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Registered Member #3395
Joined: Thu Nov 04 2010, 08:42AM
Location: Christchurch, New Zealand
Posts: 193
Hi there,
This is about my first SGTC which I will be making over this summer (here in NZ) for my school project and I have about 6 months to complete it. I'm completely new to everything about Tesla coils so basically I'm a noob. However, I have been looking at this website suggested by a friend of mine who has made a TC:
So far I've learnt about quenching, coupling, resonant rise, ring down and ring up, ballasting but what I'm generally finding is that this website is good for the fundamentals of TC physics but not really for how to make one. What I'm implying is that I need help with:
-working out the capacitance values required -how to tune the Tesla coil and what to use -how should I make my spark gap -how big my toroid should be
I understand the TC is a resonant circuit and that it has to be tuned correctly so basically I'm looking for any rules of thumb, techniques, mathematical equations to use, websites that may be of help etc Please do understand if I struggle with grasping the concepts and fundamentals, but as I said, this my first time and I will try my best. Don't be surprised if any more questions crop up along the way.
I really appreciate your help and I look forward to building this!
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
JavaTC is a great program to aid in the building of your TC. There are also others like wintesla and scantesla. Most of your equations will be done for you using a program like javaTC. Heres a great read for tuning theres also a YouTube video to go with it. And generally your toroid should be as wide as your TC is tall but it doesnt HAVE to be..
Another bit of equations to help you find capacitance, frequency, inductance, and more
There are lots of design guides you can find doing a quick google search. Good luck!
Registered Member #3395
Joined: Thu Nov 04 2010, 08:42AM
Location: Christchurch, New Zealand
Posts: 193
Thanks for your help and I will check these out when I get the chance. I understand the toroid has to be the correct size for the correct capacitance -> good streamer loading -> earlier quenching time etc. So is the "wide as tall" rule really true? Just confirming, that's all.
And also I understand the coupling should be between 0.05 - 0.2, so how can I apply this to my primary and secondary? Generally speaking, should I do the calculations then build it or build it then calculate?
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
The "wide as tall" thing is more a generality than a rule. I think it depends more on the type of primary you decide to make (helical, conical, flat) as the E fields of the LCp and LCs can influence one another. In the case of a TC I'd think the primary effects the secondary. Here is an artistic re-creation of what I'm talking about you would need some sort of EM field simulator software to see an accurate depiction of that but I dont think it is necessary at all. It is more so to design a secondary and toroid system that will make less strikes to primary. So unless you had that problem, it might not be needed. What I do is make my secondary and toroid, then find the frequency of that. Then I try to design my primary and tank cap so that it will match the frequency of the secondary. I try to avoid doing calculations and stuff so sometimes I mess around in javaTC plugging in different values here and there to find what works. But if you are doing this for a school project, doing the calculations yourself might be good for showing your work on the design. When it comes to coupling, I let the programs do the calculations for me. And if coupling is still a problem just use a little trial and error raising or lowering your secondary.
Registered Member #3395
Joined: Thu Nov 04 2010, 08:42AM
Location: Christchurch, New Zealand
Posts: 193
What about a variac that would be suitable (i.e: the correct power rating) for using this TC? I will be using a 15kV 30mA NST to power the primary so I calculated that 15kV @ 30mA = 450VA. Of course this value will be slightly different due to losses but this is a general figure.
My local electronics supplier has a variac that is rated for 500VA, therefore with a 50VA surplus. So, is the ~450VA output from the NST really going to be that value or will it fluctuate? If so, what would cause this? And should I get the variac at the local supplier?
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Jozef C wrote ...
What about a variac that would be suitable (i.e: the correct power rating) for using this TC? I will be using a 15kV 30mA NST to power the primary so I calculated that 15kV @ 30mA = 450VA. Of course this value will be slightly different due to losses but this is a general figure.
My local electronics supplier has a variac that is rated for 500VA, therefore with a 50VA surplus. So, is the ~450VA output from the NST really going to be that value or will it fluctuate? If so, what would cause this? And should I get the variac at the local supplier?
I have a 500VA variac, and I suspect it may be the same one. Red 240V 2A unit with a front voltmeter, sold by Jaycar (or similar supplier to Aus and New Zealand)?
They are very good variacs, and if you change the fuse they can supply a bit more than 2 amps for short periods. In regard to your 450VA NST, is it labelled for 120V or 230/240V input? At if it's a 230V NST it will draw around 1.9A, but if it has a 120V primary it will draw roughly 3.75A, which will be quite hard on the little variac, but if you limit run time to a few minutes and swap the 2A fuse for a larger one, then it shouldn't overheat. There will be increased wear on the brush however.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
I have a great HowTo on spark gap coils on our website under the Resources section. "How I design my Tesla Coils." It takes a budget approach to selecting materials and spec'ing out a tesla coil.
Registered Member #3395
Joined: Thu Nov 04 2010, 08:42AM
Location: Christchurch, New Zealand
Posts: 193
XravenorX wrote ...
Jozef C wrote ...
What about a variac that would be suitable (i.e: the correct power rating) for using this TC? I will be using a 15kV 30mA NST to power the primary so I calculated that 15kV @ 30mA = 450VA. Of course this value will be slightly different due to losses but this is a general figure.
My local electronics supplier has a variac that is rated for 500VA, therefore with a 50VA surplus. So, is the ~450VA output from the NST really going to be that value or will it fluctuate? If so, what would cause this? And should I get the variac at the local supplier?
I have a 500VA variac, and I suspect it may be the same one. Red 240V 2A unit with a front voltmeter, sold by Jaycar (or similar supplier to Aus and New Zealand)?
They are very good variacs, and if you change the fuse they can supply a bit more than 2 amps for short periods. In regard to your 450VA NST, is it labelled for 120V or 230/240V input? At if it's a 230V NST it will draw around 1.9A, but if it has a 120V primary it will draw roughly 3.75A, which will be quite hard on the little variac, but if you limit run time to a few minutes and swap the 2A fuse for a larger one, then it shouldn't overheat. There will be increased wear on the brush however.
Thanks ravenor, yes it's the exact variac and it's a 230v input. Sounds good so I shall buy it. In the worst case scenario anyway, I could always get a slightly higher rated fuse. It's not like I'm going to run this TC for hours anyway
Registered Member #3395
Joined: Thu Nov 04 2010, 08:42AM
Location: Christchurch, New Zealand
Posts: 193
EasternVoltageResearch wrote ...
I have a great HowTo on spark gap coils on our website under the Resources section. "How I design my Tesla Coils." It takes a budget approach to selecting materials and spec'ing out a tesla coil.
Page here:
Wow, thanks a ton for the link! This is really helpful and it gives a good backbone to the design and construction process. I'll have a more in depth look at it soon
Registered Member #3395
Joined: Thu Nov 04 2010, 08:42AM
Location: Christchurch, New Zealand
Posts: 193
Somebody who made an SGTC told me that one time when he was operating his TC, it's interference screwed up his laptop. I know that TCs cause a lot of EM interference with electronic devices, so how can I minimise that risk by containing the EM interference?
I think one of the attributing problems in my circumstance is that I live in a relatively dense neighborhood so all the houses are very close together and one the last things I would want to do is bugger someone's laptop.
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Help needed - 1st SG Tesla coil
