible.
Is there any reason why this couldn't be done on an ordinary DRSSTC?
The reason I ask, is that for very small coils, it seems you could easily drop the fres to something a little more manageable, using a string of caps as well as a topload.
Les
I see no reason why not. You just need a lot more caps in series as the top voltage for a typical DRSSTC is much higher. Keeping the string of caps inside the secondary coil is important so that its got proper field grading around the caps. If you tried to make the MMC external to the secondary, designing it to not break down would be much harder i think. Its probably also a good idea to pot the thing, but ive left mine unpotted for now.
I havent experimented with lowering the impedance of a "typical" DRSSTC secondary, maybe there is some benefit.
Re: ArcAttack! Tesla Gun
Adam Munich, Tue Jun 19 2012, 03:23AM
This phase shifting idea is rather clever, care to share any more details on how it was accomplished?
Adam Munich, Tue Jun 19 2012, 03:23AM
This phase shifting idea is rather clever, care to share any more details on how it was accomplished?
Re: ArcAttack! Tesla Gun
Steve Ward, Tue Jun 19 2012, 05:44AM
Im sure theres probably an easier way, but mine involved an atmel Xmega16A4 micro controller, a Xillinx XC9536 CPLD, and some ultrafast comparators and a few other little bits.
There is the usual predictor zero cross detector, which feeds into the CPLD.
The CPLD generates a trigger (about 100nS long) every time the zero cross detector transitions. This trigger discharges the capacitor of a PWM ramp generator.
The PWM ramp starts ramping up right after each zero cross detection. The ramp is fed into another ultrafast comparator along with a reference voltage generated by the xmega's DAC (this voltage sets the PWM duty cycle, or phase, essentially). The output of this PWM comparator is fed back into the CPLD.
From here the CPLD has both the zero phase signal from the prediktor, and a PWM'd version of it. Theres a bit of logic to spit these signals out to the gate drivers. Essentially all the IGBT turn on events are synchronized, just that the turn off of one half bridge is variable and early (this is what the PWM stuff was all for). This is very similar but different to a true phase shifted H-bridge, but the operation is exactly the same due to the nature of the load.
Because the load is inductive, turning off early causes the output voltage to commutate (as you forward bias the freewheeling diode) so that the opposing IGBT turns on with zero voltage across it (current transitions from wheeling diode to IGBT upon current reversal). This is often called "class DE" i believe. For this reason, i actually make all the IGBTs turn off at least ~150nS before the actual current zero crossing, so that there is sufficient load current to commutate the output voltage and provide ZVS. This is mainly because these IGBTs are more efficient at turning off than turning on! It also eliminates any forced diode recovery, so the switching waveforms are quite clean, even when hard switching 50A.
The other useful thing i implemented was having the micro-controller start the coil oscillating. The micro spits out 4 to 5 cycles at 400khz to drive the bridge, before giving the command to the CPLD to switch over to the feedback input. This greatly improves the reliability of starting the system at low supply voltages, AND allows some control into biasing what pole/mode the coil operates at (this can be problematic at some tunings).
The Xmega performs over-current limiting and generates the long-term ramp for spark growth.
If people really want to see schematics and code, i suppose i can post it, but its probably only useful if you are really serious about building your own. Its a much higher level of complexity compared to the old "universal driver".
Steve Ward, Tue Jun 19 2012, 05:44AM
This phase shifting idea is rather clever, care to share any more details on how it was accomplished?
Im sure theres probably an easier way, but mine involved an atmel Xmega16A4 micro controller, a Xillinx XC9536 CPLD, and some ultrafast comparators and a few other little bits.
There is the usual predictor zero cross detector, which feeds into the CPLD.
The CPLD generates a trigger (about 100nS long) every time the zero cross detector transitions. This trigger discharges the capacitor of a PWM ramp generator.
The PWM ramp starts ramping up right after each zero cross detection. The ramp is fed into another ultrafast comparator along with a reference voltage generated by the xmega's DAC (this voltage sets the PWM duty cycle, or phase, essentially). The output of this PWM comparator is fed back into the CPLD.
From here the CPLD has both the zero phase signal from the prediktor, and a PWM'd version of it. Theres a bit of logic to spit these signals out to the gate drivers. Essentially all the IGBT turn on events are synchronized, just that the turn off of one half bridge is variable and early (this is what the PWM stuff was all for). This is very similar but different to a true phase shifted H-bridge, but the operation is exactly the same due to the nature of the load.
Because the load is inductive, turning off early causes the output voltage to commutate (as you forward bias the freewheeling diode) so that the opposing IGBT turns on with zero voltage across it (current transitions from wheeling diode to IGBT upon current reversal). This is often called "class DE" i believe. For this reason, i actually make all the IGBTs turn off at least ~150nS before the actual current zero crossing, so that there is sufficient load current to commutate the output voltage and provide ZVS. This is mainly because these IGBTs are more efficient at turning off than turning on! It also eliminates any forced diode recovery, so the switching waveforms are quite clean, even when hard switching 50A.
The other useful thing i implemented was having the micro-controller start the coil oscillating. The micro spits out 4 to 5 cycles at 400khz to drive the bridge, before giving the command to the CPLD to switch over to the feedback input. This greatly improves the reliability of starting the system at low supply voltages, AND allows some control into biasing what pole/mode the coil operates at (this can be problematic at some tunings).
The Xmega performs over-current limiting and generates the long-term ramp for spark growth.
If people really want to see schematics and code, i suppose i can post it, but its probably only useful if you are really serious about building your own. Its a much higher level of complexity compared to the old "universal driver".
Re: ArcAttack! Tesla Gun
Steve Conner, Tue Jun 19 2012, 06:56AM
That's awesome!
I bet the capacitors inside the secondary coil are really to hit the zombies harder.
I'm interested in the transformer combining scheme, because there's no reason (that I can see) to stop at two bridges. What did you use for DC block capacitors on the primary side?
I don't believe the radio ham cancer story. Every old radio ham I've known was also a heavy smoker and chronic breather of solder fumes.
Steve Conner, Tue Jun 19 2012, 06:56AM
That's awesome!
I bet the capacitors inside the secondary coil are really to hit the zombies harder.I'm interested in the transformer combining scheme, because there's no reason (that I can see) to stop at two bridges. What did you use for DC block capacitors on the primary side?
I don't believe the radio ham cancer story. Every old radio ham I've known was also a heavy smoker and chronic breather of solder fumes.
Re: ArcAttack! Tesla Gun
Wolfram, Tue Jun 19 2012, 08:01AM
This is easily the most impressive project I've seen here.
You've provided a lot of useful info, and I'm especially impressed by all the new tricks and techniques you've incoroprated into it.
Even though you've detailed the most important bits, I would be very interested in having a look at the code and the schematics for some inspiration if I get around to doing a similar project. It's extremely tempting, especially considering that I already have all the major parts, but I'm usually very slow on completing big projects.
