Mini SGTC
Avalanche, Sat May 27 2006, 09:29PMThis started off as just a quick 'something to do with my flyback'.
I have become totally hooked now, and I have been playing around and improving this coil all day, and plan to build it into a proper coil eventually, so I think it deserves a thread on the project board! It's my first SGTC, after building several solid state coils. I can't believe how noisy even this small coil is, how do you guys cope with large coils
fRes = Approx 1.2Mhz
Tank Cap - 5 beer bottle caps (about 5nF?)
Primary - tapped at 6 turns
Secondary dimensions - 35mm diameter, 75mm winding length.
Topload - Foil covered table tennis ball
Anyway it all started out with a single beer bottle cap, and I noticed I was getting the most output with the maximum number of primary turns, so I simply started drinking more beer and slowly adding capacitors. I am now up to 5 caps, still tapped at the furthest turn - so I think it can do more!
Coil is running from a ZVS driven flyback, and has a 2 spark spark gap (whatever that is called!)
The setup has already been through a number of revisions, and I'm on my second ZVS circuit. See below for pic of latest setup, and a video. The post I made in the 'add your tc here' thread is already out of date...
The coil is doing about 4" to air, even though it looks less on the photos
Any suggestions on how I could improve it would be most welcome
Latest Video: 1.3MB MPEG1
Re: Mini SGTC
ragnar, Sat May 27 2006, 11:01PM
Aw, he's cute, Avalanche. I saw it last night in the "Post your TC here" thread, but no sparkies =P
I reckon you could improve it by constructing a rolled cap (for size reasons, compared to the bottle cap), lying it down next to the flyback, and bolting it all down to a nice little board. Mini SGTCs just don't have the charm unless they're portable and neatly finished (like your other coils
)
Are you losing much in the way of corona off your bottles? If so, for efficiency, perhaps you'd consider some corona rings.. =)
Wow, just saw the video - there's a lot of corona there! How does he perform with a single breakout point on the topload?
ragnar, Sat May 27 2006, 11:01PM
Aw, he's cute, Avalanche. I saw it last night in the "Post your TC here" thread, but no sparkies =P
I reckon you could improve it by constructing a rolled cap (for size reasons, compared to the bottle cap), lying it down next to the flyback, and bolting it all down to a nice little board. Mini SGTCs just don't have the charm unless they're portable and neatly finished (like your other coils
)Are you losing much in the way of corona off your bottles? If so, for efficiency, perhaps you'd consider some corona rings.. =)
Wow, just saw the video - there's a lot of corona there! How does he perform with a single breakout point on the topload?
Re: Mini SGTC
Marko, Sat May 27 2006, 11:32PM
My first TC ever was too a miniature SGTC.
It was powered by NE555 ignition coil driven from 12V (I didn't even have an adequate power supply), about 10kV, and it gave some 5cm sparks at maximum (but very hazy and barely visible).
Later I tried few times with flyback but I never got into something more than aligator clips and bunch of bottles on the table.
I hope you aren't going to build some 30nF cap this way.
Actually you don't have some special restraints in choosing tank cap since you are charging with DC.
For more bang energy you can simply set the gap more loosely so the cap charges to higher voltage.
Maybe you can later play with resonant charging, different cap types (MMC; rolled) etc.
It looks much less than that, it seems like 10cm arc would probably engulf secondary completely
For what I can tell sparks seem to be about 5-6cm long in the movies.
One thing I was dissapointed with samll SGTC's is that they seem to be quite poor EF transmitters. I could weakly light up neon bulb only by drawing an arc with it.
Resonators also didn't respond at all.
Marko, Sat May 27 2006, 11:32PM
My first TC ever was too a miniature SGTC.
It was powered by NE555 ignition coil driven from 12V (I didn't even have an adequate power supply), about 10kV, and it gave some 5cm sparks at maximum (but very hazy and barely visible).
Later I tried few times with flyback but I never got into something more than aligator clips and bunch of bottles on the table.
so I simply started drinking more beer and slowly adding
I hope you aren't going to build some 30nF cap this way.
