Coil decision
Michael W., Thu Mar 22 2007, 07:40PMSo, Dilemma. I have a 4.5" X 22.5" Coil and a 3" X 18" coil all varnished up and ready to use. I'm planning on using one of these with a 900W NST and an MMC, the question is if I choose the larger coil, will that give me larger arcs or am I better to stick with the smaller coil? and on a side note I already made the primary to suit the 3" coil but theres a lot of extra turns, will the tuning position change a lot outwards if I use the 4" coil or should I be good? Its alot of questions but I'm itching to get building....
Re: Coil decision
Part Scavenger, Thu Mar 22 2007, 08:23PM
You'll probably get the same length with both secondaries depending on the constuction, # of turns, etc. The sparks will look bigger on the smaller one. The last question, I'm not sure about with the information you gave us, plug your numbers into TeslaCAD or something. That should tell you.
Part Scavenger, Thu Mar 22 2007, 08:23PM
You'll probably get the same length with both secondaries depending on the constuction, # of turns, etc. The sparks will look bigger on the smaller one. The last question, I'm not sure about with the information you gave us, plug your numbers into TeslaCAD or something. That should tell you.
Re: Coil decision
Marko, Thu Mar 22 2007, 08:33PM
Hi Michael!
I think the smaller one is fine since your max expected spark length is just around 3 lengths
(54''). And sparks will looke better on a smaller coil.
What are resonant frequencies of these two?
Marko, Thu Mar 22 2007, 08:33PM
Hi Michael!
I think the smaller one is fine since your max expected spark length is just around 3 lengths
(54''). And sparks will looke better on a smaller coil.
What are resonant frequencies of these two?
Re: Coil decision
Michael W., Thu Mar 22 2007, 08:53PM
Hi Marko! Well the resonant frequency of the Larger coil is 254.63Khz and the other one is 495.16Khz. I did want to use a larger coil so it would balance out the larger base I made for the whole thing but if they're both going to produce the same arc length then I might as well use the smaller coil...
Michael W., Thu Mar 22 2007, 08:53PM
Hi Marko!
Well the resonant frequency of the Larger coil is 254.63Khz and the other one is 495.16Khz. I did want to use a larger coil so it would balance out the larger base I made for the whole thing but if they're both going to produce the same arc length then I might as well use the smaller coil...Re: Coil decision
Sulaiman, Thu Mar 22 2007, 09:15PM
Roughly speaking, the larger the TC the more efficient it is. (arc length) / (input power)
i.e. I would expect a larger arc with the larger coil.
It's not proportional though, so as noted above the smaller coil would appear more impressive.
Sulaiman, Thu Mar 22 2007, 09:15PM
Roughly speaking, the larger the TC the more efficient it is. (arc length) / (input power)
i.e. I would expect a larger arc with the larger coil.
It's not proportional though, so as noted above the smaller coil would appear more impressive.
Re: Coil decision
Marko, Thu Mar 22 2007, 09:18PM
Most importantly, larger secondary with lower frequency will allow to use much bigger primary for same bang energy, reducing peak current and losses.
Frequency of the smaller one here looks a bit high, but I guess topload can fix it.
I think you'l be able to push him well enough to start flashing over anyway..
Marko, Thu Mar 22 2007, 09:18PM
Most importantly, larger secondary with lower frequency will allow to use much bigger primary for same bang energy, reducing peak current and losses.
Frequency of the smaller one here looks a bit high, but I guess topload can fix it.
I think you'l be able to push him well enough to start flashing over anyway..
Re: Coil decision
sparky, Fri Mar 23 2007, 01:54AM
~ they will perform nearly identically... its all about looks.
sparky, Fri Mar 23 2007, 01:54AM
~ they will perform nearly identically... its all about looks.
Re: Coil decision
Part Scavenger, Sat Mar 24 2007, 02:40AM
What's wrong with high peak currents? That's what you want! The goal is to get the current as high as possible as quickly as possible without flashover or exploding something, and have the spark gap quench so that all that power is quickly delivered to the coil and then trapped. Lower inductance (therefore higher capacitance) should get you bigger sparks. BUT, like Marko said you will waste more in the primary with higher current, and more inductance will have better coupling. Trick is to find the middle, I generally don't worry about it that much, I usually just give my power supply the capacitance it can handle, then build the primary accordingly. About the topload, I think I'd put one on that drops the frequency about 1/2.
About the secondary, *technically* you should get longer sparks with it. Because it has a lower resonant frequency, it will probably be more efficient. I honestly don't know how much, but output will be comparable. Personally, I would go with the smaller coil, because even though you may gain an inch with the bigger one, it won't look bigger.
Part Scavenger, Sat Mar 24 2007, 02:40AM
Firkragg wrote ...
Most importantly, larger secondary with lower frequency will allow to use much bigger primary for same bang energy, reducing peak current and losses.
Frequency of the smaller one here looks a bit high, but I guess topload can fix it.
I think you'l be able to push him well enough to start flashing over anyway..
Most importantly, larger secondary with lower frequency will allow to use much bigger primary for same bang energy, reducing peak current and losses.
Frequency of the smaller one here looks a bit high, but I guess topload can fix it.
I think you'l be able to push him well enough to start flashing over anyway..