Wolfram, Tue Jun 19 2012, 08:01AM
This is easily the most impressive project I've seen here.
You've provided a lot of useful info, and I'm especially impressed by all the new tricks and techniques you've incoroprated into it.
Even though you've detailed the most important bits, I would be very interested in having a look at the code and the schematics for some inspiration if I get around to doing a similar project. It's extremely tempting, especially considering that I already have all the major parts, but I'm usually very slow on completing big projects.
Re: ArcAttack! Tesla Gun
Steve Ward, Tue Jun 19 2012, 08:50AM
Why yes, of course there is no reason to stop at 2, in fact i had originally planned on using 4 bridges. Ultimately, 2 bridges were enough to exceed the capability of my battery and power system, so i stopped at 2. I use a .68uF 1200V snubber cap for the DC blockers. The transformers dont even have to be all that great either, a little leakage inductance just adds to the primary L. I found that lowering the coupling helped keep the sparks straighter anyway, so if i ever made another one, the primary wouldnt be as tall.
I think if i make another one, im just gonna drive the TC with MOSFETs at ~130VDC with 6 of those LiPo's in series. That way there is no stupid DC converter to impede things. With the transformers, you can match the low voltage bridges to whatever coil setup you have. Id probably also go water cooled so that you could possibly use the 12kW of power available from such a battery... well until some other components melt .
Cool, i'll see about compiling it into some useful form. I have no doubt someone could replicate my work, or even make it better. Id just have to make the warning that with a system this complex, troubleshooting really requires you know your stuff. But, i guess ive de-bugged all the code and such, so any problems should just be due to assembly mistakes or something.
Does anyone else on this forum have a serious interest in building a QCW coil?
Steve Ward, Tue Jun 19 2012, 08:50AM
I'm interested in the transformer combining scheme, because there's no reason (that I can see) to stop at two bridges. What did you use for DC block capacitors on the primary side?
Why yes, of course there is no reason to stop at 2, in fact i had originally planned on using 4 bridges. Ultimately, 2 bridges were enough to exceed the capability of my battery and power system, so i stopped at 2. I use a .68uF 1200V snubber cap for the DC blockers. The transformers dont even have to be all that great either, a little leakage inductance just adds to the primary L. I found that lowering the coupling helped keep the sparks straighter anyway, so if i ever made another one, the primary wouldnt be as tall.
I think if i make another one, im just gonna drive the TC with MOSFETs at ~130VDC with 6 of those LiPo's in series. That way there is no stupid DC converter to impede things
. With the transformers, you can match the low voltage bridges to whatever coil setup you have. Id probably also go water cooled so that you could possibly use the 12kW of power available from such a battery... well until some other components melt .Even though you've detailed the most important bits, I would be very interested in having a look at the code and the schematics for some inspiration if I get around to doing a similar project. It's extremely tempting, especially considering that I already have all the major parts, but I'm usually very slow on completing big projects.
Cool, i'll see about compiling it into some useful form. I have no doubt someone could replicate my work, or even make it better. Id just have to make the warning that with a system this complex, troubleshooting really requires you know your stuff. But, i guess ive de-bugged all the code and such, so any problems should just be due to assembly mistakes or something.
Does anyone else on this forum have a serious interest in building a QCW coil?
Re: ArcAttack! Tesla Gun
Steve Conner, Tue Jun 19 2012, 09:40AM
Me, me! :D
I'm rather intrigued by the idea of running directly off batteries. That would have been a joke when I started solid-state coiling, but the power and energy density of Lipos gets higher all the time. Maybe with direct battery power the system could be made small enough for a handheld "Tesla saber".
I also have a long-term project to make an all-digital Tesla coil controller on a FPGA (and a fiber optic multiplexed data format to go with it) and am looking for collaborators.
Steve Conner, Tue Jun 19 2012, 09:40AM
Me, me! :D
I'm rather intrigued by the idea of running directly off batteries. That would have been a joke when I started solid-state coiling, but the power and energy density of Lipos gets higher all the time. Maybe with direct battery power the system could be made small enough for a handheld "Tesla saber".
I also have a long-term project to make an all-digital Tesla coil controller on a FPGA (and a fiber optic multiplexed data format to go with it) and am looking for collaborators.
Re: ArcAttack! Tesla Gun
Dr. ISOTOP, Tue Jun 19 2012, 11:23AM
And me!
I have most of a giant QCW bus modulator sitting right here, though I fear phase-shift modulation makes it completely obsolete
How big is your transformer? Something capable of handling 120A peak must be quite bulky (though the 400 KHz operation helps handle that I suppose).
Dr. ISOTOP, Tue Jun 19 2012, 11:23AM
And me!
I have most of a giant QCW bus modulator sitting right here, though I fear phase-shift modulation makes it completely obsolete
How big is your transformer? Something capable of handling 120A peak must be quite bulky (though the 400 KHz operation helps handle that I suppose).
Re: ArcAttack! Tesla Gun
Dr. Drone, Tue Jun 19 2012, 05:07PM
Dr. Drone, Tue Jun 19 2012, 05:07PM
Re: ArcAttack! Tesla Gun
Steve Conner, Tue Jun 19 2012, 06:12PM
Sorry, regular guns might be more effective at killing things, but for sheer geek points, Steve's Tesla gun is untouchable.
Steve Conner, Tue Jun 19 2012, 06:12PM
Sorry, regular guns might be more effective at killing things, but for sheer geek points, Steve's Tesla gun is untouchable.
Re: ArcAttack! Tesla Gun
Dr. Drone, Tue Jun 19 2012, 06:57PM
Dr. Drone, Tue Jun 19 2012, 06:57PM
Re: ArcAttack! Tesla Gun
Killa-X, Tue Jun 19 2012, 07:04PM
Wish I had the money to build one of my own! Let alone the ability to make a QCW... Steps. Slowly, maybe one day...
Love it though! Nice job Steve
Killa-X, Tue Jun 19 2012, 07:04PM
Wish I had the money to build one of my own! Let alone the ability to make a QCW... Steps. Slowly, maybe one day...
Love it though! Nice job Steve
Re: ArcAttack! Tesla Gun
Steve Ward, Tue Jun 19 2012, 08:34PM
I can see where Dr Spark is coming from, there is nothing quite like shooting a real gun.
Anyway, here's some design files (ehhh, minus the PCB layouts for now):
The cores are about 2.5"x2.5"x1.25". They are in fact a lot bigger than they need to be, since i had plenty of room to fit the wire on the core with lots of space left. I mainly used these because i didnt have enough of anything smaller. The output (120A side) is wound with 10awg, and the input (60A) is wound with 12awg. With my low duty cycles, they do not warm up at all. For a real, mains powered thing, you'd probably have to use bigger copper, preferably some litz wire i think.
I guess for such a project to work out, we'd all have to have access to whatever IDE the chip maker has. I think an FPGA would be super cool, especially if you can just put a uC core in it, and still have some awesome peripherals that we can design. I think if you built in enough flexibility in the hardware, it should not be obsoleted for a really long time!. I know Marko wants to do such a project too. Maybe time to start defining some requirements/feature set?