Actually you don't have some special restraints in choosing tank cap since you are charging with DC.
For more bang energy you can simply set the gap more loosely so the cap charges to higher voltage.
Maybe you can later play with resonant charging, different cap types (MMC; rolled) etc.
The coil is doing about 4" to air, even though it looks less on the photos
It looks much less than that, it seems like 10cm arc would probably engulf secondary completely
For what I can tell sparks seem to be about 5-6cm long in the movies.
One thing I was dissapointed with samll SGTC's is that they seem to be quite poor EF transmitters. I could weakly light up neon bulb only by drawing an arc with it.
Resonators also didn't respond at all.
Re: Mini SGTC
Mike, Sun May 28 2006, 02:04AM
Awesome coil Avalanche, it is a beauty!
The primary and secondary together look great, and a cool arc picture. For a new cap may I suggest Polystyrene Plate capacitors
I have been hoping someone would test em on a SGTC, and these might just be what you need.
Well good job!
-Mike
Mike, Sun May 28 2006, 02:04AM
Awesome coil Avalanche, it is a beauty!
The primary and secondary together look great, and a cool arc picture. For a new cap may I suggest Polystyrene Plate capacitors
I have been hoping someone would test em on a SGTC, and these might just be what you need.
Well good job!
-Mike
Re: Mini SGTC
Avalanche, Sun May 28 2006, 10:54AM
Thanks for the comments
Yes good suggestions for new capacitors. I will experiment with a rolled cap and plate caps (or similar), and post my results. The setup is very lossy, if I disconnect the coil and power up the flyback, everything hisses and it stinks of corona. I guess eliminating that would help! Might try an MMC also, I have some small caps but I'm not sure on their voltage.
lol, I'm getting close. I'd better sober up before I wind the new secondary for that cap
Here's a few new pics, first up is a screw as a breakout point. The behaviour of this coil is totally different to any of my sstcs! The corona looks like it is liquid flowing off the top of the screw
The third photo is interesting, if you have a look at the full size photo you can see arcing between turns on the secondary! The voltage rise must be huge, it must take at least 1kv to do that?
Avalanche, Sun May 28 2006, 10:54AM
Thanks for the comments
wrote ...
I reckon you could improve it by constructing a rolled cap (for size reasons, compared to the bottle cap), lying it down next to the flyback, and bolting it all down to a nice little board.
I reckon you could improve it by constructing a rolled cap (for size reasons, compared to the bottle cap), lying it down next to the flyback, and bolting it all down to a nice little board.
wrote ...
For a new cap may I suggest Polystyrene Plate capacitors
For a new cap may I suggest Polystyrene Plate capacitors
Yes good suggestions for new capacitors. I will experiment with a rolled cap and plate caps (or similar), and post my results. The setup is very lossy, if I disconnect the coil and power up the flyback, everything hisses and it stinks of corona. I guess eliminating that would help! Might try an MMC also, I have some small caps but I'm not sure on their voltage.
wrote ...
I hope you aren't going to build some 30nF cap this way.
I hope you aren't going to build some 30nF cap this way.
lol, I'm getting close. I'd better sober up before I wind the new secondary for that cap
wrote ...
How does he perform with a single breakout point on the topload?
How does he perform with a single breakout point on the topload?
Here's a few new pics, first up is a screw as a breakout point. The behaviour of this coil is totally different to any of my sstcs! The corona looks like it is liquid flowing off the top of the screw
The third photo is interesting, if you have a look at the full size photo you can see arcing between turns on the secondary! The voltage rise must be huge, it must take at least 1kv to do that?
Re: Mini SGTC
Marko, Sun May 28 2006, 11:43AM
I like your streamers, especially in second pic. Mine were a lot thinner and hazy, probably because coil wasn't tuned properly.
I did also figure out that bottle caps are especially bad for low power because of corona losses.
It seems that you are already overpowering the coil since racing sparks are occuring.
You can maybe try bigger topload to prevent this.
Marko, Sun May 28 2006, 11:43AM
I like your streamers, especially in second pic. Mine were a lot thinner and hazy, probably because coil wasn't tuned properly.