What's wrong with high peak currents? That's what you want! The goal is to get the current as high as possible as quickly as possible without flashover or exploding something, and have the spark gap quench so that all that power is quickly delivered to the coil and then trapped. Lower inductance (therefore higher capacitance) should get you bigger sparks. BUT, like Marko said you will waste more in the primary with higher current, and more inductance will have better coupling. Trick is to find the middle, I generally don't worry about it that much, I usually just give my power supply the capacitance it can handle, then build the primary accordingly. About the topload, I think I'd put one on that drops the frequency about 1/2.
About the secondary, *technically* you should get longer sparks with it. Because it has a lower resonant frequency, it will probably be more efficient. I honestly don't know how much, but output will be comparable. Personally, I would go with the smaller coil, because even though you may gain an inch with the bigger one, it won't look bigger.
Re: Coil decision
Marko, Sat Mar 24 2007, 10:41AM
Well, Q factor of the primary alone, not counting the secondary, is 1/R sqrt(L/C), y?
Your surge impedance is sqrt(L/C), so your peak willl be proportional to ratio of your inductance and capacitance!
You could easily get humongous peak currents in your primary by charging a huge capacitor at low voltage and discharging into a single turn primary, wich intuitively doesn't look like a well designed tesla coil!
Massive primary current will not do anything except creating huge losses on spark gap and require us to increase coupling to transfer most energy to secondary before it's lost.
High coupling often leads to flashovers, and, more importantly, current will heterodyne much faster, making it very difficult to quench properly with a gap that is already torched with massive current.
So, you just want as big as possible surge impedance. Secondary itself seems to have little importance about losses.
It was all well explained on richie burnett's site
And some questions are answered here
Before I baffle everything with hardcore TC theory, just design your cap after your power supply and your primary after your secondary... don't be afraid to use larger topload and more primary turns.
Marko, Sat Mar 24 2007, 10:41AM
What's wrong with high peak currents? That's what you want! The goal is to get the current as high as possible as quickly as possible without flashover or exploding something, and have the spark gap quench so that all that power is quickly delivered to the coil and then trapped. Lower inductance (therefore higher capacitance) should get you bigger sparks. BUT, like Marko said you will waste more in the primary with higher current, and more inductance will have better coupling. Trick is to find the middle, I generally don't worry about it that much, I usually just give my power supply the capacitance it can handle, then build the primary accordingly. About the topload, I think I'd put one on that drops the frequency about 1/2.
Well, Q factor of the primary alone, not counting the secondary, is 1/R sqrt(L/C), y?
Your surge impedance is sqrt(L/C), so your peak willl be proportional to ratio of your inductance and capacitance!
You could easily get humongous peak currents in your primary by charging a huge capacitor at low voltage and discharging into a single turn primary, wich intuitively doesn't look like a well designed tesla coil!
Massive primary current will not do anything except creating huge losses on spark gap and require us to increase coupling to transfer most energy to secondary before it's lost.
High coupling often leads to flashovers, and, more importantly, current will heterodyne much faster, making it very difficult to quench properly with a gap that is already torched with massive current.
So, you just want as big as possible surge impedance. Secondary itself seems to have little importance about losses.
It was all well explained on richie burnett's site
And some questions are answered here
Before I baffle everything with hardcore TC theory, just design your cap after your power supply and your primary after your secondary... don't be afraid to use larger topload and more primary turns.
Re: Coil decision
Part Scavenger, Sat Mar 24 2007, 09:40PM
Ok, that is a very good point. Sorry.
Part Scavenger, Sat Mar 24 2007, 09:40PM
Ok, that is a very good point. Sorry.
Re: Coil decision
Michael W., Sun Mar 25 2007, 11:07PM
So the first light of this coil was quite anti-climactic. The most I could squeeze out of it was about 5 or 6". This is the part I hate most about tesla coiling, he effort put into building and then the tuning frustration. I have a capacitor thats nicely matched to the transformer. So whats everyones first thing they do when tuning a coil? I have an oscilloscope but no frequency generator. Does anyone know an Easy DIY func. Generator? That might make it easier...
Michael W., Sun Mar 25 2007, 11:07PM
So the first light of this coil was quite anti-climactic. The most I could squeeze out of it was about 5 or 6". This is the part I hate most about tesla coiling, he effort put into building and then the tuning frustration. I have a capacitor thats nicely matched to the transformer. So whats everyones first thing they do when tuning a coil? I have an oscilloscope but no frequency generator. Does anyone know an Easy DIY func. Generator? That might make it easier...
Re: Coil decision
Hazmatt_(The Underdog), Mon Mar 26 2007, 03:24AM
If you hate tuning the system and trying to find its optimal point by hit or miss evaluation, the other choice is to get the equipment you need to make measurements. Having an oscilloscope is important, and you can get a good old HP tube generator for pretty cheap, and you're set for the most part. I've spent a lot of money on gear for measurement and it hasn't been easy or cheap.
Scope, generator and LCR meter are the essentials in this game if you want big sparks.
If you want transfer functions, power, and analysis, you have to bite a pretty big bullet and get a DSO of some sort. I've even considered buying a Spectrum Analyzer kit for $300.
This is an expensive hobby, and if you can get away with manual tuning I'd be happy with that, otherwise you're in for some nasty sticker shock.
