High voltage plasma arc!

Thanks to ewilhelm for the original instructable and Prometheus for the tips. This is my version of the Five foot tall jacob's ladder. I changed/replaced some of the parts for better insulation and ease of building.

Step 1: Parts

The main component of a jacob's ladder is some source of high voltage. For this you need to find a neon sign transformer (NST) that has a 8 - 15 kV 30mA output. I got a Franceformer 15 kv 30 mA NST on eBay for $50.

Other things you will need:

2" ABS pipe (30")
2" ABS female T-joint (x2)
2" ABS male adapter (x2)
14 gauge copper wire
.5" acrylic rod (x4 in 6" lengths)
can of expansion foam
hot glue
small rubber bands (x2)

Step 2: Base

First, cut four 4" lengths and one 10" length of ABS pipe. Then drill two holes .5" apart in the middle of the 10" piece to hold the acrylic rods. Put two of the 6" rods into the holes all the way and use hot glue to temporarily hold them in place. To secure and add stability to the rods, fill the 10" piece of pipe with expansion foam. After the foam is dry, cut the ends flush with the pipe and attach the two male adapters. Then attach the four 4" pipes to the T-joints and screw them into the 10" pipe.

Step 3: Transformer

Most transformers don't come with a wall plug, so you'll need to wire on in. Don't worry though, it is really easy. All you have to do is get a wall cord (I got mine at Home Depot) and attach it. Black goes to hot, white goes to neutral, and green goes to ground.
Make sure to ground your transformer!
Once it's wired, attach 18" of the 14 gauge wire to each output and strip the ends.

Step 4: Putting It All Together

Put the copper wires next to the acrylic rods and put the copper pipe over them. You want a snug fit, but might have to cut a small groove into the side of each rod to make it fit.

Step 5: Top Support and Spacing

This will hold the copper pipes at a constant spacing. Take the other two 6" acrylic rods and rubber band them together. Put them near the top of the copper pipes to hold them at the spacing you want. Change the spacing around and see what works best. Always make sure the transformer in unplugged when adjusting anything. Once you find the right spacing, make shallow notches in the acrylic where the pipes should go (see the pic for better explanation).

Step 6: Plug It In!

Make any final adjustments and plug it in!

Safety Tips:

Always unplug before adjusting/touching it
When touching it, still use caution. When touching anything that could possibly have current running through it use the back of your right hand. Electricity makes your muscles contract, and if you touch it with your palm you could get stuck holding onto it.

Step 7: What Not to Do

The first thing I used as a spark gap holder was two CDs. The inside hole fit the copper pipes almost perfectly and the mirrored surface would look cool. I thought CDs were plastic - I forgot that the shiny part is thin metallic foil. It looked cool for a while, but then lit on fire.

Step 8: Final Tips

From a pm from Prometheus

Try raiding any construction site for any neon signs you can find, or try dialing up some demolition companies to see if they have any jobs going for places that might have such neon signs such as bars, supermarkets, or just about any commercial property you can imagine that might have any permanent neon-sign fixture (bars are a sure-fire hit)...Fluorescent fixtures are not worth anything to you for this purpose, so don't even try to seek them out. A parallel-series hookup will just blow them all out as they are only "hi-pot"-ed to 5kV...Neon is the only way to go...

The more archaic the transformer, the better, oddly enough...Older ones were more "overbuilt" for durability with the low-tech methods of the day....Just make sure it works before you invest too much in it though...

You can also try E-Bay, a hobby/salvage shop, or even craigslist.com...In desperation, you can use the transformers for the portable "OPEN" signs when the glass has been broken, don't feel above going that far....I got lucky with my latest haul of three identical heavy-duty neon-sign transformers from a previous demolition nearby....patience might give you the same fortune as well eventually...keep your eyes open...

Assuming you find two or more, never attempt to hook-up the secondary outputs in series with the primary inputs in parallel in an attempt to double the voltage, or you may fry both of them. Don't parallel them either, even if they seem to be identical, as some may have a different impedance than another in the line, and the one with the lesser impedance will work alot harder and possibly fail, and cause the other to fail as well...

If you get really lucky, you might find a 60kV transformer for really large neon signs that still works, and that is a major score.

When making a Jacob's Ladder, *always* start with too-large a gap and narrow it little-by-little....30kVDC jumps about one inch in dry air...AC jumps a little less...Too short a gap and the transformer overheats....run a 'Ladder too long and it overheats...I suggest no more than 5 minutes at a time, with a 20+ minute cool-down afterwards....

If using coat-hangar wire for your electrodes, scrape a line through the coating on the inside (where the spark will travel) for optimal spark performance. Brace wires at the top as the magnetism generated will alter the spark-gap as the spark climbs, resulting in a risky wobble in the electrodes....try folding a drinking straw at the top to brace them and keep them safely separated (DO NOT USE CARDBOARD OR ANY OTHER WOOD-PRODUCT, NON-SILVERIZED/METALLIZED-PLASTICS ONLY!).

Good luck, you will find a neon transformer soon,. just keep your eyes open....and remember, these can kill you, so respect their power as a potential human-cooking-device....

Double....*triple*-check that it is unplugged before you even get near any electrode. Wrapping a miniature neon bulb on either electrode (can be shorted, it'll glow if live and does not need current *through* it to light; just tie it on to either HV electrode to stay put ACROSS THE TERMINALS). Alternately, you can use a miniature fluorescent tube as well (it'll light up if live, will REALLY light up if you touch it when live without delivering a dangerous shock when charged under 30kV....just touch it and you'll see)...

Be safe....check terminals for live with a "backhand" motion, so that if you get shocked, the stronger muscles will pull you away from it instead of making you grab it harder. Grab your wrist with the other hand to resist current going through your heart and causing cardiac-arrest...better through your feet than through your chest...

Good luck...I hope you can find the transformer you need and that you don't get hurt by it....Electricity is a harnessed form of nature....never underestimate it...