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Help! My coil almost works

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LAN_403

Zorink

Thu Aug 07 2008, 08:20PM

Registered Member #1292 Joined: Wed Feb 06 2008, 04:09AM
Location: Mesa, AZ
Posts: 25

I've been building a coil and can't seem to get the arc to break out into air. I tuned it with an o-scope but it just won't arc into air.
Any ideas would be greatly appreciated.

Here are some pics and a video

GluD

Thu Aug 07 2008, 08:51PM

Registered Member #1221 Joined: Wed Jan 09 2008, 06:17PM
Location: Odense, Denmark
Posts: 196

Im sorry to inform you but none of the links apears to work.

Zorink

Thu Aug 07 2008, 08:56PM

Registered Member #1292 Joined: Wed Feb 06 2008, 04:09AM
Location: Mesa, AZ
Posts: 25

links fixed

Mates

Thu Aug 07 2008, 09:04PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

It is strange, I can get more power from my Iggy based little coil...There must be something terribly wrong. I would start with checking the output of your NST, than your caps and if everything fine it must be the tuning.
BTW: your coil looks very profi... Good work !

Good luck...

Zorink

Thu Aug 07 2008, 09:05PM

Registered Member #1292 Joined: Wed Feb 06 2008, 04:09AM
Location: Mesa, AZ
Posts: 25

Here are my specs from TeslaMap

---------------------------------------- ---------

--- Power Supply ---
NST V Out 12 kV
NST I Out 30 mA
Input V 120 V
Input F 60 Hz
NST VA 360.0
NST Watts 371.4 W
NST Impedance 400 Kohms
Max Arc 32.8 in
NST PFC Cap 66.3 uF

--- Primary Capacitor ---
Your Cap 9.38 nF
Resonate Cap 6.6 nF
LTR Static Cap 9.3 nF
LTR Sync Cap 12.6 nF

--- Secondary Coil ---
Heavy build magnet wire
Wire AWG 24 AWG
Wire Length 1,031.6 ft
Wire Weight 1.26 lbs
Wire Resistance 26.5 ohms
Secondary Height 22 in
Secondary Diameter 4 in
H/W Ratio 5.5 : 1
Turns 985.6
Secondary L 16.16 mH
Secondary C 8.37 pF

--- Top Load ---
Overall Diameter (1) 12 in
Ring Diameter (1) 3 in
Overall Diameter (2) unknown
Ring Diameter (2) unknown
Sphere Diameter unknown
Top Load Adjust 95 %
Top Load C 14.26 pF

--- Top Load + Secondary ---
Resonate F 263.17 kHz

--- Primary ---
Wire Diameter .25 in
Wire Spacing .25 in
Hole Diameter 6 in
Coil Angle unknown
Coil Adjust 95 %

Needed primary inductance with:
Your Cap 24.50 uH
Resonate Cap 34.65 uH
LTR Static Cap 24.75 uH
LTR Sync Cap 18.24 uH

Zorink

Thu Aug 07 2008, 09:15PM

Registered Member #1292 Joined: Wed Feb 06 2008, 04:09AM
Location: Mesa, AZ
Posts: 25

Other details:

12000 volt 30 mA Franceformer non gfci
MMC is (16) CDE 942 capacitors with 10 meg-ohm 1/2 watt bleed resistors on each cap
Terry filter (see attached image) built for 12 kV
RF filter is a 2x20 amp Hopkins line filter

Zorink

Thu Aug 07 2008, 09:20PM

Registered Member #1292 Joined: Wed Feb 06 2008, 04:09AM
Location: Mesa, AZ
Posts: 25

Mates wrote ...

It is strange, I can get more power from my Iggy based little coil...There must be something terribly wrong. I would start with checking the output of your NST, than your caps and if everything fine it must be the tuning.
BTW: your coil looks very profi... Good work !

Good luck...

Thanks for the compliment.
How would I go about checking those things (12kV would kill my pocket multimeter)? I'm fairly certain it's not the tuning though, I checked it twice with an o-scope and a frequency generator.

Coronafix

Thu Aug 07 2008, 09:47PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Spark loading lowers the resonant frequency, so the only way to tune a coil is manually.
You have found the spot with your oscope, I suggest moving your tap point outwards until you get the longest sparks.
By the looks of it, it's just out of tune.
I hope you have enough primary otherwise you will need to add capacitance.
Nice workmanship by the way, it looks like you've taken your time with it which is always nice to see.

Ultra7

Thu Aug 07 2008, 11:08PM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

It looks like your strike rail is one complete loop, if this is the case, then it is robbing you of power.
Chop out a section of it to make it an incomplete loop, otherwise the coil thinks it is a shorted turn.

Then on to tuning.

Begin tuning it where your program tells you to start, then run it for a few seconds to see where your sparks are.
If no sparks, then turn everything off, move out one turn, and try again.
Once you get to where the sparks start to break out, turn everything off again, move out one more turn and see if they got bigger.
If so then keep moving out till the sparks start to get smaller.
Once they get smaller, move back a turn and then start bringing your tap point in or out in quarter intervals till you find the sweet spot.
Once your sweet spot is found, then move it in eighths till you find the best position. . . and so on till you are as tuned as you can be.

Adding a breakout point makes this process easier.

Once you find the optimal tuning point, then the breakout point can be removed.

Putting things on top of the toroid will change the capacitance, so if you plan to cover a paper mache skull with Al tape and put it on top of it for a Halloween prop, it will require minor retuning. Also, changing the top load will also require a small re-tune.

Hope this helps.

ArcLight

Fri Aug 08 2008, 12:22AM

Registered Member #341 Joined: Thu Mar 23 2006, 07:41PM
Location: Northern Illinois, USA
Posts: 69

Very nice build job, clearly you take pride in your work. But, your gap sucks (if I may be so blunt.) Of all the static gap designs, I like that one least. I don't believe that you can get enough air through it (at least not with a squirrel cage) to make it quench properly, and if the gap doesn't quench properly then your coil will almost run. Just for a test try using an air compressor instead. I bet you end up with a different gap design and a fine running coil.

Edit to add: You could make several more gaps of the same design and place them in series in front of your blower.

Regards, ArcLight

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