Hazmatt_(The Underdog), Mon Mar 26 2007, 03:24AM
If you hate tuning the system and trying to find its optimal point by hit or miss evaluation, the other choice is to get the equipment you need to make measurements. Having an oscilloscope is important, and you can get a good old HP tube generator for pretty cheap, and you're set for the most part. I've spent a lot of money on gear for measurement and it hasn't been easy or cheap.
Scope, generator and LCR meter are the essentials in this game if you want big sparks.
If you want transfer functions, power, and analysis, you have to bite a pretty big bullet and get a DSO of some sort. I've even considered buying a Spectrum Analyzer kit for $300.
This is an expensive hobby, and if you can get away with manual tuning I'd be happy with that, otherwise you're in for some nasty sticker shock.
Re: Coil decision
Michael W., Mon Mar 26 2007, 03:51AM
Its not necessarily that I don't like the manual tuning, its that up to this point I've never been overly successful with doing it by hand...
Michael W., Mon Mar 26 2007, 03:51AM
Its not necessarily that I don't like the manual tuning, its that up to this point I've never been overly successful with doing it by hand...
Re: Coil decision
Hazmatt_(The Underdog), Mon Mar 26 2007, 05:06AM
I wasn't very successful without an LCR meter either, but there are ways of manual tuning that are pretty fast, like choosing a turn then jumping 1 turn out and 1 turn in and seeing what does better.
Knowing your supply, capacitor, pri and sec. are the major keys, and that's where LCR meters excel.
By use of the LCR meter, simulation, and careful testing, you'll be able to get some nice long arcs from that supply, close to 5 feet or more.
Hazmatt_(The Underdog), Mon Mar 26 2007, 05:06AM
I wasn't very successful without an LCR meter either, but there are ways of manual tuning that are pretty fast, like choosing a turn then jumping 1 turn out and 1 turn in and seeing what does better.
Knowing your supply, capacitor, pri and sec. are the major keys, and that's where LCR meters excel.
By use of the LCR meter, simulation, and careful testing, you'll be able to get some nice long arcs from that supply, close to 5 feet or more.
Re: Coil decision
Steve Conner, Mon Mar 26 2007, 01:03PM
I've never owned an LCR meter and have sparked my own height and then some. I found an analog scope and signal generator were about all I needed. Tesla coiling is a pretty cheap hobby, compared to motor racing or yachting.
Steve Conner, Mon Mar 26 2007, 01:03PM
I've never owned an LCR meter and have sparked my own height and then some. I found an analog scope and signal generator were about all I needed. Tesla coiling is a pretty cheap hobby, compared to motor racing or yachting.
Re: Coil decision
Terry Fritz, Mon Mar 26 2007, 08:11PM
Hi,
Bart's JAVATC can probably tune your coil by computer calculation better than most test equipment.
You will have to figure it out (pretty easy) and measure things pretty carefully with a ruler. But once the input numbers are correct, the primary tuning and all outputs will be very accurate.
The program is pretty easily capable of calculating coil parameters better than most typical test equipment can measure!! It's also free, and just a mouse click away
Cheers,
Terry
Terry Fritz, Mon Mar 26 2007, 08:11PM
Hi,
Bart's JAVATC can probably tune your coil by computer calculation better than most test equipment.
You will have to figure it out (pretty easy) and measure things pretty carefully with a ruler. But once the input numbers are correct, the primary tuning and all outputs will be very accurate.
The program is pretty easily capable of calculating coil parameters better than most typical test equipment can measure!! It's also free, and just a mouse click away
Cheers,
Terry
Re: Coil decision
Michael W., Tue Mar 27 2007, 03:34AM
Ok, so JavaTC newb here...I spent about an hour and measured everything pretty accurately...but when I told it to auto tune it said to check my primary parameters and to possibly change my capacitor value. So I'm going to post my inputs of the whole thing WARING: Its a lot. Any input on tuning etc. would be appreciated.