I did also figure out that bottle caps are especially bad for low power because of corona losses.
It seems that you are already overpowering the coil since racing sparks are occuring.
You can maybe try bigger topload to prevent this.
Re: Mini SGTC
Self Defenestrate, Sun May 28 2006, 03:04PM
For the between turn arcing, I would suggest finding some acrylic tube to fit over the secondary, sealing it in with hot glue, and filling the space inbetween with oil. I had beaten the secondary on my 1kv coil until it had no output from arcing to itself, but the oil fixed it up and it works great now. Your topload reminds me of TDU's 18 inch coil, but without four mot's worth of power behind it.
Self Defenestrate, Sun May 28 2006, 03:04PM
For the between turn arcing, I would suggest finding some acrylic tube to fit over the secondary, sealing it in with hot glue, and filling the space inbetween with oil. I had beaten the secondary on my 1kv coil until it had no output from arcing to itself, but the oil fixed it up and it works great now. Your topload reminds me of TDU's 18 inch coil, but without four mot's worth of power behind it.
Re: Mini SGTC
Marko, Sun May 28 2006, 03:11PM
Noo
It would ruin the nice coil, and especially oil would be very messy, maybe poliester or epoxy would do if it's really necessary.
Since coil is not CW it will hardly set itself on fire or damage the top of secondary severely.
you can give it few more coats of poliurethane if you are really afraid of blowing it up.
Marko, Sun May 28 2006, 03:11PM
would suggest finding some acrylic tube to fit over the secondary, sealing it in with hot glue, and filling the space inbetween with oil.
Noo
It would ruin the nice coil, and especially oil would be very messy, maybe poliester or epoxy would do if it's really necessary.Since coil is not CW it will hardly set itself on fire or damage the top of secondary severely.
you can give it few more coats of poliurethane if you are really afraid of blowing it up.
Re: Mini SGTC
Avalanche, Sun May 28 2006, 03:47PM
Yeah it doesn't appear to be damaging the coil, so I will probably leave it for now.
I've been constructing roll up caps anyway, but I am not having much luck
The caps themselves are working really well, it's just that I don't have a clue as to their capacitance.
The one I'm using at the moment is about the size of an AA cell, and is made from 2 strips of aluminium foil, and 2 strips of overhead projector transparency. It seems to be tuned to the coil, in that altering the tapping on either way decreases output, but the output itself is anly about half an inch
I guess the coil is probably tuned to a harmonic.
At a very rough estimate, how would these caps compare to beer bottle caps in terms of capacitance? I get the feeling this cap is probably about 10nF maybe?
I made a really huge roll up cap, and the spark gap sounded like a machine gun with it connected It must have been about 100nF
Once I sort out a capacitor I will start building this coil onto a base.
Avalanche, Sun May 28 2006, 03:47PM
Yeah it doesn't appear to be damaging the coil, so I will probably leave it for now.
I've been constructing roll up caps anyway, but I am not having much luck
The caps themselves are working really well, it's just that I don't have a clue as to their capacitance.The one I'm using at the moment is about the size of an AA cell, and is made from 2 strips of aluminium foil, and 2 strips of overhead projector transparency. It seems to be tuned to the coil, in that altering the tapping on either way decreases output, but the output itself is anly about half an inch
I guess the coil is probably tuned to a harmonic. At a very rough estimate, how would these caps compare to beer bottle caps in terms of capacitance? I get the feeling this cap is probably about 10nF maybe?
I made a really huge roll up cap, and the spark gap sounded like a machine gun with it connected
It must have been about 100nF Once I sort out a capacitor I will start building this coil onto a base.
Re: Mini SGTC
Steve Ward, Sun May 28 2006, 06:23PM
If you know the thickness of the plastic, and its dielectric constant (you can look it up), then you can figure out the capacitance.
C = (K*Eo*A*N)/d
K is the dielectric constant (around 2.0 for PP/PE).
Eo is the permittivity of air = 8.85 x 10-12 F/m
A is the plate area
d is the thickness of the dielectric.
N is the number of plates - 1 (so for a rolled cap, N = 1). Or the number of dielectric "plates", if you like.
