Tesla Coil

[Lance]

That’s great. Just don’t expect to get those sized arcs or you will be disappointed.

 

For those still confused about what a tesla coil is look here.

[5614]

in a sense they are fairly complicated, consider they just build up a massive charge and then dischage it everywhere, surely two wires with a massive voltage trying to go through them would make a similar spark?

 

what do people use for their capacitors? proper big ones, or loadsa little ones?

[Lance]

My current bank is 18 1600v .12uf caps in series.

[5614]

and do they all have to have a resistor around them?

[Lance]

If you use a single pulse cap with an NST then no; the cap will drain through the secondary. If you use a MMC then you need a resistor on EVERY capacitor. If you used a single resistor then the overall voltage on all the caps could be 0 but there could still be a charge on individual caps.

[5614]

surely you could take your massive neon sign transformer, plug it in, attach to wires to the output, place them about 20" apart and then a spark should go between them, and if not, place them a bit closer.

 

would that work?

cant see why not and if it does, why do people build tesla coils when they could do that?

[Lance]

The arc will jump about 3/4" but then as the air ionizes and heats up you can drag the arc out about 3"

[5614]

im guessing that you did this [coz of your measurements], how come a tesla coil goes soooo much further than the spark between the wires theory of post #31?

i am assuming that you used the same trasnformer.... or was that the difference? if so what transformer did you use [e.g. its power ratings]

[5614]

what safety precautions are needed for activating and building a tesla coil?

 

except for the obvious, like dont build whilsts the power is on.

dont turn the device on when standing next to it --- how do you turn it on? a switch on a long wire?

do the wires have to be good quality so they dont melt with the high currents?

how close can you stand to an active tesla coil? [medium size, just want a safe approx estimate, i know you cant say for certain]

[Tritium]

The tesla coil will increase your original voltage signifigantly. A neon sign transformer is only 15,000 volts maximum. Im guessing my last tesla coil was outputting anywhere from 750,000 to 1,000,000 volts with about 1000 watts input. This is why the sparks will be significantly larger. The voltage difference tells it all

[Lance]

The frequency also has a large effect. The streamers you are seeing are actually a few thousand sparks on top of each other. The first ionizes the air and then another spark travels through the ionized path and gets a but further and the next spark gets even further and so on.

[5614]

ok, so an improvement on my "tesla coil" aka 2 wires sparking idea would be to have a few neon transformers one after another in series.

 

remember transformers work in ratios, it will keep going up, the input is increased by a ratio, its not like 240 -> 15,000V is a set rate, its just a ratio, put in 120V and you will only get 7,500V output, however there may be a limit to the current the input wire could take, however theoretically, you could attach multiple neon sign transformers in series to kick up the voltage, quite significantly.

 

if 240 -> 15,000

then 15,000 -> 937,500

according to my approx calculations

 

obviously the frequency increase wouldnt be there, but a nice voltage would, assuming that the 2nd transformer could handle a 15,000V input, no reason it couldnt though.

[Lance]

obviously the frequency increase wouldnt be there' date=' but a nice voltage would, assuming that the 2nd transformer could handle a 15,000V input, no reason it couldnt though.[/quote']

 

The primary of a NST is only made for 120v (or 240 in the UK? or is it 220?). The insulation would break down. Not only that but I doubt that the second NST's secondary could withstand that voltage either. A tesla coils secondary only has one layer. In normal transformers the top and bottom of the secondary are right on top of each other.

 

what safety precautions are needed for activating and building a tesla coil?

 

except for the obvious' date=' like dont build whilsts the power is on.

dont turn the device on when standing next to it --- how do you turn it on? a switch on a long wire?

do the wires have to be good quality so they dont melt with the high currents?

how close can you stand to an active tesla coil? [medium size, just want a safe approx estimate, i know you cant say for certain']

 

The only wires you would be near when it’s on are the primary of the NST which is only 120V. There is no danger from just plugging it in. Normal wires could easily withstand the few amps a small NST will draw. The Secondary of the NST (primary of the tesla coil) should probably be made with high voltage wire so you can make everything compact. The current will not be that high on this side.

 

To test the safe distance just makes sure there is a ground rod between you and the coil. That way you can gauge the correct distance in safety.

[5614]

its 240V here in the UK.... so presumably, therefore, either you use a bigger transformer, or we [uK] get a bigger voltage than you [uSA] by the looks of you figure, thats twice a voltage, that makes quite a difference (i would guess from my minor banks of tesla knowledge!!! + the electronics stuff, that helped a bit ]

[5614]

what i meant with the dangers was you somehow have to turn it on, once it's on, if you are still standing next to it, you could be electrocuted, so unless there is quite a big time delay, where is the switch that you turn on located? on a long wire? or do you just turn it on by the mains [plug]

[Lance]

Well there are different versions, yes we do use larger versions. I don’t think you could interchange them. Although if I lived in the UK I would try running two 120v NSTs with the Primary’s in series and the secondary parallel. That way you get twice the current. Although The UK uses 50 Hz instead of 60 Hz here so I'm not sure how that would go over.

[Tritium]

5614 i use a powerstrip plugged into the wall and everything else comes off that. You dont want to have a switch near the coil because there is no delay . I just use the switch on the power strip. I also use a variac to increase the voltage slowly so that i dont have to start at full power. I would recomend this because you dont know what might go wrong.

[Lance]

I also use a power strip which is about 6' away from the coil. I dont use a variac though.

[YT2095]

remote relay switching is also advisable!

[5614]

are tesla coils loud???

 

i was reading this site:

http://www.deepfriedneon.com/tesla_frame1.html

and it said that they are, but no one has ever commented on the sound before.

[Lance]

Oh yes. It depends on your cap bank size though.

[5614]

but why? what makes the noise? ive never heard of a noisy electrical circuit before (except the ones with buzzer/speakers in!)

 

also, if i ran it in the garden, could the sparks set fire to the grass and wooden fence?

[Lance]

but why? what makes the noise? ive never heard of a noisy electrical circuit before (except the ones with buzzer/speakers in!)

 

also' date=' if i ran it in the garden, could the sparks set fire to the grass and wooden fence?[/quote']

 

The spark gap is extremely loud. It’s the same reason lightning is loud. The secondary output is not hot so it presents no fire hazard.

[ultimax]

I'm building my first coil and I need some advice. It's for sch so they're providing most of the components. I'm getting a 15kV 30mA 50hz NST from them (suggested by my prof) and they've given me 30, 1600V 0.047uF capacitors for my MMC.

 

Using WinTesla, the resonant capacitance for this transformer is 0.0064uF. I've read stuff abt how coilers should use a Larger Than Resonant Cap value, 1.5 times that of the resonant. That means the LTR value is 0.0096uF.

 

How should I configure my capacitors? Having 2 parrellel strings of 10 caps in series will give me a capacitance of 0.0094uF. Is this ideal?

 

Also, the leads which came with the capacitors are really short. I need to extend them so that I can solder the caps together. What type of wire should I use? Or will anything be OK?

 

Should I also space the capacitorss a certain distance from each other? Will the leads arc?

 

Thanks!

 

Shu

[SubJunk]

i want one! i'm gonna build a big one like in red alert 2