By the way, ive had zero problems with both the Xmega and CPLD on this project, despite being 3.3V powered things (i think the CPLD might have a 1.8V core inside too). I remember years ago being afraid of having such hardware in the gate drive loop of a tesla coil, but it looks like it works fine.
Steve Ward, Tue Jun 19 2012, 08:34PM
I can see where Dr Spark is coming from, there is nothing quite like shooting a real gun.
Anyway, here's some design files (ehhh, minus the PCB layouts for now):
How big is your transformer? Something capable of handling 120A peak must be quite bulky (though the 400 KHz operation helps handle that I suppose).
The cores are about 2.5"x2.5"x1.25". They are in fact a lot bigger than they need to be, since i had plenty of room to fit the wire on the core with lots of space left. I mainly used these because i didnt have enough of anything smaller. The output (120A side) is wound with 10awg, and the input (60A) is wound with 12awg. With my low duty cycles, they do not warm up at all. For a real, mains powered thing, you'd probably have to use bigger copper, preferably some litz wire i think.
I also have a long-term project to make an all-digital Tesla coil controller on a FPGA (and a fiber optic multiplexed data format to go with it) and am looking for collaborators.
I guess for such a project to work out, we'd all have to have access to whatever IDE the chip maker has. I think an FPGA would be super cool, especially if you can just put a uC core in it, and still have some awesome peripherals that we can design. I think if you built in enough flexibility in the hardware, it should not be obsoleted for a really long time!
. I know Marko wants to do such a project too. Maybe time to start defining some requirements/feature set?By the way, ive had zero problems with both the Xmega and CPLD on this project, despite being 3.3V powered things (i think the CPLD might have a 1.8V core inside too). I remember years ago being afraid of having such hardware in the gate drive loop of a tesla coil, but it looks like it works fine.
Re: ArcAttack! Tesla Gun
joshua_, Tue Jun 19 2012, 10:48PM
I, too, have considered having an all digital FPGA-based controller. I've been going through a fair bit of pain with my most recent CD4046/74HCT4046-based coil (PC2 is very noise sensitive, and hence loses its mind when I take a ground strike; PC1 has an obnoxious phase shift, making it more or less unusable), and I've considered a few times using an FPGA instead of the '4046 to get more precise control. (I need to post a thread about my most recent coil; I think I first need to get some scope shots so that I can get ideas from others as to where I'm stuck.)
I also considered using just a CPLD as a tiny PLL; I think it would have just enough logic to do the job. Certainly an FPGA would be much more interesting, though; you would be able to integrate a micro, for instance, to do interrupter control.
So, if you're interested, Steves, let me know! I'm certainly on the IRC all the time...
edit: oh, and I failed to mention -- spectacular work, as always, SteveW! Very very neat packaging on it, and pushing the envelope as always. Bravo.
edit 2: I feel compelled to post:
You have some dressing up to do, Steve!
joshua_, Tue Jun 19 2012, 10:48PM
I, too, have considered having an all digital FPGA-based controller. I've been going through a fair bit of pain with my most recent CD4046/74HCT4046-based coil (PC2 is very noise sensitive, and hence loses its mind when I take a ground strike; PC1 has an obnoxious phase shift, making it more or less unusable), and I've considered a few times using an FPGA instead of the '4046 to get more precise control. (I need to post a thread about my most recent coil; I think I first need to get some scope shots so that I can get ideas from others as to where I'm stuck.)
I also considered using just a CPLD as a tiny PLL; I think it would have just enough logic to do the job. Certainly an FPGA would be much more interesting, though; you would be able to integrate a micro, for instance, to do interrupter control.
So, if you're interested, Steves, let me know! I'm certainly on the IRC all the time...
edit: oh, and I failed to mention -- spectacular work, as always, SteveW! Very very neat packaging on it, and pushing the envelope as always. Bravo.
edit 2: I feel compelled to post:
You have some dressing up to do, Steve!
Re: ArcAttack! Tesla Gun
brandon3055, Wed Jun 20 2012, 03:27AM
Nice work Steve I have a question about the transformer you used to connect the bridgees to the primary (i didn't know that was possible) using that method would it be possible to build a high voltage bridge say 300-400vdc at lower than normal current then use a transformer to lower the voltage to maby 100-200vdc at a much higher current this might make it possible to use lower power mosfets or igbt's in a high power coil what do you think?
brandon3055, Wed Jun 20 2012, 03:27AM
Nice work Steve I have a question about the transformer you used to connect the bridgees to the primary (i didn't know that was possible) using that method would it be possible to build a high voltage bridge say 300-400vdc at lower than normal current then use a transformer to lower the voltage to maby 100-200vdc at a much higher current this might make it possible to use lower power mosfets or igbt's in a high power coil what do you think?
Re: ArcAttack! Tesla Gun
Dr Hankenstein, Wed Jun 20 2012, 04:24AM
Jay Leno had a Tesla "Ray Gun" on his show about five years ago. The thing was for sale on ebay. He was comparing "wouldn't you rather have one of these" than some other mediocre item that was going for more money. The ray gun was a tesla coil much in the style of Steve's; hand held, with a neon sign xfmr mounted on top. Very cool looking, indeed! Maybe someone else also saw this episode as well? Anyway, good job on the ray gun, Steve.
hank
Dr Hankenstein, Wed Jun 20 2012, 04:24AM
Jay Leno had a Tesla "Ray Gun" on his show about five years ago. The thing was for sale on ebay. He was comparing "wouldn't you rather have one of these" than some other mediocre item that was going for more money. The ray gun was a tesla coil much in the style of Steve's; hand held, with a neon sign xfmr mounted on top. Very cool looking, indeed! Maybe someone else also saw this episode as well? Anyway, good job on the ray gun, Steve.
hank
Re: ArcAttack! Tesla Gun
Dr Hankenstein, Wed Jun 20 2012, 04:34AM
FYI: this is a newer solid state version of the ray gun @
Cheerio!
Dr Hankenstein, Wed Jun 20 2012, 04:34AM
FYI: this is a newer solid state version of the ray gun @
Cheerio!
Re: ArcAttack! Tesla Gun
Patrick, Wed Jun 20 2012, 05:38AM
Patrick, Wed Jun 20 2012, 05:38AM
Dr. Spark wrote ...
Zombies can only be killed by certified ammo @
and the brain has to be blown away to take them down. Zombies are not affected by sparks. Zombie season is almost here (Dec 21) please ensure you are prepared!
Ammo is going fast, had to go to three LGS to get all required ammo!
Prepare for the worst and hope for the best indeed.
well not to ThreadJack here, but id be hard pressed to see how 223's can be "zombie" killers, my personal chooice for an anti-zombie weapon would be the AA12 combat shotgun... and those explosive flak rounds i like so much...Steve Conner wrote ...