Hope that helps.
Steve Ward, Sun May 28 2006, 06:23PM
If you know the thickness of the plastic, and its dielectric constant (you can look it up), then you can figure out the capacitance.
C = (K*Eo*A*N)/d
K is the dielectric constant (around 2.0 for PP/PE).
Eo is the permittivity of air = 8.85 x 10-12 F/m
A is the plate area
d is the thickness of the dielectric.
N is the number of plates - 1 (so for a rolled cap, N = 1). Or the number of dielectric "plates", if you like.
Hope that helps.
Re: Mini SGTC
Avalanche, Mon May 29 2006, 02:37PM
Thanks, I calaculated it to be only 0.27nF, that doesn't seem right somehow. I think I need about 6nF for this coil, I will probably just make an MMC
Avalanche, Mon May 29 2006, 02:37PM
Thanks, I calaculated it to be only 0.27nF, that doesn't seem right somehow. I think I need about 6nF for this coil, I will probably just make an MMC
Re: Mini SGTC
Marko, Mon May 29 2006, 06:49PM
Homemade rolled cap is still ging to be HUGE, for 6nF you need a pretty big tube to fit it in. Look at TDU's site.
You need some nice LDPE sheets and mineral oil to make it work reliably.
But you won't get that cap easily to be in size parameters of the small secondary.
For that bottles, I have two big ones here that measure 0,7nf each, so let's say your smaller ones are 0,5 and bigger are like mine. (I guess glass thickness doesn't diffeer much).
That would be 3*0,5 + 2*0.7 = 2,9nF.
Probably the MMC would be a neat thing to do but you'l be quite limited in voltage.
You can try to find some small, highest-possible voltage caps, I think you need some pretty high voltage (30kV+) for that ZVS.
Again this is pain if biggest you have are let's say 1-2kV and you need to series a huge bunch of them.
Marko, Mon May 29 2006, 06:49PM
Homemade rolled cap is still ging to be HUGE, for 6nF you need a pretty big tube to fit it in. Look at TDU's site.
You need some nice LDPE sheets and mineral oil to make it work reliably.
But you won't get that cap easily to be in size parameters of the small secondary.
For that bottles, I have two big ones here that measure 0,7nf each, so let's say your smaller ones are 0,5 and bigger are like mine. (I guess glass thickness doesn't diffeer much).
That would be 3*0,5 + 2*0.7 = 2,9nF.
Probably the MMC would be a neat thing to do but you'l be quite limited in voltage.
You can try to find some small, highest-possible voltage caps, I think you need some pretty high voltage (30kV+) for that ZVS.
Again this is pain if biggest you have are let's say 1-2kV and you need to series a huge bunch of them.
Re: Mini SGTC
Avalanche, Mon May 29 2006, 07:05PM
30kv
I always thought that if my gap fired at, say 5kv, I wouldn't need to make a cap with a voltage rating the same as the flyback... I'll have to take that into account.
I'll probably buy a bunch of those yellow poly caps soon, I can get 10nF or 22nF caps rated 1500v each.
I've blown up a number of caps already trying to make an MMC
Avalanche, Mon May 29 2006, 07:05PM
30kv
I always thought that if my gap fired at, say 5kv, I wouldn't need to make a cap with a voltage rating the same as the flyback... I'll have to take that into account.I'll probably buy a bunch of those yellow poly caps soon, I can get 10nF or 22nF caps rated 1500v each.
I've blown up a number of caps already trying to make an MMC
Re: Mini SGTC
Marko, Mon May 29 2006, 11:06PM
You should make MMC quite a bit higher than input voltage for long and prosper life.
Theoreticaly you can use it at somewhat-higher-than sparkgap voltage, but it is enough that gap misses one firing and it will die.
You can maybe fight this with safety gap, that must be well adjusted.
And equalising resistors are apsolutely necessary.
I once easily blew my big 20kV MMC with rotary gap and 15kV transformer that way!
Coil looks good, and you could even put much bigger secondary on it
Wtth some 200W of power you could perfectly use that 40mm PVC pipe, maybe 20cm long or so.
