Re: my secondary coil, is this OK?
Austin, Thu Aug 27 2009, 02:33AM

you going to coat that thing?

Re: my secondary coil, is this OK?
raff, Thu Aug 27 2009, 03:38AM

its already coated ... 3 layers plastic varnish

Re: my secondary coil, is this OK?
Mads Barnkob, Thu Aug 27 2009, 04:47PM

The bottom termination looks fine, but the top.. I would remove the screw and washer and lead the wire through a hole or slit made in the plastic cap, you risc corona/break out from the washer. You could use a large enough toroid, but just to be safe avoid sharp points at the HV end.

You secondary resonates around 640kHz, what are you planning to use it for?

Re: my secondary coil, is this OK?
raff, Thu Aug 27 2009, 10:07PM

Hi Mads

Thanks for that tip.. :)

ok looks like ill have to remove that screw/washer there. Its main purpose was to hold the top cap, but could also be used as a breakout point<sort of> ... but ill remove it anyway and place a torriod on top..

honestly, I still dont have plans what Im going to use this secondary for.. maybe a small conventional SGTC driven by a ZVS flyback driver , or an SSTC <still not sure what driver/circuit to use either> ...still reading on the hvwiki for info..

some parts are hard to come by here, and budget is a bit tight

this is my first time building a tesla coil <and im excited and SCARED as well hehe>

OT: right now im "playing" with the zvs flyback circuit (and getting GOOD results btw)

Re: my secondary coil, is this OK?
Mads Barnkob, Fri Aug 28 2009, 04:31AM

It would be fine to build a flyback driven SGTC as your first tesla coil, its simple, gives fine results and can usually be built from stuff you find.

You could just use nylon screws instead, its all about that the only conducting part on the secondary should be the wire.

Re: my secondary coil, is this OK?
raff, Fri Aug 28 2009, 06:27AM

yes I agree better start on simpler things 1st.. Im scavenging parts to use as power supply for zvs(will use the STEP-UP transformer found on UPS ,and wire them backwards as step-down) Ive got one here.. the primary measures about 8.6ohms and secondary about .9ohms.. have PLUGED it in 220VAC and I measured its output at about 13Vac.. not so sure about the ampere rating of this thing though.. maybe in the vicinity of 5-6A.. guage of winding is (I think) close to #10?

regarding SGTC, I dont know if I could get one of those NICECAPS for the primary, so I plan on making one DIY...

any site you might wish to recommend?

Re: my secondary coil, is this OK?
eniyuki, Fri Aug 28 2009, 10:07AM

hehe sir rafft welcome sa 4hv.org, grabe mga tao dito pag dating sa tesla coils,.. Hehe lalo na pag nakilala mo si Herr Zapp
Goodluck sir!

Re: my secondary coil, is this OK?
HV Enthusiast, Fri Aug 28 2009, 11:31AM

looks good although i really don't like the screws protruding into the secondary at the top of the coil. Get rid of them or at least replace them with nylon hardware.

Re: my secondary coil, is this OK?
Herr Zapp, Fri Aug 28 2009, 03:16PM

eniyuki wrote:
"hehe sir rafft welcome sa 4hv.org, grabe mga tao dito pag dating sa tesla coils,.. Hehe lalo na pag nakilala mo si Herr Zapp"

Tagalog????

Herr Zapp

Re: my secondary coil, is this OK?
raff, Fri Aug 28 2009, 10:45PM

hi Herr
yes tagalog :)


back to topic: later ill be looking for nylon screws(if I do manage to find one on hardware store) . find a suitable material for toroid(or just a sphere) and plastic materials for use as HV cap...

Re: my secondary coil, is this OK?
raff, Sat Aug 29 2009, 01:15PM

guys,

After googling/reading for some time... my first rolled HV cap :) tommorow I will test this cap with my mazzilli flyback driver // spark gap

Aluminum sheet measures 18cm x 24cm and I am using OH transparency... measured capacitance : 7.85nF

"air trapped" shown in image is NOT from the foil/transparency, but from the cellophane tape...

Re: my secondary coil, is this OK?
raff, Sat Aug 29 2009, 05:04PM

here is a mock-up of my future SGTC ..bottom right showing the home-made cap...











will test the cap tommorow..1st things first.. then search again a way to mount the toroid (w/c is still BARE) .... then make a nice pancake primary... and lastly the sparkgap (maybe ill make a multiple gap)..

