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Grounding my NST?

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weezilla

Wed Feb 06 2008, 08:02PM

Registered Member #1296 Joined: Wed Feb 06 2008, 07:28PM
Location:
Posts: 3

Hello ! I am a college student looking to build my first tesla coil. I don't have much experience with electronics (I've read a little), but I am very careful. Anyways, I just got my first transformer in the mail today, and I was looking to build a simple jacob's ladder today to test it out.

To the point, I want to be sure I have everything set up safely before I operate. I will be going to Lowes to buy two insulated wires to plug into a 120v outlet in my room, and maybe a kill switch for the input (Does the kill switch need to be connected to only one wire going in the primary, or both?). I just need to know where to ground it from? I have a "secondary mid-point ground" on my NST. It is a 15000v 30mA.

Anyways, What gauge/type of wire do I use, and should I run it outside my window into the earth with a metal stake or something? I live in a dorm, and there's not really anywhere to ground it other than the dirt.

Your advice is greatly appreciated !

Nik

Wed Feb 06 2008, 08:11PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

For an NST you will need some 12 or 14 awg 2 conductor (+ground) "cord wire" (the orange stuff that extention cords are made of) and a plug end. You can get that stuff at any hardware store. The ground on the NST (secondary midpoint) goes to the regular ground of the building. If you need to learn how to attach the cord end (bit with prongs) onto the cord you can google that yourself.

weezilla

Wed Feb 06 2008, 08:17PM

Registered Member #1296 Joined: Wed Feb 06 2008, 07:28PM
Location:
Posts: 3

Thank you so much for the reply =)

From the reading I've done, whenever I hear somebody talk about grounding, they say to not run it into your "main" ground. I assumed that meant into the ground of your house. Could you elaborate slightly?

Billybobjoe

Wed Feb 06 2008, 08:45PM

Registered Member #396 Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176

Are you sure you weren't reading about tesla coils? An NST is fine to connect to ordinary mains ground - they are designed that way.

teslacoolguy

Wed Feb 06 2008, 10:29PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

go ahead and connect it to the house ground in fact i have operated mid point grounded nst's without any ground connection at all and it worked just fine just be sure not to touch the nst while it is on but i do recommend grounding it but it is not absolutely necessary

ArcLight

Wed Feb 06 2008, 11:20PM

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

weezilla,

You seem to be a little unsure about wiring. Given your situation, this is what I would do. Go to Lowes and buy the following:

1. One 3-wire extension cord (whatever they have that's cheap, usually orange in color and 16ga. wire, you can buy heavier wire if you wish, but we're only talking about 450 watts)
2. One SPST light switch
3. One metal utility box
4. One light switch cover for utility box
5. Two wire clamps (the smallest they have, I think 3/8 inch) for utility box
6. One small bag of yellow (or larger orange) wire nuts (you only need two)
7. (Optional) Crimp-on or twist-on eyelets of appropriate size for the lugs on your NST

I suggested an extension cord because it's cheaper than a separate length of wire and plug. Plus, it's pre-wired so we know that the hot wire (the black one) should be attached to the appropriate plug.

Cut the female end off of the extension cord and throw away. Cut off a 3 or 4" piece of the cord and put to one side for use in just a minute. On the extension cord cut back the outside plastic about 3" and strip wires the appropriate amount needed to install the eyelets or attach directly to NST lugs.

Cut the extension cord in two wherever appropriate for distance between wall/switch/NST. Cut back outside plastic and strip wires like before.

Punch out two of the small knock-outs in the utility box (I usually pick one top and one bottom, do whatever works for you.)

Install cable clamps in holes in utility box.

Put the cord to the plug in one clamp and the cord to the NST in other and tighten clamps.

Place one black wire to one terminal of switch (doesn't matter which one) and the other black wire to the other terminal. Then pull the green wire out of that piece of cord the you cut off earlier, strip both ends and attach it to the grounding lug (green screw) of switch.

Twist the three green wires together and the two white wires together and screw a wirenut on each.

Attach switch to utility box cover (you may have to break off some tabs on the switch to make it fit, the switch has been pre-scored for this) and attach cover to box.

You're now ready to run your ladder. If you ever build a Tesla coil come on back and we'll talk about that earth ground.

Regards, ArcLight

weezilla

Thu Feb 07 2008, 04:25AM

Registered Member #1296 Joined: Wed Feb 06 2008, 07:28PM
Location:
Posts: 3

Wow, thanks so much.

I went at about 4pmest to go buy what I need for a jacob's ladder. I wired a 12gauge/3 insulated waterproof wire up to the primary and gruond at one end, and a male outlet at the other end (including ground).

I bought some galvanized steal wire (relatively low gauge) for the jacobs ladder part. I have a video I'll be posting after my exam tomorrowish. Anyways, It worked really well and was very easy. Every use, I tested the secondary leads after it's lost power with an led light to make sure its dead.

I'll definitely be getting the supplies for the kill switch soon and wiring it into the middle of the chord.

Is it necessary to check if the secondary is live after the primary is unplugged? If so, I'd like to wire in a circuit that would test it for power/discharge it.

Thanks for all your helps thus far, very appreciated. I will definitely be building the Tesla coil, and I will try to contribute as much as I can here in return for the help.

Shaun

Thu Feb 07 2008, 05:41AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

The transformer cannot hold any kind of charge; if it's not plugged in there's no danger. Perhaps you are confusing it with the tank capacitor, which can hold a high voltage charge for a long time.

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