That's awesome! I bet the capacitors inside the secondary coil are really to hit the zombies harder.
That's awesome!
I bet the capacitors inside the secondary coil are really to hit the zombies harder.Zombies can only be killed by certified ammo @
and the brain has to be blown away to take them down. Zombies are not affected by sparks. Zombie season is almost here (Dec 21) please ensure you are prepared!
Ammo is going fast, had to go to three LGS to get all required ammo!
Prepare for the worst and hope for the best indeed.
Re: ArcAttack! Tesla Gun
Steve Ward, Wed Jun 20 2012, 05:45AM
Yes, you could do that, but it would be most efficient to simply design the tesla primary circuit to match with your transistors, so you wouldnt have to use a transformer to match it. Unless you are referring to what was previously discussed, combining the outputs of many smaller bridges to drive 1 tesla coil, which is why i use the transformers here. Im considering using the technique on some gigantic tesla coils because of limited options for capacitor configurations, this way i can better impedance match my bridge with the primary setup.
That thing is pretty sweet too. Its sad Jeff is no longer with us, he did some pretty neat stuff.
Steve Ward, Wed Jun 20 2012, 05:45AM
Nice work Steve I have a question about the transformer you used to connect the bridgees to the primary (i didn't know that was possible) using that method would it be possible to build a high voltage bridge say 300-400vdc at lower than normal current then use a transformer to lower the voltage to maby 100-200vdc at a much higher current this might make it possible to use lower power mosfets or igbt's in a high power coil what do you think?
Yes, you could do that, but it would be most efficient to simply design the tesla primary circuit to match with your transistors, so you wouldnt have to use a transformer to match it. Unless you are referring to what was previously discussed, combining the outputs of many smaller bridges to drive 1 tesla coil, which is why i use the transformers here. Im considering using the technique on some gigantic tesla coils because of limited options for capacitor configurations, this way i can better impedance match my bridge with the primary setup.
FYI: this is a newer solid state version of the ray gun @
That thing is pretty sweet too. Its sad Jeff is no longer with us, he did some pretty neat stuff.
Re: ArcAttack! Tesla Gun
Marko, Wed Jun 20 2012, 06:30AM
Hey guys - so when do we bring in some laser induced plasma channels into this?
Marko
Marko, Wed Jun 20 2012, 06:30AM
Hey guys - so when do we bring in some laser induced plasma channels into this?
Marko
Re: ArcAttack! Tesla Gun
Dr. Brownout, Wed Jun 20 2012, 01:33PM
Why is Jeff no longer with us?
Dr. Brownout, Wed Jun 20 2012, 01:33PM
Why is Jeff no longer with us?
Re: ArcAttack! Tesla Gun
Dr. Drone, Wed Jun 20 2012, 03:24PM
Dr. Drone, Wed Jun 20 2012, 03:24PM
Re: ArcAttack! Tesla Gun
Pinkamena, Wed Jun 20 2012, 07:03PM
This is awesome. I have no idea what your wrote in your post, but I can nevertheless enjoy the amazingness of that teslacoil!
Pinkamena, Wed Jun 20 2012, 07:03PM
This is awesome. I have no idea what your wrote in your post, but I can nevertheless enjoy the amazingness of that teslacoil!
Re: ArcAttack! Tesla Gun
Tetris, Thu Jun 21 2012, 03:30AM
Geeks with geek ladies are better. Geeks with high voltage ladygeeks are even more lucky! :P hehe. But there aren't a few million of them like the gun number. Knock off six zeroes! lol,
@ thread: Are you arcing to that guy? also, 1A through your arm! O_O wow even with my little knowledge on how coils work and electricity and all, that CAN'T be safe! Be careful! Now all I wonder if that can be applied to hat-coils, like "IdRatherBeCubing" did on youtube. That handheld coil is so badass. hehe!
Tetris, Thu Jun 21 2012, 03:30AM
Dr. Spark wrote ...
….must have both indeed @
So for pure Geekness, Geeks with ladies are better than Geeks with no ladies. Just saying @ !
Steve Conner wrote ...
Sorry, regular guns might be more effective at killing things, but for sheer geek points, Steve's Tesla gun is untouchable.
Hmmmm strange as all the Geek's that come to my house and the W.W.T. want to see Class three weapons ready for Zombies and really do not care about coils. Now that females are going crazy with guns, guess if you want to be a Geek and get ladies (15 million US women pack heat @ Sorry, regular guns might be more effective at killing things, but for sheer geek points, Steve's Tesla gun is untouchable.
….must have both indeed @ So for pure Geekness, Geeks with ladies are better than Geeks with no ladies. Just saying @
!Geeks with geek ladies are better. Geeks with high voltage ladygeeks are even more lucky! :P hehe. But there aren't a few million of them like the gun number. Knock off six zeroes! lol,
@ thread: Are you arcing to that guy? also, 1A through your arm! O_O wow even with my little knowledge on how coils work and electricity and all, that CAN'T be safe! Be careful! Now all I wonder if that can be applied to hat-coils, like "IdRatherBeCubing" did on youtube. That handheld coil is so badass. hehe!
Re: ArcAttack! Tesla Gun
Sulaiman, Thu Jun 21 2012, 10:28PM
I admire the amount of development leading to this project,
and really like this result,
I put the photo shooting into the air (IMG_5605) as wallpaper at work,
,,,,"what use is it?" ......D'oh.
I like it though.
P.S. most recognised it as a 'proton-pack'
Sulaiman, Thu Jun 21 2012, 10:28PM
I admire the amount of development leading to this project,
and really like this result,
I put the photo shooting into the air (IMG_5605) as wallpaper at work,
,,,,"what use is it?" ......D'oh.
I like it though.
P.S. most recognised it as a 'proton-pack'
Re: ArcAttack! Tesla Gun
Gregory, Fri Jun 22 2012, 12:24AM
How many nF are you using at primary mmc? I'm making some spice simulations here, and a phase shifted bridge really appear to do a good job!
I will try do make some circuit more simple to control it, I post here when I get some results.
Gregory, Fri Jun 22 2012, 12:24AM
How many nF are you using at primary mmc? I'm making some spice simulations here, and a phase shifted bridge really appear to do a good job!
I will try do make some circuit more simple to control it, I post here when I get some results.
Re: ArcAttack! Tesla Gun
Intra, Sun Jun 24 2012, 10:05PM
Yeah!! Of course anyone else have a serious interest in QCW coiling!!
I saw in gate_driver.pdf a HFBR-2412T. Does it mean this phase shifted topology can be midi or audio interruptible?
I have an interest in phase shifted audio/midi interruptible topology of QCW coil, because my main interest in all this - it is sound. Singing Tesla Coil in diffirent notes make different sound. In mid freq DRSSTC create something around distortion clicks, but in hi freq it create melodiousness gradient! It is incredible! ^___^ So many different sounds in one instrument!