Re: my secondary coil, is this OK?
raff, Sun Aug 30 2009, 02:02AM

I see a small LIGHT already

testing my home-made cap... noisy old switches (SG) haha



can't wait to finish my flybck driven SGTC

Re: my secondary coil, is this OK?
raff, Sun Aug 30 2009, 05:56AM

guys

I forgot to ask this basic question:

since Im done with the secondary coil with 640KHz resonance(thanks MADS), HOW do I compute for turns on primary coil(flat pancake) and the tank cap?

Im having trouble understanding those java calculators around the net...

EDIT: btw I will be using flyback driver for this SGTC

Re: my secondary coil, is this OK?
Mads Barnkob, Sun Aug 30 2009, 07:07AM

You really just should invest the time to understand javatc, it is an invalueable tool.

This is how I would do it. (in metric)

surroundings: 200 cm in all of them, for small and medium coils run indoor.

secondary: the dimensions, I calculate turns number/winding length with the helical coil calculator:

distance between windings are 10% of the wire diameter, in general, a 0.5 mm wire will have 0.05 mm varnish.

primary: you can start off by having it 3 cm from the secondary and then keep 1-2 cm space between windings, try to aim for 6 - 12 primary turns depending on what you can get for resonance with your capacitor.

primary lead length, should be no problem.

topload, I suggest you turn both your tins so they form a toroid like form instead of having the sharp ends down and up, have them in the middle. try to approximate its dimensions with 2 discs and a cylinder.

you can now get javatc to tune your primary circuit and adjust coupling to the one it suggests

Re: my secondary coil, is this OK?
raff, Sun Aug 30 2009, 08:26AM

Mads,

sorry but I have never seen those sites before...I guess I havent googled enough thanks for the links.. will TRY understanding it :)


EDIT:
I was about to ask you what value I should put in the "distance between windings" until I reREAD your post.. :) cool! they are VERY close to the actual measurements I have made.. THANKS again!!

EDIT2:
another thing, is there a cap calculator for the LC primary? I have only found calc for NST... will my home-made cap (7.8nF) work for this? like If I adjust "taps" on the primary?

Re: my secondary coil, is this OK?
Plasma Lover, Sun Aug 30 2009, 09:09PM


As for 'Edit2', you will need to use the properly-sized capacitor to achieve near-resonance, otherwise you will not have an efficient coil and will most likely destroy your transformer/capacitor due to voltage reversals and spikes.

Re: my secondary coil, is this OK?
Arcstarter, Sun Aug 30 2009, 09:52PM

another thing, is there a cap calculator for the LC primary? I have only found calc for NST... will my home-made cap (7.8nF) work for this? like If I adjust "taps" on the primary?

I am not sure if there is a calculator, but usually you just get the capacitor that will charge to full voltage with the most capacitance you can, without the transformer not being able to charge it fast enough. Then, you tune the primary to resonate with the capacitor at the frequency of your secondary.

That way, you can adjust the LC circuit to resonate near the secondary, yet still have a capacitor that will charge fast enough, while still having enough capacitance to get the most out of the available power.

Re: my secondary coil, is this OK?
raff, Mon Aug 31 2009, 12:20AM

hi guys
I still dont get the point(how to get resonance) until I experience it in actual hardware.yesterday while I was playing with cap&gap, adjusting distance of "gap" varied the charge-discharge cycle..hence the "freq",right?

I also plan to use air blower to cool the gap and to quench the spark.

Im still looking for a NICE topload..cant seem to find those 'ducts' locally..too bad

Re: my secondary coil, is this OK?
Coronafix, Mon Aug 31 2009, 01:03AM

I may have missed it somewhere but what are you using to drive your tank circuit? An NST? If so, then you can calculate the correct cap value quite easily.
Resonance is a function of an inductance (L) and a capacitance (C) together. It has nothing to do with the spark gap distance. You tune a coil by adjusting the primary inductance.

Re: my secondary coil, is this OK?
raff, Mon Aug 31 2009, 03:45AM

hi Coronafix

im using flyback driver(mazzilli) as input for SGTC..

this will be my 1st SGTC (or in general , a tesla coil)

how do I know if my tesla coil is IN RESONANCE?

I know for sure one of them is LONGER spark output

Re: my secondary coil, is this OK?
Coronafix, Mon Aug 31 2009, 08:17AM


In that case calculating the correct cap for that isn't so easy. I think the cap you are using will be fine.

To calculate the resonance you need to work out what the secondary frequency will be. This will be a
combination of the inductance of the secondary, its self capacitance and the capacitance of your topload.
Then plug the frequency and your chosen capacitance value into the resonance equation to work out what
inductance you need. Wind a primary with enough inductance and give it room to move because the frequency of a
coil drops slightly as it creates sparks, so adding 10% inductance to the calculated usually works better.