You have much more power there that this small secondary can give off.
It seems that you have plenty of space left in that case, so you can try to make a stacked capacitor or a nice big MMC. I tought that you were about to make the box much smaller...
Marko, Mon May 29 2006, 11:06PM
You should make MMC quite a bit higher than input voltage for long and prosper life.
Theoreticaly you can use it at somewhat-higher-than sparkgap voltage, but it is enough that gap misses one firing and it will die.
You can maybe fight this with safety gap, that must be well adjusted.
And equalising resistors are apsolutely necessary.
I once easily blew my big 20kV MMC with rotary gap and 15kV transformer that way!
Coil looks good, and you could even put much bigger secondary on it
Wtth some 200W of power you could perfectly use that 40mm PVC pipe, maybe 20cm long or so.
You have much more power there that this small secondary can give off.
It seems that you have plenty of space left in that case, so you can try to make a stacked capacitor or a nice big MMC. I tought that you were about to make the box much smaller...
Re: Mini SGTC
Plasmaniac, Tue May 30 2006, 12:44PM
I've put my 3. nanoSGTC(ugly setup) in a plastic tube and filled it with wax after racing sparks and top-to-bottom streamers killed version 1 and 2. The coil is 2x4 (
) cm, the tubing 2.5x5cm big and there are still some top-to-bottom streamers if I open the gap >0.5mm (the MMC is rated for 16kV DC... kind of wasteful...). At least the streamers dont set the coil on fire anymore. 
Plasmaniac, Tue May 30 2006, 12:44PM
I've put my 3. nanoSGTC(ugly setup) in a plastic tube and filled it with wax after racing sparks and top-to-bottom streamers killed version 1 and 2. The coil is 2x4 (
) cm, the tubing 2.5x5cm big and there are still some top-to-bottom streamers if I open the gap >0.5mm (the MMC is rated for 16kV DC... kind of wasteful...). At least the streamers dont set the coil on fire anymore. Re: Mini SGTC
Avalanche, Tue May 30 2006, 04:26PM
Thanks for the comments
I've decided I'm definitely going for an MMC now, and this coil has turned into quite a large unplanned project!
As for the case, I already had the wooden supports so it was just to save time. It turned out neater than I had planned, and I even sanded down and stained the wood to try and get it all looking similar (it is built with oak, beech, and plywood). Anyway the flyback can stand upright in the case as it is, and I have room for the MMC.
I will probably leave the secondary for now, but depending on performance with the new MMC I will either wind a new secondary, or start a new coil altogether
New sparkgap is a 4-spark multigap made from brass nuts, spaced .5mm apart.
Avalanche, Tue May 30 2006, 04:26PM
Thanks for the comments
I've decided I'm definitely going for an MMC now, and this coil has turned into quite a large unplanned project!
As for the case, I already had the wooden supports so it was just to save time. It turned out neater than I had planned, and I even sanded down and stained the wood to try and get it all looking similar (it is built with oak, beech, and plywood). Anyway the flyback can stand upright in the case as it is, and I have room for the MMC.
I will probably leave the secondary for now, but depending on performance with the new MMC I will either wind a new secondary, or start a new coil altogether
New sparkgap is a 4-spark multigap made from brass nuts, spaced .5mm apart.
Re: Mini SGTC
vasil, Tue May 30 2006, 08:48PM
Turn to MMC Avalanche, you waste a lot of power with those loosy homemade caps. Experiment with the gap and the input voltage for the driver. For a specific voltage input the gap will work just fine. Apply full voltage and then crank down the variac until the BPS go low and the streamers are eratic then turn up a bit. You will see that the spark gap noise has some good tone when everything is right.
vasil, Tue May 30 2006, 08:48PM
Turn to MMC Avalanche, you waste a lot of power with those loosy homemade caps. Experiment with the gap and the input voltage for the driver. For a specific voltage input the gap will work just fine. Apply full voltage and then crank down the variac until the BPS go low and the streamers are eratic then turn up a bit. You will see that the spark gap noise has some good tone when everything is right.
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