# Stuck on Tesla Coil

Discussion in 'General Electronics Discussion' started by electricity440, May 10, 2014.

1. ### electricity440

4
0
Apr 6, 2013
(go get coffee to wait for the images to load)
Hi everyone,

For the semester, I have been working on a friend on a tesla coil at a club we started at my high school. We seem to get closer and closer, yet more and more problems come up. We are almost totally out of funds, yet everything seems like it is breaking. |O Here is a bunch of photos on our process, and we would appreciate any help or advice on what to do next.

First, the power supply. We have picked up a bunch of Microwave oven transformers. To be exact, we have 6 of them lying around, and another 2 with dead primaries. We were going to first put four in series to get the minimum voltage needed, 8k, but they arced internally, and we have figured out, two is the limit in series.

Here is the image of two MOTs together, and following is the rest.

With the two MOTS, we realized we would need a voltage doubler, though. We had 5 microwave capacitors, and 4 diodes, and we used 2 of the caps, 2 of the diodes, and another set of 4nf caps to get a 1nf cap across the diode. We used the circuit below:

We tested the circuit, and had great arcs, and they "looked" like high enough voltage for a power supply. Great! Until..... A capacitor popped. Testing it with all of the other capacitors left, the arcs are very small when we make the doubler, and we made sure the capacitors and diodes worked. Here is a few pics of our capacitors and diodes:

High Voltage diodes

1nf Cap bank across the diodes(the blue caps)

Here are the capacitors we have left (we actually might have 3 more microwave capacitors, and 3 diodes at my friends house Note they are all different sizes |O, but all close to 1 microfarad )

Oh yeah, we forgot to put a safety gap if that is important! We made one since:

As shown, we have an electrode for +V,-V,and Gnd from the output of the Doubler.

OK, so on the power supply, what do you suggest? We know we should probably get a NST, but we can't afford one, and for our size of tesla coil, we would atleast need two. (in Parallel)Does anyone know where to get one for a REAlly low price, or maybe someone who would sell one to us for cheap

Next is the Primary Capacitor:

Because we are cheap, we created a capacitor using a bucket, beer bottles, motor oil and salt water as shown in this youtube video:

Here is a photo of ours:

We measured the capacitor, and got somewhere around 15 NanoFarads. We are hoping this capacitor will work for the tesla coil, those Cornell Dubilier caps are pretty expensive!

Rotary Spark Gap
I do not have much pictures for this, we are working on this at my friends house, but I think that will be pretty straight forward, we got 5/32 Tungsten rods, and a 3400RPM pool pump motor, which we will attach using non-conductive plastic from instructions on tb3.com>tesla coil>spark gap We know to put a biggg box around this, because the force will be massive flying around on the motor, and the UV will be bad. I did find this picture, though of the tip of the motor, which we will be attaching the tungsten.

The coil!

The pancake coil on the bottom consists of copper tubing (I think it was quarter inch but it might be bigger). We got 20 feet, thinking that would be enough, but looking at the amount of turns, we may be short. ( I don't know though)

The diameter of the primary coil, which the secondary wraps around is one foot.

The secondary coil

For the secondary, we took a 4 ft by 1ft diameter Sona tubing, and coiled it with fishing line for spacing, and copper wire. We used almost the whole role of 100 ohms of 24AWG wire, which calculated to about 3500 Feet.

Does the primary and secondary coil "work" for resonance, and will this be adequate? We know the secondary is a bit weird just sitting on the base, and we will be able to raise and lower the coil, we have not glued it down

Top of Secondary coil

Toroid

We have a few things laying around for the toroid, will these work?

Thanks for any help, tips, or advice, We really wanted to get this coil done before the end of the school year, but without any help, we are just stuck.

Our work area!

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,480
2,828
Jan 21, 2010
It's very impressive what you've done so far. I have no idea if it's right, or if it's going to work, but I am very impressed that:

1) Your school lets you do this
2) You're not dead

What does your Fraday cage look like? For a Teala coil of this size I expect it's a 5 metre cube?

3. ### electricity440

4
0
Apr 6, 2013
Yeah, We still need to build the cage, as well as a proper grounding, the main rule is stay as far away as possilbe

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