This is where tesla coil calculators such as JavaTC really help.

A list of the equations,

Re: my secondary coil, is this OK?
raff, Tue Sept 01 2009, 01:40AM

Coronafix,

Mads has calculated my secondary winding to be resonating at aroung 640KHz... now I have used deepfriedneon site to calculate for my primary LC.. my cap measures 7.8nF on the LCmeter... the calculator says its around 634KHz with L=9uH C7=nF .... is this my proper way of calculating/tuning it?

no problems measuring L on the primary coil once its in place because I have my LC meter in hand..

Re: my secondary coil, is this OK?
Coronafix, Tue Sept 01 2009, 03:57AM

I plug your numbers into Javatc and get 685kHz for your secondary, but once you have a topload this frequency will be lower depending on the size of it.
If you use javatc it will tell you how many turns you need, just tick the "allow javatc to tune my coil" box.

Re: my secondary coil, is this OK?
raff, Tue Sept 01 2009, 06:00AM

guys,

here is another mockup... secondary 640-685KHz reso

I will have a go at helical primary first..

primary = L 9.xxuH / C 7.8nF = 593KHz (not quite close enough) I think ill have to reDO my helical primary.. it was 8T.. will try 7.5T or 7T.... wish this primary was BARE so I could just TAP into it







as for this topload, its NOT done yet..and its HELD by a plastic screw(bolt/nut found on toilet seat covers LoL) I still have to PUT "something" in the sides so it could be like a torroid.. maybe a crumpled aluminum foil and made into a ROLL so I could put it in the "sides" still not sure what to put in there.. also shown my flyback driver(done in IRFP250) in its board.. together with the DC flybaCK and my cap...






starting to look like a tesla coil hahaha

Re: my secondary coil, is this OK?
Coronafix, Tue Sept 01 2009, 07:20AM

The output of your flyback will be DC. This changes things somewhat as you will need a charging reactor.

Someone correct me if I'm wrong here.

Re: my secondary coil, is this OK?
Steve Conner, Tue Sept 01 2009, 09:22AM

In practice, people seem to just hook the output of a DC flyback across the spark gap of a Tesla tank circuit and it works fine. The flyback is naturally current-limited so it charges capacitors happily.

Re: my secondary coil, is this OK?
raff, Tue Sept 01 2009, 10:22AM

guys,

can someone pls explain whats the importance of adjusting the sparkGAP? is it part of the fine-tuning process?

Re: my secondary coil, is this OK?
Coronafix, Tue Sept 01 2009, 10:43PM

The adjustment of the sparkgap is for setting the voltage that the cap will charge to. The spark will jump across the gap when it gets to a certain voltage.

Re: my secondary coil, is this OK?
raff, Tue Sept 01 2009, 11:31PM

I see.. I charged the home made cap(7.8nF) with 80watt flyback driver, it gave out max NOISE(bang) with 4mm gap distance, beyond that, no more arking.. higher GAP, lower charge-discharge cycle, lower gap (say 1-2mm) results in faster charge-discharge cycle... Thanks

Re: my secondary coil, is this OK?
raff, Wed Sept 02 2009, 07:29AM

almost done



blower or sucker? its from a cheap hair dryer...


still working on that fan motor(for gap) and the topload... otherwise, its done...
(mod edit: oversized pics cruelly squidged! Edit your post to see how)

Re: my secondary coil, is this OK?
raff, Wed Sept 02 2009, 09:31AM

guys,

does the topload HEAT up during operation? If I cant find a metal or aluminum duct, maybe I will use a plastic ang WRAP it with many layers of aluminum foil..

Re: my secondary coil, is this OK?
Mads Barnkob, Wed Sept 02 2009, 01:29PM


There should be no significant heating on the topload on such a small flyback driven SGTC, unless you draw an arc closely for some period.

I have only experienced real heating on the topload, where it felt warm to the hand, when running 3kW CW mode on a SSTC.

Re: my secondary coil, is this OK?
Coronafix, Wed Sept 02 2009, 11:15PM

You should turn that hairdryer around so that it blows between the gaps.
If your primary is solid copper, then you could strip the insulation and tap it where you want to.