I'm making steps in record DR's sound on Ñondenser microphone with dynamic compressor and vacuum tube preamplifier and I am very pleased with the results. Here take a place my first song on DRSSTCs
(video sequence I picked up a very ugly)
But DRSSTC can't play bass frequences and it's so sorrowfully. I have long puzzled over the bass section, until I saw your bass test
And now, when not need to buy expensive CM600 in Class D Amp, possible to make a "non-expensive" bass-coils for playing on it via bass guitar! Yahoo!! ^____^
Can you write a tutorial for it or something, with formulas of calculations and main points. Or just write some more descriptions. I want to build a Bass-QCW and use it in my sound research and I need help.
Intra, Sun Jun 24 2012, 10:05PM
Steve Ward wrote ...
Does anyone else on this forum have a serious interest in building a QCW coil?
Does anyone else on this forum have a serious interest in building a QCW coil?
Yeah!! Of course anyone else have a serious interest in QCW coiling!!
I saw in gate_driver.pdf a HFBR-2412T. Does it mean this phase shifted topology can be midi or audio interruptible?
I have an interest in phase shifted audio/midi interruptible topology of QCW coil, because my main interest in all this - it is sound. Singing Tesla Coil in diffirent notes make different sound. In mid freq DRSSTC create something around distortion clicks, but in hi freq it create melodiousness gradient! It is incredible! ^___^ So many different sounds in one instrument!
I'm making steps in record DR's sound on Ñondenser microphone with dynamic compressor and vacuum tube preamplifier and I am very pleased with the results. Here take a place my first song on DRSSTCs
(video sequence I picked up a very ugly)
But DRSSTC can't play bass frequences and it's so sorrowfully. I have long puzzled over the bass section, until I saw your bass test
And now, when not need to buy expensive CM600 in Class D Amp, possible to make a "non-expensive" bass-coils for playing on it via bass guitar! Yahoo!! ^____^
Can you write a tutorial for it or something, with formulas of calculations and main points. Or just write some more descriptions. I want to build a Bass-QCW and use it in my sound research and I need help.
Re: ArcAttack! Tesla Gun
Wolfram, Mon Jun 25 2012, 12:27PM
Does the lower Z of the secondary compared to your earlier QCWs loosen the requirements for the primary side MMC? What is the capacitance of the primary MMC?
With the use of transformers between the bridge and the tank circuit, we have the freedom to make the bridge see a different primary impedance. Can this be utilized to make the coil work with a cheaper primary MMC?
Wolfram, Mon Jun 25 2012, 12:27PM
Does the lower Z of the secondary compared to your earlier QCWs loosen the requirements for the primary side MMC? What is the capacitance of the primary MMC?
With the use of transformers between the bridge and the tank circuit, we have the freedom to make the bridge see a different primary impedance. Can this be utilized to make the coil work with a cheaper primary MMC?
Re: ArcAttack! Tesla Gun
Dr. ISOTOP, Mon Jun 25 2012, 06:50PM
QCW's have lots of RMS primary current. so the "MMC" needs to handle significant average power. Eric Goodchild uses a mica cap, I believe.
Dr. ISOTOP, Mon Jun 25 2012, 06:50PM
Wolfram wrote ...
Does the lower Z of the secondary compared to your earlier QCWs loosen the requirements for the primary side MMC? What is the capacitance of the primary MMC?
With the use of transformers between the bridge and the tank circuit, we have the freedom to make the bridge see a different primary impedance. Can this be utilized to make the coil work with a cheaper primary MMC?
Does the lower Z of the secondary compared to your earlier QCWs loosen the requirements for the primary side MMC? What is the capacitance of the primary MMC?
With the use of transformers between the bridge and the tank circuit, we have the freedom to make the bridge see a different primary impedance. Can this be utilized to make the coil work with a cheaper primary MMC?
QCW's have lots of RMS primary current. so the "MMC" needs to handle significant average power. Eric Goodchild uses a mica cap, I believe.
Re: ArcAttack! Tesla Gun
teravolt, Mon Jun 25 2012, 06:52PM
Hi Steve nice to see you got your tesla that you were talking about at the maker fair. do you think that the life time of your lithium batteries will be shortened by the type of load that your presenting to them. I did dome reading and the harder you push them the shorter the life. If you push a smaller battery the life will be short indeed but it may be more cost effective to by a larger battery because you would get more charges out of them because they will handle the load better. Do you have a battery monitor to keep it from going under the critical voltage? What do you think of the LiFePo4 batteries?
I also noticed that your using poly caps for the resonant cap how do they hold out at those frequencies?
teravolt, Mon Jun 25 2012, 06:52PM
Hi Steve nice to see you got your tesla that you were talking about at the maker fair. do you think that the life time of your lithium batteries will be shortened by the type of load that your presenting to them. I did dome reading and the harder you push them the shorter the life. If you push a smaller battery the life will be short indeed but it may be more cost effective to by a larger battery because you would get more charges out of them because they will handle the load better. Do you have a battery monitor to keep it from going under the critical voltage? What do you think of the LiFePo4 batteries?
I also noticed that your using poly caps for the resonant cap how do they hold out at those frequencies?
Re: ArcAttack! Tesla Gun
lightlinked, Tue Jun 26 2012, 03:19AM
is this, this on hack a day?
is the schematic on their t shirt your universal driver?
lightlinked, Tue Jun 26 2012, 03:19AM
is this, this on hack a day?
is the schematic on their t shirt your universal driver?
Re: ArcAttack! Tesla Gun
Wolfram, Tue Jun 26 2012, 06:16AM
I know this, I was asking if the lower secondary impedance means that the primary MMC sees less reactive power for a given sparklength.
Wolfram, Tue Jun 26 2012, 06:16AM
bwang wrote ...
QCW's have lots of RMS primary current. so the "MMC" needs to handle significant average power. Eric Goodchild uses a mica cap, I believe.
Wolfram wrote ...
Does the lower Z of the secondary compared to your earlier QCWs loosen the requirements for the primary side MMC? What is the capacitance of the primary MMC?
With the use of transformers between the bridge and the tank circuit, we have the freedom to make the bridge see a different primary impedance. Can this be utilized to make the coil work with a cheaper primary MMC?
Does the lower Z of the secondary compared to your earlier QCWs loosen the requirements for the primary side MMC? What is the capacitance of the primary MMC?
With the use of transformers between the bridge and the tank circuit, we have the freedom to make the bridge see a different primary impedance. Can this be utilized to make the coil work with a cheaper primary MMC?
QCW's have lots of RMS primary current. so the "MMC" needs to handle significant average power. Eric Goodchild uses a mica cap, I believe.
I know this, I was asking if the lower secondary impedance means that the primary MMC sees less reactive power for a given sparklength.
Re: ArcAttack! Tesla Gun
Steve Ward, Tue Jun 26 2012, 07:03PM
I'll get to some other questions soon. The MMC is 18.75nF (150nF 2kV CDE 942C caps, 8 series). It was only intended to work with the low duty cycle that the gun presents. I intend on making a better MMC with a bunch of smaller MKP caps so the heat is easier to remove from them.