J A V A T C v.10 - CONSOLIDATED OUTPUT
Monday, March 26, 2007 8:25:36 PM
Units = Centimeters
Ambient Temp = 68°F
------------------------------------------- ---------
Surrounding Inputs:
------------------------------------------ ----------
290 = Ground Plane Radius
290 = Wall Radius
250 = Wall Height
290 = Ceiling Radius
250 = Ceiling Height
------------------------------------------ ----------
Secondary Coil Inputs:
------------------------------------------ ----------
Current Profile = G.PROFILE_LOADED
3.81 = Radius 1
3.81 = Radius 2
122 = Height 1
170 = Height 2
473.63 = Turns
25 = Wire Awg
--------------------------------------------- -------
Primary Coil Inputs:
------------------------------------------ ----------
9 = Radius 1
10.405 = Radius 2
125 = Height 1
125 = Height 2
1.0039 = Turns
0.5 = Wire Diameter
0.015 = Primary Cap (uF)
164 = Total Lead Length
0.3 = Lead Diameter
---------------------------------------- ------------
Top Load Inputs:
------------------------------------------ ----------
Toroid #1: minor=6.5, major=26, height=185, topload
----------------------------------------- -----------
Secondary Outputs:
----------------------------------------- -----------
830.98 kHz = Secondary Resonant Frequency
90 deg° = Angle of Secondary
48 cm = Length of Winding
9.87 cm = Turns Per Unit
0.55879 mm = Space Between Turns (edge to edge)
113.38 m = Length of Wire
6.3:1 = H/D Aspect Ratio
12.04 ohms = DC Resistance
12558 ohms = Forward Transfer Impedance
12445 ohms = Reactance at Resonance
0.164 kg = Weight of Wire
2.384 mH = Les-Effective Series Inductance
2.259 mH = Lee-Equivalent Energy Inductance
2.519 mH = Ldc-Low Frequency Inductance
15.39 pF = Ces-Effective Shunt Capacitance
14.325 pF = Cee-Equivalent Energy Capacitance
23.356 pF = Cdc-Low Frequency Capacitance
0.115 mm = Skin Depth
10.1 pF = Topload Effective Capacitance
45.3 ohms = Effective AC Resistance
275 = Q
----------------------------------------------- -----
Primary Outputs:
----------------------------------------- -----------
790.21 kHz = Primary Resonant Frequency
4.91 % = Percent Detuned
0 deg° = Angle of Primary
61.2 cm = Length of Wire
0.9 cm = Average spacing between turns (edge to edge)
5.19 cm = Primary to Secondary Clearance
0.429 µH = Ldc-Low Frequency Inductance
0.01611 µF = Cap size needed with Primary L (reference)
2.277 µH = Lead Length Inductance
3.641 µH = Lm-Mutual Inductance
0.111 k = Coupling Coefficient
9.01 = Number of half cycles for energy transfer at K
5.66 µs = Time for total energy transfer (ideal quench time)
------------------------------------------- ---------
Transformer Inputs:
------------------------------------------ ----------
120 [volts] = Transformer Rated Input Voltage
15000 [volts] = Transformer Rated Output Voltage
60 [mA] = Transformer Rated Output Current
60 [Hz] = Mains Frequency
120 [volts] = Transformer Applied Voltage
0 [amps] = Transformer Ballast Current
0 [ohms] = Measured Primary Resistance
0 [ohms] = Measured Secondary Resistance
-------------------------------------- --------------
Transformer Outputs:
----------------------------------------- -----------
900 [volt*amps] = Rated Transformer VA
250000 [ohms] = Transformer Impedence
15000 [rms volts] = Effective Output Voltage
7.5 [rms amps] = Effective Transformer Primary Current
0.06 [rms amps] = Effective Transformer Secondary Current
900 [volt*amps] = Effective Input VA
0.0106 [uF] = Resonant Cap Size
0.0159 [uF] = Static gap LTR Cap Size
0.0277 [uF] = SRSG LTR Cap Size
166 [uF] = Power Factor Cap Size
21213 [peak volts] = Voltage Across Cap
75000 [peak volts] = Recommended Cap Voltage Rating
3.38 [joules] = Primary Cap Energy
3972.6 [peak amps] = Primary Instantaneous Current
110.1 [cm] = Spark Length (JF equation using Resonance Research Corp. factors)
---------------------------------------- ------------
Rotary Spark Gap Inputs:
------------------------------------------ ----------
0 = Number of Stationary Gaps
0 = Number of Rotating Electrodes
0 [rpm] = Disc RPM
0 = Rotating Electrode Diameter
0 = Stationary Electrode Diameter
0 = Rotating Path Diameter
---------------------------------------- ------------
Rotary Spark Gap Outputs:
----------------------------------------- -----------
= Presentations Per Revolution
[BPS] = Breaks Per Second
[kmh] = Rotational Speed
[ms] = RSG Firing Rate
[ms] = Time for Capacitor to Fully Charge
= Time Constant at Gap Conduction
[ms] = Electrode Mechanical Dwell Time
[%] = Percent Cp Charged When Gap Fires
[peak volts] = Effective Cap Voltage
[joules] = Effective Cap Energy
[peak volts] = Terminal Voltage
[power] = Energy Across Gap
[cm] = RSG Spark Length (using energy equation)
--------------------------------------- -------------
Static Spark Gap Inputs:
------------------------------------------ ----------
2 = Number of Electrodes
0.3 [cm] = Electrode Diameter
1.3 [cm] = Total Gap Spacing
----------------------------------------- -----------
Static Spark Gap Outputs:
----------------------------------------- -----------
1.3 [cm] = Gap Spacing Between Each Electrode
21213 [peak volts] = Charging Voltage
20766 [peak volts] = Arc Voltage
31948 [volts] = Voltage Gradient at Electrode
15974 [volts/cm] = Arc Voltage per unit
97.9 [%] = Percent Cp Charged When Gap Fires
9.217 [ms] = Time To Arc Voltage
108 [BPS] = Breaks Per Second
3.23 [joules] = Effective Cap Energy
671982 [peak volts] = Terminal Voltage
351 [power] = Energy Across Gap
129.7 [cm] = Static Gap Spark Length (using energy equation)
Michael W., Tue Mar 27 2007, 03:34AM
Ok, so JavaTC newb here...I spent about an hour and measured everything pretty accurately...but when I told it to auto tune it said to check my primary parameters and to possibly change my capacitor value. So I'm going to post my inputs of the whole thing WARING: Its a lot. Any input on tuning etc. would be appreciated.