Re: my secondary coil, is this OK?
raff, Thu Sept 03 2009, 12:25AM

guys,

made a 1st run.. primary used was that shown in photo.. inner diameter was 4.4" and spark gap no BLOWER yet.. powered it up with 12w flyback driver..it works! but I had to draw the arc going >> to the GND end of the secondary..or there is arcing between primary and secondary(w/c has OD of 3")... I have also seen that there is MORE output with topload compared to NO topload... with 12watt power from flyback driver, I could draw 1cm spark from it(no tesla connection).... with the tesla connected and running, I could get close to 1.5" (with topload) using the Hv out of the secondary and its GND connection...

this morning, I have integrated the hair dryer motor(as blower) to the gap..done! and I have REdone my coil (just expanded it only) so I could make 6" ID coil..resulting in 4.5T total.... I did THIS so there will be no arcing between primary and secondary... here are the results:

flyback driver = 78watts
WITH topload I just get 1.5" arcs (to GND connection)????
no topload, I could get 2-3" arcs (to GND)
but arcs are kinda THIN...

this means its seriously detuned, right?

I had better results with the 4.3" diamter primary than this 6" diameter primary...


EDIT:
after a few hours of tweaking, I made a new primary coil , flat pancake but looks like a cone
I think its in tune now, 5T for the primary and had to put up again my topload.. powered it up with my zvs@320watts, and bwweeeeeeewww there goes the noise.. with spark gap of 1mm, arcs(to gnd) are fast continouos, can reach to 4 or 5" in length..with gaps of about 4mm, I get whiter sparks(and longer too,about 6-7").. but its MORE noisy than ever, and I seem to have prob with my home made cap, the internal aluminum sheet sometimes arc to the connecting wire.. need to make another one with smaller foil dimensions... with 1mm of gap, my cap SEEMS to conk out.. dunno how to call it, seems like it would want to fire or not, something like that, and output seems a bit diminishing when this happens..

ill post video of this soon.. once we get clear skies here...

Re: my secondary coil, is this OK?
raff, Sun Sept 06 2009, 10:59AM

guys,

is this normal behaviour?

#1> when SGTC is close to being in-tune, tank CAP (sort of) heats up a bit than when you where just off resonance?

#2> with my secondary coil resonating at around 680KHz, putting an IDEAL topload, what would be the final resonant freq? just an estimate pls

Re: my secondary coil, is this OK?
brtaman, Sun Sept 06 2009, 11:39AM

Hey raff,

Nice project you are working on, using a blow-dryer is a good idea, it worked great for me on my flyback TC. As coronafix mentioned, you want it blowing on the spark gap.

To answer your question about the spark gap tunning, in the case of flyback SGTC's (have yet to make an AC charged SGTC), the tuning of the spark gap does have an effect on the tuning. Particularly, the higher the BPS (smaller gap width) the longer the streamers. I have noticed in my case when I was doing a final tune that changing the primary geometry (adding and subtracting turns) affects the BPS of the system so I had to adjust the spark gap for a given amount of primary. I believe that this is mainly due to the coupling coefficient and ring-up, as they affect the transfer of energy from primary to secondary.

Also the FKP-1s in my coil do seem to heat up quite a bit when running for 15 minutes+.

Please post up some vids when you are done, I really want to see what 320W of flyback input power does in action. :) Is the flyback ZVS driven?


Thanks
brtaman

Re: my secondary coil, is this OK?
raff, Sun Sept 06 2009, 12:42PM

Hi brtaman

yup its flyback zvs driven (40Vdc@8A) ... I could get almost 8" arcs to GND with the SGTC.... I do FINALLY see arcs (on the topload) even with a non-proper grounding of the secondary :) 3 meters of gnd wire still NOT connected to EARTH ground... but its better now than before.. note: I have been DOING the tuning on morning/afternoon only (outdoors) so sparks are a bit hard to see(or thin looking).. cant do it YET on evenings (SGTC are notoriously noisy)..

I changed again my primary to using 0.04" diameter HOOKUP wire (helical = 9T/4.2" ID about 19uH inductance), this has much better coupling than with the flat pancake style.. though I lowered it up a bit becuase of arcover with pri/sec.. I know pictures say more than words BUT.. dont worry i will post tommorow...

right now im just a bit frustrated (though its my part to blame) because I have to make another tank cap (mine was from hvwiki).. two times I have made but I used fewer sheets of transparency to upper the capacitance, after a few runs (few minutes actually)with the SGTC (w/c happen to be almost tuned) it died..but it DID work as expected...

this time Im going to REALLY FOLLOW those 15 sheets transparency total.. mine was only totalling 5 sheets

and maybe ill have to redo my blown spark gap, maybe ADD another metal in-between(to make up a series SG for a better quenching...

one more thing I noticed, SGTC doesnt really need high amperage input(from zvs) but wants HIGHER voltage.. that is what I have noticed... flyback driven zvs with 15V @2A has more Hv output (on sgtc) than 12V @ 6A...

till then..