As far as i know, raising the secondary Q should lower the energy storage requirement in the primary coil. I uhh, havent formally proved this in anyway other than it works a lot better with the added secondary capacitance (while keeping F_op constant, so less Lsec).
As for LiPo life, im not really too up to speed on all the details of how they handle high discharge use, but the battery is *rated* for 25C continuous and 40C burst i believe. I operate at a modest 6C discharge rate, so im pretty sure its not an issue. LiFePO4s would surely work great too.
Hooray! yes give it a try... sometimes i miss pretty obvious ways of simplifying things the first time through, and i havent tried to think of another way to make this work yet.
And someone asked about there being a fiber optic input to the gate drive control, yes you can interface it to whatever you want (just gotta write the code!). For gun use, i opted to just use real wires for my UART comm's to the gun controller.
Oh, and it was great to meet Hack A Day, i forgot to mention that it was their CPLD tutorial that really helped get this project off the ground!
Steve Ward, Tue Jun 26 2012, 07:03PM
I'll get to some other questions soon. The MMC is 18.75nF (150nF 2kV CDE 942C caps, 8 series). It was only intended to work with the low duty cycle that the gun presents. I intend on making a better MMC with a bunch of smaller MKP caps so the heat is easier to remove from them.
As far as i know, raising the secondary Q should lower the energy storage requirement in the primary coil. I uhh, havent formally proved this in anyway other than it works a lot better with the added secondary capacitance (while keeping F_op constant, so less Lsec).
As for LiPo life, im not really too up to speed on all the details of how they handle high discharge use, but the battery is *rated* for 25C continuous and 40C burst i believe. I operate at a modest 6C discharge rate, so im pretty sure its not an issue. LiFePO4s would surely work great too.
I will try do make some circuit more simple to control it, I post here when I get some results.
Hooray! yes give it a try... sometimes i miss pretty obvious ways of simplifying things the first time through, and i havent tried to think of another way to make this work yet.
And someone asked about there being a fiber optic input to the gate drive control, yes you can interface it to whatever you want (just gotta write the code!). For gun use, i opted to just use real wires for my UART comm's to the gun controller.
Oh, and it was great to meet Hack A Day, i forgot to mention that it was their CPLD tutorial that really helped get this project off the ground!
Re: ArcAttack! Tesla Gun
Intra, Wed Jun 27 2012, 08:48AM
Intra, Wed Jun 27 2012, 08:48AM
Steve Ward wrote ...
And someone asked about there being a fiber optic input to the gate drive control, yes you can interface it to whatever you want (just gotta write the code!).
I mean, can your ATmega88 midi Interrupter interface that phase shifted qcw gate driver? Or, what non-software thing need to change? Which pulse width need for this gate driver? And gate driver's MCu is already have a part of code doing recieve from fiber optic interface or it have only gun controller part?And someone asked about there being a fiber optic input to the gate drive control, yes you can interface it to whatever you want (just gotta write the code!).
Re: ArcAttack! Tesla Gun
Intra, Thu Jun 28 2012, 11:04PM
I mean, some guys like me, perhaps need more structural guide, like that, for example
Guide of that kind is real helpful, because in front of you in one place, the main points, oscilloscope screenshots and etc.
When I start building my first drsstc, I know nothing about all it and this material was a very helpful for me and for many other people, I think. Why not be able to make same guide for phase-shifted QCW? It's a needful thing now.
Intra, Thu Jun 28 2012, 11:04PM
I mean, some guys like me, perhaps need more structural guide, like that, for example
Guide of that kind is real helpful, because in front of you in one place, the main points, oscilloscope screenshots and etc.
When I start building my first drsstc, I know nothing about all it and this material
was a very helpful for me and for many other people, I think. Why not be able to make same guide for phase-shifted QCW? It's a needful thing now.Re: ArcAttack! Tesla Gun
Uspring, Tue Jul 10 2012, 05:11PM
Wolfram wrote:
Uspring, Tue Jul 10 2012, 05:11PM
Wolfram wrote:
I know this, I was asking if the lower secondary impedance means that the primary MMC sees less reactive power for a given sparklength.Yes, under some conditions which I believe hold true for Steve's design. The derivation is a bit involved so I don't think it is appropriate to this particular forum.
Re: ArcAttack! Tesla Gun
Goodchild, Fri Jul 13 2012, 10:13PM
Great Project indeed!
I've also been fiddling with the phase shifted bridge idea for a while now. Steve you mention you hard switched at turn off on one side of the bridge. What I have been doing to avoid this is to ZVS on turn off by using the devices self capacitance and also a small amount of external capacitance to commutate the tank current while the switch turns off (typically < 100nF). A small amount of delay also has to be added before the other switch is allowed to turn on. This yields near perfect ZVS at turn on an off. Another nice perk of this type of drive is the ability to control the rise and fall time out to 100nS or 200ns making the whole inverter much less noisy.
My method doesn't use a CPLD of MCU of any kind just basic logic and RC delays for the ZVS timing, also use an Opamp and comparator to generate the phase delay based on a mod voltage. But I like the idea of using a PWM ramp seems easier.
Also love the idea of using the transformers to both match and current share very sneaky!
All the best,
Eric
EDIT:
After reading more of this thread it seems you already do exactly this! I find that it's easy to make even the slower IGBT turn off with ZVS if the correct sized cap is placed in parallel with with device. So that the commutation is extended out as long as desired.
I guess what through me at first is that you said "hard Switching" even though your kinda not hard switching :P hehe
Goodchild, Fri Jul 13 2012, 10:13PM
Great Project indeed!
I've also been fiddling with the phase shifted bridge idea for a while now. Steve you mention you hard switched at turn off on one side of the bridge. What I have been doing to avoid this is to ZVS on turn off by using the devices self capacitance and also a small amount of external capacitance to commutate the tank current while the switch turns off (typically < 100nF). A small amount of delay also has to be added before the other switch is allowed to turn on. This yields near perfect ZVS at turn on an off. Another nice perk of this type of drive is the ability to control the rise and fall time out to 100nS or 200ns making the whole inverter much less noisy.
My method doesn't use a CPLD of MCU of any kind just basic logic and RC delays for the ZVS timing, also use an Opamp and comparator to generate the phase delay based on a mod voltage. But I like the idea of using a PWM ramp seems easier.
Also love the idea of using the transformers to both match and current share very sneaky!
All the best,
Eric
EDIT:
After reading more of this thread it seems you already do exactly this! I find that it's easy to make even the slower IGBT turn off with ZVS if the correct sized cap is placed in parallel with with device. So that the commutation is extended out as long as desired.
I guess what through me at first is that you said "hard Switching" even though your kinda not hard switching :P hehe
Re: ArcAttack! Tesla Gun
Steve Ward, Sun Jul 15 2012, 04:01AM
Yes, thats right Eric. I experimented with adding snubber capacitors to the IGBTs to extend ZVS at turn off, but i got the cleanest results without any capacitance added there. The devices i used have very low switch off loss (really fast), so i decided to just leave it "hard switched". And as you say, the capacitors limit the maximum phase shift since you want the load current to charge them, and not the IGBTs.