J A V A T C v.10 - CONSOLIDATED OUTPUT
Monday, March 26, 2007 8:25:36 PM
Units = Centimeters
Ambient Temp = 68°F
------------------------------------------- ---------
Surrounding Inputs:
------------------------------------------ ----------
290 = Ground Plane Radius
290 = Wall Radius
250 = Wall Height
290 = Ceiling Radius
250 = Ceiling Height
------------------------------------------ ----------
Secondary Coil Inputs:
------------------------------------------ ----------
Current Profile = G.PROFILE_LOADED
3.81 = Radius 1
3.81 = Radius 2
122 = Height 1
170 = Height 2
473.63 = Turns
25 = Wire Awg
--------------------------------------------- -------
Primary Coil Inputs:
------------------------------------------ ----------
9 = Radius 1
10.405 = Radius 2
125 = Height 1
125 = Height 2
1.0039 = Turns
0.5 = Wire Diameter
0.015 = Primary Cap (uF)
164 = Total Lead Length
0.3 = Lead Diameter
---------------------------------------- ------------
Top Load Inputs:
------------------------------------------ ----------
Toroid #1: minor=6.5, major=26, height=185, topload
----------------------------------------- -----------
Secondary Outputs:
----------------------------------------- -----------
830.98 kHz = Secondary Resonant Frequency
90 deg° = Angle of Secondary
48 cm = Length of Winding
9.87 cm = Turns Per Unit
0.55879 mm = Space Between Turns (edge to edge)
113.38 m = Length of Wire
6.3:1 = H/D Aspect Ratio
12.04 ohms = DC Resistance
12558 ohms = Forward Transfer Impedance
12445 ohms = Reactance at Resonance
0.164 kg = Weight of Wire
2.384 mH = Les-Effective Series Inductance
2.259 mH = Lee-Equivalent Energy Inductance
2.519 mH = Ldc-Low Frequency Inductance
15.39 pF = Ces-Effective Shunt Capacitance
14.325 pF = Cee-Equivalent Energy Capacitance
23.356 pF = Cdc-Low Frequency Capacitance
0.115 mm = Skin Depth
10.1 pF = Topload Effective Capacitance
45.3 ohms = Effective AC Resistance
275 = Q
----------------------------------------------- -----
Primary Outputs:
----------------------------------------- -----------
790.21 kHz = Primary Resonant Frequency
4.91 % = Percent Detuned
0 deg° = Angle of Primary
61.2 cm = Length of Wire
0.9 cm = Average spacing between turns (edge to edge)
5.19 cm = Primary to Secondary Clearance
0.429 µH = Ldc-Low Frequency Inductance
0.01611 µF = Cap size needed with Primary L (reference)
2.277 µH = Lead Length Inductance
3.641 µH = Lm-Mutual Inductance
0.111 k = Coupling Coefficient
9.01 = Number of half cycles for energy transfer at K
5.66 µs = Time for total energy transfer (ideal quench time)
------------------------------------------- ---------
Transformer Inputs:
------------------------------------------ ----------
120 [volts] = Transformer Rated Input Voltage
15000 [volts] = Transformer Rated Output Voltage
60 [mA] = Transformer Rated Output Current
60 [Hz] = Mains Frequency
120 [volts] = Transformer Applied Voltage
0 [amps] = Transformer Ballast Current
0 [ohms] = Measured Primary Resistance
0 [ohms] = Measured Secondary Resistance
-------------------------------------- --------------
Transformer Outputs:
----------------------------------------- -----------
900 [volt*amps] = Rated Transformer VA
250000 [ohms] = Transformer Impedence
15000 [rms volts] = Effective Output Voltage
7.5 [rms amps] = Effective Transformer Primary Current
0.06 [rms amps] = Effective Transformer Secondary Current
900 [volt*amps] = Effective Input VA
0.0106 [uF] = Resonant Cap Size
0.0159 [uF] = Static gap LTR Cap Size
0.0277 [uF] = SRSG LTR Cap Size
166 [uF] = Power Factor Cap Size
21213 [peak volts] = Voltage Across Cap
75000 [peak volts] = Recommended Cap Voltage Rating
3.38 [joules] = Primary Cap Energy
3972.6 [peak amps] = Primary Instantaneous Current
110.1 [cm] = Spark Length (JF equation using Resonance Research Corp. factors)
---------------------------------------- ------------
Rotary Spark Gap Inputs:
------------------------------------------ ----------
0 = Number of Stationary Gaps
0 = Number of Rotating Electrodes
0 [rpm] = Disc RPM
0 = Rotating Electrode Diameter
0 = Stationary Electrode Diameter
0 = Rotating Path Diameter
---------------------------------------- ------------
Rotary Spark Gap Outputs:
----------------------------------------- -----------
= Presentations Per Revolution
[BPS] = Breaks Per Second
[kmh] = Rotational Speed
[ms] = RSG Firing Rate
[ms] = Time for Capacitor to Fully Charge
= Time Constant at Gap Conduction
[ms] = Electrode Mechanical Dwell Time
[%] = Percent Cp Charged When Gap Fires
[peak volts] = Effective Cap Voltage
[joules] = Effective Cap Energy
[peak volts] = Terminal Voltage
[power] = Energy Across Gap
[cm] = RSG Spark Length (using energy equation)
--------------------------------------- -------------
Static Spark Gap Inputs:
------------------------------------------ ----------
2 = Number of Electrodes
0.3 [cm] = Electrode Diameter
1.3 [cm] = Total Gap Spacing
----------------------------------------- -----------
Static Spark Gap Outputs:
----------------------------------------- -----------
1.3 [cm] = Gap Spacing Between Each Electrode
21213 [peak volts] = Charging Voltage
20766 [peak volts] = Arc Voltage
31948 [volts] = Voltage Gradient at Electrode
15974 [volts/cm] = Arc Voltage per unit
97.9 [%] = Percent Cp Charged When Gap Fires
9.217 [ms] = Time To Arc Voltage
108 [BPS] = Breaks Per Second
3.23 [joules] = Effective Cap Energy
671982 [peak volts] = Terminal Voltage
351 [power] = Energy Across Gap
129.7 [cm] = Static Gap Spark Length (using energy equation)
Re: Coil decision
Steve Conner, Tue Mar 27 2007, 10:49AM
Your resonant frequency is too high, so with the capacitor chosen to draw optimum power from the transformer, you only have about one primary turn. I guess you wound the secondary with too heavy a gauge of wire, or on too small a diameter of tube.