Re: my secondary coil, is this OK?
brtaman, Sun Sept 06 2009, 01:23PM

Hey,

You really should ground the secondary. You will be in for quite a surprise performance wise. ;)

I agree SGTC's are VERY loud, but flyback SGTC's are even worse I think, my TC screams like an angry banshee. Earplugs are mandatory.


I think the main reason you are not seeing larger streamer/high performance when upping the voltage input is that you are limited by your cap size. Even though you are applying more power, all that is doing is charging up the cap quicker and effectively increasing your BPS, the bang energy is remaining constant, with extra caps you will increase your bang energy greatly, but with the increased supply of power the caps will still "fill" at a BPS similair to now, which will in turn increase your coils performance drastically. I suggest making an extra two three caps and hooking them up one at a time while increasing voltage input.

Anyway enjoy your project, building them is the fun part imo.

Re: my secondary coil, is this OK?
raff, Mon Sept 07 2009, 05:56AM

hello again,

finally done rolling up my cap (w/c measured 2nF only, seems like my transparency sheets<different make> are more thicker than what Ive previously used).. made also a new primary just to compensate for the lower capacitance on the LC tank.. ID of 4.2" with 14T total = about 30uH...

NOTE: this is far from being TUNED.. just made a video of it for fear of the tank CAP being busted again during tuning...

pics

the whole steup, NOTE still no RF ground YET


my flyback (zvs) driver


my spark gap set to 3.5mm with blower from hair dryer


my home made cap, third times the charm!! 2nF


primary coil, 1mm dia, stranded copper wire


here is my topload, with a breakout point using cutter blade clamped by the two stainless plates


my MAGIC WAND again, still no RF ground YET..


VIDEO:




and I have a question:
with the current setup, WITH TOPLOAD, I get 5-6" arcs to GND..arcs are WHITE and thick.... now with the topload removed, I get "wilder" violet arcs and are LONGER.. what does this mean?

Re: my secondary coil, is this OK?
raff, Mon Sept 07 2009, 10:57AM

I tried using crumpled foil as topload... here are some images and video..








video


WHEW! Its time to stop rolling for caps now... its the third time my cap gets DEAD.. the 3rd cap I made gave good *RESULTS* dying..

any info for a more robust CAP?

Re: my secondary coil, is this OK?
brtaman, Mon Sept 07 2009, 05:48PM

Nice coil raff it is really coming together. :)

You are getting 2nF out of those caps? I really suggest that you make at least two extra caps to get you capacitance up to ~6nF. My coil seems to run it's best with 5nF and this is with 120W input (though I have a feeling it could handle more) With all the extra power input you will have at 300+W you should really look for going into the >10nF range.

Have you looking into buying MMC caps? With the high input powers of your coil you will really have to over-engineer your homemade caps to survive more than a few runs. However, I am not an expert on home-made cap durability though (the only time I made one was for a TEA laser a while back, which was not exactly a durable item to say the least)...so its just a guess, perhaps members with more experience on this topic could chime in?

Re: my secondary coil, is this OK?
raff, Mon Sept 07 2009, 06:03PM

Thanks man!

while CAP is DEAD, I have been "fooling" around with TeslaMap5<nice program btw>, and you know what? I WAS in tune with 14-15 turns with my primary and 2nF (for tank) in resonance with my secondary coil (with rolled aluminum foil ball 3")

so thats why its "corona" was reaching out.. note though, still no proper RF ground for that thing, just the loose 3 meter wire .. length of corona more than 3" (secondary coil 3" dia x 8.5" length) ... length of arc to ground I think was 6-7" now.. until my home made cap *dieD*

anyways, maybe (just maybe) i will have a go again with home made HV cap (leyden jar perhaps??) still looking for right materials...

about buying proper capacitors, I think thats very hard (near impossible) I dont own a credit card so I cant order parts outside our country...

but hey, this is a nice experience though.. making a SGTC , and fylback driven... It was my childhood dream that one day I will make a "thunder lightning generating device" hehehe and I finally DID it!

OT:
maybe ill consider making an SSTC , still not sure what "clocker" to use but for starters, I will have to use half-bridge maybe, we have IRFP450 locally available so I can use THAT.. line here is 220Vac 60Hz

Cheers!

sorry capacitor, maybe next time