Steve Ward, Sun Jul 15 2012, 04:01AM
Yes, thats right Eric. I experimented with adding snubber capacitors to the IGBTs to extend ZVS at turn off, but i got the cleanest results without any capacitance added there. The devices i used have very low switch off loss (really fast), so i decided to just leave it "hard switched". And as you say, the capacitors limit the maximum phase shift since you want the load current to charge them, and not the IGBTs.
Re: ArcAttack! Tesla Gun
Goodchild, Sun Jul 15 2012, 07:27AM
Yeah that's kinda a down side to the phase shift as your limited to under full voltage out, but I guess at full 180 phase this shouldn't be a problem anyway because at that point it should be ZCS anyway. Although there would still be a small window in which turn off losses would be rather high.
So you say that because your switches have good turn off characteristics you just let them hard switch all the time at turn off with no ZVS? I'm curious to the problems you encountered with the capacitor snubbers in place? Did losses get higher? Or did distortion just increase?
Eric
Goodchild, Sun Jul 15 2012, 07:27AM
Steve Ward wrote ...
Yes, thats right Eric. I experimented with adding snubber capacitors to the IGBTs to extend ZVS at turn off, but i got the cleanest results without any capacitance added there. The devices i used have very low switch off loss (really fast), so i decided to just leave it "hard switched". And as you say, the capacitors limit the maximum phase shift since you want the load current to charge them, and not the IGBTs.
Yes, thats right Eric. I experimented with adding snubber capacitors to the IGBTs to extend ZVS at turn off, but i got the cleanest results without any capacitance added there. The devices i used have very low switch off loss (really fast), so i decided to just leave it "hard switched". And as you say, the capacitors limit the maximum phase shift since you want the load current to charge them, and not the IGBTs.
Yeah that's kinda a down side to the phase shift as your limited to under full voltage out, but I guess at full 180 phase this shouldn't be a problem anyway because at that point it should be ZCS anyway. Although there would still be a small window in which turn off losses would be rather high.
So you say that because your switches have good turn off characteristics you just let them hard switch all the time at turn off with no ZVS? I'm curious to the problems you encountered with the capacitor snubbers in place? Did losses get higher? Or did distortion just increase?
Eric
Re: ArcAttack! Tesla Gun
PhilGood, Sun Jul 29 2012, 06:52PM
Really interesting Project and amazing results so far, congrats Steve !
I really like the idea of adding secondary capacitors ! What kind of capacitors did you use and how did you mount them to prevent arcing inside secondary ? Why so many high value caps instead of a few HV ones ? Any close pic of the capacitors assembly inside the secondary ?
I would like to apply this concept to my 572B VTTC and see if it improves output
PhilGood, Sun Jul 29 2012, 06:52PM
Really interesting Project and amazing results so far, congrats Steve !
I really like the idea of adding secondary capacitors ! What kind of capacitors did you use and how did you mount them to prevent arcing inside secondary ? Why so many high value caps instead of a few HV ones ? Any close pic of the capacitors assembly inside the secondary ?
I would like to apply this concept to my 572B VTTC and see if it improves output
Re: ArcAttack! Tesla Gun
Steve Ward, Mon Jul 30 2012, 04:26AM
The capacitors for the secondary were B32672L8122J.
I was originally looking for some ceramic doorknob caps that would suit the job, but couldnt find anything reasonable. The long string of PP film caps seems like a real winner.
I simply soldered them face to face (sort of in a spiral pattern, 2 caps per "turn"). I was then able to fit this string of caps snugly into a PVC pipe that was about 1.4" ID (going from memory here). I think its important that the capacitor string be physically the same length as the secondary coil so that the voltage gradient along the cap string is very much the same as the gradient along the coil. This provides low field stresses inside of the coil, and keeps the capacitor string free from pesky breakouts that would destroy the thing (obviously, if it can make a 4 foot spark).
These are the only pictures i have of the MMC:
Hopefully thats enough info for you to recreate it for your VTTC. Im not sure if a coil will benefit from the added capacitance unless its streamer capacitance starts to exceed the self-capacitance of the coil. But, i think its a worthy experiment still!
Steve Ward, Mon Jul 30 2012, 04:26AM
The capacitors for the secondary were B32672L8122J.
I was originally looking for some ceramic doorknob caps that would suit the job, but couldnt find anything reasonable. The long string of PP film caps seems like a real winner.
I simply soldered them face to face (sort of in a spiral pattern, 2 caps per "turn"). I was then able to fit this string of caps snugly into a PVC pipe that was about 1.4" ID (going from memory here). I think its important that the capacitor string be physically the same length as the secondary coil so that the voltage gradient along the cap string is very much the same as the gradient along the coil. This provides low field stresses inside of the coil, and keeps the capacitor string free from pesky breakouts that would destroy the thing (obviously, if it can make a 4 foot spark).
These are the only pictures i have of the MMC:
Hopefully thats enough info for you to recreate it for your VTTC. Im not sure if a coil will benefit from the added capacitance unless its streamer capacitance starts to exceed the self-capacitance of the coil. But, i think its a worthy experiment still!
Re: ArcAttack! Tesla Gun
PhilGood, Mon Jul 30 2012, 12:46PM
Thanks Steve for the detailed explanation and pics.
What are your secondary self-capacitance without the MMC, and your topload capacitance ? (to give me an idea of the secondary MMC value I should start with).
My VTTC secondary self-capacitance is 2.3pF, my topload is 5.3pF.
I'm thinking to use a string of these small K15Y-1 caps. Their Ø is around 15mm, which is fine, and their axial outputs are perfect for series connection.
Not sure I'll get any benefit from this, but definitely worth trying it !
PhilGood, Mon Jul 30 2012, 12:46PM
Thanks Steve for the detailed explanation and pics.
What are your secondary self-capacitance without the MMC, and your topload capacitance ? (to give me an idea of the secondary MMC value I should start with).
My VTTC secondary self-capacitance is 2.3pF, my topload is 5.3pF.
I'm thinking to use a string of these small K15Y-1 caps. Their Ø is around 15mm, which is fine, and their axial outputs are perfect for series connection.
Not sure I'll get any benefit from this, but definitely worth trying it !
Re: ArcAttack! Tesla Gun
radhoo, Mon Jul 30 2012, 02:15PM
Great project, and love the quality pics!
What would be the next steps for improving the streamers even further?
radhoo, Mon Jul 30 2012, 02:15PM
Great project, and love the quality pics!
What would be the next steps for improving the streamers even further?
Re: ArcAttack! Tesla Gun
Dr. Brownout, Tue Jul 31 2012, 01:16AM
What size doorknob caps do you need? I have some here I could contribute to your experiments. I have some 30KV and 50KV caps. I dont mind contributing you have contributed a lot so I could certainly hook ya up with either 2700pF or 1700pF, 30KV and 50KV respectively.