Steve Conner, Tue Mar 27 2007, 10:49AM
Your resonant frequency is too high, so with the capacitor chosen to draw optimum power from the transformer, you only have about one primary turn. I guess you wound the secondary with too heavy a gauge of wire, or on too small a diameter of tube.
Re: Coil decision
Marko, Tue Mar 27 2007, 11:32AM
I'm just wondering, how did you in the end come with 830kHz for your final resonant frequency? How did you get 500kHz at first time?
0.45mm is very thick wire, and with only 470 turns I'm not suprised that Fres is too high!
What is the gauge of other secondary? I just suspect you may have miscalculated it too!
Fres lower = better, and I wouldn't go with anything over 300kHz in your design.
100..200kHz should be perfect.
Marko, Tue Mar 27 2007, 11:32AM
I'm just wondering, how did you in the end come with 830kHz for your final resonant frequency? How did you get 500kHz at first time?
0.45mm is very thick wire, and with only 470 turns I'm not suprised that Fres is too high!
What is the gauge of other secondary? I just suspect you may have miscalculated it too!
Fres lower = better, and I wouldn't go with anything over 300kHz in your design.
100..200kHz should be perfect.
Re: Coil decision
Michael W., Tue Mar 27 2007, 02:20PM
Well both wire gauges on the Larger Coil/smaller coil are the same. For my first Calculations I used teslacad then I used JavaTC. I'm not exactly sure of the wire gauge... So I'm measuring with some rough calipers. Just to clear up any possible misunderstanding, This is all measured in CENTIMETERS. Should I try the bigger coil? I think the wire gauge is about 25 or 26 gauge. I don't know how I'd figure that out....
Michael W., Tue Mar 27 2007, 02:20PM
Well both wire gauges on the Larger Coil/smaller coil are the same. For my first Calculations I used teslacad then I used JavaTC. I'm not exactly sure of the wire gauge... So I'm measuring with some rough calipers. Just to clear up any possible misunderstanding, This is all measured in CENTIMETERS. Should I try the bigger coil? I think the wire gauge is about 25 or 26 gauge. I don't know how I'd figure that out....
Re: Coil decision
Hazmatt_(The Underdog), Tue Mar 27 2007, 05:32PM
Two things I'm going to point out that you need to think about right away:
1. You only list 2 electrodes for your spark gap.
I have done it that way for a low power coil, but this is 900W we're talking about here!
2. Use the static gap cap .015 or .016 for best performance even with a rotary. My research, simulations, and real TC testing showed me right away that the large .028 drops your output performance because it loads the transformer too much.
If you want more details, see Calculating LTR thread.
Hazmatt_(The Underdog), Tue Mar 27 2007, 05:32PM
Two things I'm going to point out that you need to think about right away:
1. You only list 2 electrodes for your spark gap.
I have done it that way for a low power coil, but this is 900W we're talking about here!
2. Use the static gap cap .015 or .016 for best performance even with a rotary. My research, simulations, and real TC testing showed me right away that the large .028 drops your output performance because it loads the transformer too much.
If you want more details, see Calculating LTR thread.
Re: Coil decision
Michael W., Wed Mar 28 2007, 05:10AM
Ok, so I upgraded my spark gap to a 5 electrode gap...I'm now getting 18-20" arcs. Now for more optimization...
Michael W., Wed Mar 28 2007, 05:10AM
Ok, so I upgraded my spark gap to a 5 electrode gap...I'm now getting 18-20" arcs. Now for more optimization...
Re: Coil decision
Hazmatt_(The Underdog), Wed Mar 28 2007, 07:20AM
One way to tell that you're way out of tune that I noticed is by listening to the gap. Now this is very very loud! So be careful! But if the gap fires and its really loud, and your spark length is really short, start moving your primary tap around a lot. I noticed that as you get closer to that 'sweet spot' the gap and the spark are about the same loudness relativily speaking. So if you have almost no noise coming from the arcs, and lots of bang from the gap, move your tap out more and more until the gap quiets down and the arcs start getting longer..and louder.
I know that sounds terribly crazy, its just what I've noticed from SGTC's. Your experience may vary.
Hazmatt_(The Underdog), Wed Mar 28 2007, 07:20AM
One way to tell that you're way out of tune that I noticed is by listening to the gap. Now this is very very loud! So be careful! But if the gap fires and its really loud, and your spark length is really short, start moving your primary tap around a lot. I noticed that as you get closer to that 'sweet spot' the gap and the spark are about the same loudness relativily speaking. So if you have almost no noise coming from the arcs, and lots of bang from the gap, move your tap out more and more until the gap quiets down and the arcs start getting longer..and louder.
I know that sounds terribly crazy, its just what I've noticed from SGTC's. Your experience may vary.
Re: Coil decision
Steve Conner, Wed Mar 28 2007, 09:56AM
It sounds crazy, but it makes sense. In a SGTC, most of the energy that doesn't make it to the output spark gets burnt in the primary spark gap. So as you get closer to being in tune, the streamers get bigger while the spark gap dims and quietens down.
The various kinds of pulsed solid-state coils (DRSSTC, OLTC, etc) recycle the unused energy for use in the next bang, instead of wasting it. They have to do it that way because the transistorized "spark gap" can't stand the losses that a real spark gap can. So when tuning these, you can see the current draw from the line reach a maximum when it's roughly in tune.
Steve Conner, Wed Mar 28 2007, 09:56AM
It sounds crazy, but it makes sense. In a SGTC, most of the energy that doesn't make it to the output spark gets burnt in the primary spark gap. So as you get closer to being in tune, the streamers get bigger while the spark gap dims and quietens down.
The various kinds of pulsed solid-state coils (DRSSTC, OLTC, etc) recycle the unused energy for use in the next bang, instead of wasting it. They have to do it that way because the transistorized "spark gap" can't stand the losses that a real spark gap can. So when tuning these, you can see the current draw from the line reach a maximum when it's roughly in tune.
Re: Coil decision
Michael W., Wed Mar 28 2007, 02:35PM
Well I'm getting 18ish" arcs and my sparkgap sounds like a cap gun going off every half a second. I wear hearing protection or my ears ring after but I think I'll try Hazmatt's tuning method next....
Michael W., Wed Mar 28 2007, 02:35PM
Well I'm getting 18ish" arcs and my sparkgap sounds like a cap gun going off every half a second. I wear hearing protection or my ears ring after but I think I'll try Hazmatt's tuning method next....
Re: Coil decision
Marko, Wed Mar 28 2007, 02:43PM
Have you tried that bigger secondary you have there?
Regarding the spark gap, it's best to completely remove the primary and mmc and set it so that your nst *just* barely arcs over it. Anything more is dangerous to the transformer if cap is close to resonant value.
Marko, Wed Mar 28 2007, 02:43PM
Have you tried that bigger secondary you have there?
Regarding the spark gap, it's best to completely remove the primary and mmc and set it so that your nst *just* barely arcs over it. Anything more is dangerous to the transformer if cap is close to resonant value.
Re: Coil decision
Terry Fritz, Wed Mar 28 2007, 07:27PM
Hi,
You may be having a problem with primary "Q". If the primary capacitance is high and the primary inductance is low, the primary circuit will not "ring" like a bell but rather "thud" like a rock.
Q = SQRT(L/C) / 3
Q should be at least 20.
In your case Q = SQRT ( 0.429e-6 / 0.01611e-6) / 3 = 1.7
That is a least an order of magnitude too low!!
Bart should put a "Low Q Warning" in his program since this is easy to miss... I see he does have secondary Q which is almost impossible to mess up...
If so, the primary inductor basically looks like a dead short to the primary capacitor and the current is very high and fast, thus the extremely loud bang. Getting 18 inches still is actually pretty good!!!
So you need more primary inductance since the cap size is sort of fixed by your transformer size. (Ignore the 75,000 Volt recommended cap rating (Based on one old time silly "rule"...)
So how to fix it...
A Q of say 30 is pretty good for "me":
30 = SQRT( L / 16e-9) / 3 Where L = 130uH !!
Fo would then be:
Fo = 1 / (2 x pi x SQRT (L x C) == 1 / (2 x pi x SQRT( 130e-6 x 16e-9) = 110kHz.
So you need a lot of turns on the primary basically.
You then need a lot of turns on the secondary and a big top load too to match the 110kHz of the primary.
You need a big top load like 25pF would be nice. Then you get thin wire and wind the secondary to get lots of turns (probably 1000 to 1500).
You can see my big coil here but it uses a rotary gap (different primary cap value (27nF):
There is also a formula sheet here with lots of calculation info where the programs get most of their equations:
For what you have now, do everything possible to make the top load "BIG". Add more top loads... The secondary needs to have a lower resonant frequency so you can use more primary turns to increase the primary Q... Using a smaller NST transformer that would have a much lower matched primary capacitor may actually do better than what you have now too. You need more L and less C.
Hope this helps and is not too confusing
Cheers,
Terry
Terry Fritz, Wed Mar 28 2007, 07:27PM
Hi,
You may be having a problem with primary "Q". If the primary capacitance is high and the primary inductance is low, the primary circuit will not "ring" like a bell but rather "thud" like a rock.
Q = SQRT(L/C) / 3
Q should be at least 20.
In your case Q = SQRT ( 0.429e-6 / 0.01611e-6) / 3 = 1.7
That is a least an order of magnitude too low!!
Bart should put a "Low Q Warning" in his program since this is easy to miss... I see he does have secondary Q which is almost impossible to mess up...