Dr. Brownout, Tue Jul 31 2012, 01:16AM
Steve Ward wrote ...
The capacitors for the secondary were B32672L8122J.
I was originally looking for some ceramic doorknob caps that would suit the job, but couldnt find anything reasonable. The long string of PP film caps seems like a real winner.
I simply soldered them face to face (sort of in a spiral pattern, 2 caps per "turn"). I was then able to fit this string of caps snugly into a PVC pipe that was about 1.4" ID (going from memory here). I think its important that the capacitor string be physically the same length as the secondary coil so that the voltage gradient along the cap string is very much the same as the gradient along the coil. This provides low field stresses inside of the coil, and keeps the capacitor string free from pesky breakouts that would destroy the thing (obviously, if it can make a 4 foot spark).
These are the only pictures i have of the MMC:
Hopefully thats enough info for you to recreate it for your VTTC. Im not sure if a coil will benefit from the added capacitance unless its streamer capacitance starts to exceed the self-capacitance of the coil. But, i think its a worthy experiment still!
The capacitors for the secondary were B32672L8122J.
I was originally looking for some ceramic doorknob caps that would suit the job, but couldnt find anything reasonable. The long string of PP film caps seems like a real winner.
I simply soldered them face to face (sort of in a spiral pattern, 2 caps per "turn"). I was then able to fit this string of caps snugly into a PVC pipe that was about 1.4" ID (going from memory here). I think its important that the capacitor string be physically the same length as the secondary coil so that the voltage gradient along the cap string is very much the same as the gradient along the coil. This provides low field stresses inside of the coil, and keeps the capacitor string free from pesky breakouts that would destroy the thing (obviously, if it can make a 4 foot spark).
These are the only pictures i have of the MMC:
Hopefully thats enough info for you to recreate it for your VTTC. Im not sure if a coil will benefit from the added capacitance unless its streamer capacitance starts to exceed the self-capacitance of the coil. But, i think its a worthy experiment still!
What size doorknob caps do you need? I have some here I could contribute to your experiments. I have some 30KV and 50KV caps. I dont mind contributing you have contributed a lot so I could certainly hook ya up with either 2700pF or 1700pF, 30KV and 50KV respectively.
Re: ArcAttack! Tesla Gun
Steve Ward, Mon Aug 06 2012, 04:49AM
Very generous offer! But sadly, i have a bunch of similar doorknob caps and they are simply too much capacitance. My MMC added just 17pF total.
Im not sure if i remember that. Its a 3.3"x6" winding of 28awg with a 2"x8" toroid. I want to say ~8pF for the coil and toroid together.
Steve Ward, Mon Aug 06 2012, 04:49AM
What size doorknob caps do you need? I have some here I could contribute to your experiments. I have some 30KV and 50KV caps. I dont mind contributing you have contributed a lot so I could certainly hook ya up with either 2700pF or 1700pF, 30KV and 50KV respectively.
Very generous offer! But sadly, i have a bunch of similar doorknob caps and they are simply too much capacitance. My MMC added just 17pF total.
What are your secondary self-capacitance without the MMC, and your topload capacitance ? (to give me an idea of the secondary MMC value I should start with).
Im not sure if i remember that. Its a 3.3"x6" winding of 28awg with a 2"x8" toroid. I want to say ~8pF for the coil and toroid together.
Re: ArcAttack! Tesla Gun
PhilGood, Sat Aug 11 2012, 09:03PM
Thanks Steve for the additional info So basically twice the secondary+topload capacitance seems a good value to start with.
Then I tried to measure the resonnant frequency of primary and secondary using the Grid-Dipping method
I found the primary resonant frequency to be 1.946MHz, so almost equal to the coil operation frequency.
When I mesured the secondary free resonant frequency, I found it to be above 2MHz (dunno the exact value cause my signal generator max frequency is 2MHz
)
Then I added a piece of 15cm lenght (my coil's streamer lenght) copper wire to my topload, pointing outwards, and my secondary resonnant frequency was down to the expected 1.950MHz !
So I think we can say any spark lenght will detune the coil.
And as you suggested in you first post there might be other benefits in adding capacitance to the secondary. I'm really curious about this and will try it on my VTTC as soon as I get suitable caps
PhilGood, Sat Aug 11 2012, 09:03PM
Thanks Steve for the additional info
So basically twice the secondary+topload capacitance seems a good value to start with.Steve Ward wrote ...
Hopefully thats enough info for you to recreate it for your VTTC. Im not sure if a coil will benefit from the added capacitance unless its streamer capacitance starts to exceed the self-capacitance of the coil. But, i think its a worthy experiment still!
I recently measured my VTTC resonnant frequency (during operation) at 1.948MHzHopefully thats enough info for you to recreate it for your VTTC. Im not sure if a coil will benefit from the added capacitance unless its streamer capacitance starts to exceed the self-capacitance of the coil. But, i think its a worthy experiment still!
Then I tried to measure the resonnant frequency of primary and secondary using the Grid-Dipping method
I found the primary resonant frequency to be 1.946MHz, so almost equal to the coil operation frequency.
When I mesured the secondary free resonant frequency, I found it to be above 2MHz (dunno the exact value cause my signal generator max frequency is 2MHz
)Then I added a piece of 15cm lenght (my coil's streamer lenght) copper wire to my topload, pointing outwards, and my secondary resonnant frequency was down to the expected 1.950MHz !
So I think we can say any spark lenght will detune the coil.
And as you suggested in you first post there might be other benefits in adding capacitance to the secondary. I'm really curious about this and will try it on my VTTC as soon as I get suitable caps
Re: ArcAttack! Tesla Gun
Conundrum, Tue Aug 14 2012, 05:50PM
A useful trick is to use a very fine nozzle and helium supply to make the arcs longer.
This particular method was pioneered by He-Who-Shall-Not-Be-Named but works well.
Google "Amasci" ...
Conundrum, Tue Aug 14 2012, 05:50PM
A useful trick is to use a very fine nozzle and helium supply to make the arcs longer.
This particular method was pioneered by He-Who-Shall-Not-Be-Named but works well.
Google "Amasci" ...
Re: ArcAttack! Tesla Gun
testtest, Wed Aug 15 2012, 11:53PM
interesting photo. Awesome.
1)
would a small fan blowing forced air in the center of the coil help make the sparks and discharge more straight? You probably dont want to carry an inert gas tank too.
2) hope you have not tried this with someone that has a pacemaker, or insulin metering device, or...... you get the picture!
nice work`
testtest, Wed Aug 15 2012, 11:53PM
interesting photo. Awesome.
1)
would a small fan blowing forced air in the center of the coil help make the sparks and discharge more straight? You probably dont want to carry an inert gas tank too.
2) hope you have not tried this with someone that has a pacemaker, or insulin metering device, or...... you get the picture!
nice work
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