If so, the primary inductor basically looks like a dead short to the primary capacitor and the current is very high and fast, thus the extremely loud bang. Getting 18 inches still is actually pretty good!!!
So you need more primary inductance since the cap size is sort of fixed by your transformer size. (Ignore the 75,000 Volt recommended cap rating
(Based on one old time silly "rule"...)So how to fix it...
A Q of say 30 is pretty good for "me":
30 = SQRT( L / 16e-9) / 3 Where L = 130uH !!
Fo would then be:
Fo = 1 / (2 x pi x SQRT (L x C) == 1 / (2 x pi x SQRT( 130e-6 x 16e-9) = 110kHz.
So you need a lot of turns on the primary basically.
You then need a lot of turns on the secondary and a big top load too to match the 110kHz of the primary.
You need a big top load like 25pF would be nice. Then you get thin wire and wind the secondary to get lots of turns (probably 1000 to 1500).
You can see my big coil here but it uses a rotary gap (different primary cap value (27nF):
There is also a formula sheet here with lots of calculation info where the programs get most of their equations:
For what you have now, do everything possible to make the top load "BIG". Add more top loads... The secondary needs to have a lower resonant frequency so you can use more primary turns to increase the primary Q... Using a smaller NST transformer that would have a much lower matched primary capacitor may actually do better than what you have now too. You need more L and less C.
Hope this helps and is not too confusing
Cheers,
Terry
Re: Coil decision
Part Scavenger, Wed Mar 28 2007, 07:50PM
Matt's right about that tuning, you can tell by the way it sounds. You don't necessarily have to have your earplugs out to tell though. Apart from the streamer length, loudness he was talking about... the even-ness of the gap firing should tell you alot as well. Unfortunately, you kind of have to acquire "the ear" which isn't really hard to do, but like I was in your situation, I didn't know what to listen for until I had a coil that worked well.
Part Scavenger, Wed Mar 28 2007, 07:50PM
Matt's right about that tuning, you can tell by the way it sounds. You don't necessarily have to have your earplugs out to tell though. Apart from the streamer length, loudness he was talking about... the even-ness of the gap firing should tell you alot as well. Unfortunately, you kind of have to acquire "the ear" which isn't really hard to do, but like I was in your situation, I didn't know what to listen for until I had a coil that worked well.
Re: Coil decision
Marko, Wed Mar 28 2007, 08:00PM
Just to clarify myself after terry: Definitely, do use that bigger secondary you have, and put on as much topload as you can before the coil starts looking silly.
Try to get your frequency somewhere to 100..200kHz, lower = better!
You need as much primary inductance as possible because you are on very low end as me and terry have seemingly figured out!
Tuning isn't actually all that hard thing to do, you just get a figure from a calculator adn then
fiddle the tap by trial and error around it.
Increasing primary Q should be your priority now.
Marko, Wed Mar 28 2007, 08:00PM
Just to clarify myself after terry: Definitely, do use that bigger secondary you have, and put on as much topload as you can before the coil starts looking silly.
Try to get your frequency somewhere to 100..200kHz, lower = better!
You need as much primary inductance as possible because you are on very low end as me and terry have seemingly figured out!
Tuning isn't actually all that hard thing to do, you just get a figure from a calculator adn then
fiddle the tap by trial and error around it.
Increasing primary Q should be your priority now.
Re: Coil decision
Terry Fritz, Wed Mar 28 2007, 08:11PM
Oh! I see Firkragg "already" mentioned the Q thing I missed his earlier post, but the one turn primary caught my eye 
Looks like this is getting figured out See, we didn't need any test equipment after all
Cheers,
Terry
Terry Fritz, Wed Mar 28 2007, 08:11PM
Oh! I see Firkragg "already" mentioned the Q thing
I missed his earlier post, but the one turn primary caught my eye Looks like this is getting figured out See, we didn't need any test equipment after all Cheers,
Terry
Re: Coil decision
Michael W., Sun Apr 01 2007, 07:14PM
Alright I'm in business now. I've managed to get a function generator and a scope to tune with, I'm guessing first I'd like to find the Res. Freq. of the secondary so I hooked it up like its described here....
But when sweeping I don't seem to get a spike on the scope. Does anyone have a tried and true method of tuning with a scope?
Michael W., Sun Apr 01 2007, 07:14PM
Alright I'm in business now. I've managed to get a function generator and a scope to tune with, I'm guessing first I'd like to find the Res. Freq. of the secondary so I hooked it up like its described here....
But when sweeping I don't seem to get a spike on the scope. Does anyone have a tried and true method of tuning with a scope?
Re: Coil decision
Hazmatt_(The Underdog), Sun Apr 01 2007, 07:24PM
You won't get a spike, you get a dip. At resonance the signal will just about flatline on the scope because you have a divider network between the resistor and the tuned system.
You may get a couple of small dips after the fundamental too, those are harmonics, so be careful to watch for the first big dip in signal strength, that will be Fo.
Hazmatt_(The Underdog), Sun Apr 01 2007, 07:24PM
You won't get a spike, you get a dip. At resonance the signal will just about flatline on the scope because you have a divider network between the resistor and the tuned system.
You may get a couple of small dips after the fundamental too, those are harmonics, so be careful to watch for the first big dip in signal strength, that will be Fo.
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