Jacob's Ladder

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Project by jonhodges22 posted 07-31-2009 03:53 AM 2809 views 4 times favorited 17 comments Add to Favorites Watch

This is a Jacob’s Ladder that I built with some oak leftovers from a job. The box is made to just fit the neon sign transformer inside.

Here is a video of it in operation.

17 comments so far

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96 posts in 4281 days

#1 posted 07-31-2009 03:59 AM

Ok now that’s just plain cool. I need one of those to keep my sister’s cat in line.

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13 posts in 4284 days

#2 posted 07-31-2009 04:01 AM

Let’s just hope that cat isn’t curious.

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13 posts in 4284 days

#3 posted 07-31-2009 04:10 AM

It starts on its own. However, if the gap is set too wide then it will not start. Occasionally it will also “go out” after it has been on for a little while, again it is actually because the initial gap is too wide. It can start up in that case but after the copper tubing heats up and the resistance rises it fails to restart. It also works best if the copper is clean, which it isn’t really in the this video.

Answer: —All the wood the woodchuck could get.

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51458 posts in 4536 days

#4 posted 07-31-2009 04:10 AM

Thats pretty neat. Thanks for the cool video.

-- Wayne - Plymouth MN

View Dusty56's profile


11863 posts in 4743 days

#5 posted 07-31-2009 04:14 AM

Well that’s enough excitement for one night for me ! LOL Great job on the box and the device : )
Thanks for the video as well .

-- I'm absolutely positive that I couldn't be more uncertain!

View Mauritius's profile


96 posts in 4281 days

#6 posted 07-31-2009 04:22 AM

Currently the cat is attempting to claw his way to the bottom of an empty cardboard box. Curious does not begin to describe him.

Seriously though, did you have some sort of plans you followed to do this? I vaguely remember reading about this in old school textbooks but it has been quite some time.

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273 posts in 4769 days

#7 posted 07-31-2009 04:32 AM

where did you get the transformer

-- Do something nice for somebody

View jonhodges22's profile


13 posts in 4284 days

#8 posted 07-31-2009 04:36 AM

No plans, it is actually very simple. Although I think there are a number of ways to build one that is more complicated. This one simply uses a, rather large, neon sign transformer. The inputs of the transformer connect to A/C power, just as they would for lighting up a neon sign. On the two outputs you can connect wire or tubing or the like and simply route it close enough to let it create the initial arc. If it is routed too close to the case of the transformer it will arc back to it, but no harm seems to come of that. The heating of the air by the arc causes it to rise and the widening of the gap causes it to eventually break the circuit. The most important thing is to avoid being electrocuted when playing around with something like this. Some neon sign transformers do not have high enough voltage output to do this and I believe some have protection circuitry which prevents it as well. I’ve also seen them made with oil burner ignition transformers and microwave transformers, though the neon sign transformer is probably the simplest and safest.

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13 posts in 4284 days

#9 posted 07-31-2009 04:38 AM

The transformer was an eBay find, I think I won it with a two dollar bid but had to pay about $30 shipping. The transformer weighs about 20 lbs. if I remember correctly.

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593 posts in 5027 days

#10 posted 07-31-2009 04:42 AM

Nice box. How do you access the interior? Does the lid opens?

The electrical part is cool indeed. Although, for those of you seeking to make one, here is a tidbit from the corresponding Wikipedia page:

”Health hazards:

The sparks can burn through thin paper and plastic and start fires; contact with the exposed high voltage can be lethal.

Exposure to an arc-producing device can pose health hazards. In a closed space such as a classroom or home, the continuous arc formation of an open-air Jacob’s Ladder will ionize oxygen and nitrogen, which then reforms into reactive molecules such as ozone and nitric oxide. These free radicals can be damaging to the mucous membranes of people near the spark gap. Plants are also susceptible to ozone poisoning.

These hazards are not present when the arc is formed outdoors since the heated ionized gases will rise up into the air and dissipate into the atmosphere. Spark gaps which only intermittently produce short spark bursts are also minimally hazardous because the volume of ions generated is very small.

Arcs can also produce a broad spectrum of wavelengths spanning the visible light and the invisible ultraviolet and infrared spectrum. Very intense arcs generated by means such as arc welding can produce significant amounts of ultraviolet which is damaging to the retina of the observer. These arcs should only be observed through special dark filters which reduce the arc intensity and shield the observer’s eyes from the ultraviolet rays.”

Not to demerit the project in any way but, if I were you (or your cat!) I’d be very careful…

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13 posts in 4284 days

#11 posted 07-31-2009 04:50 AM

The base is actually screwed on from the bottom with some large countersunk screws, though I haven’t opened it up since I finished it.

And yeah, I should probably edit my project post to carry those warnings because it is serious stuff for all the reasons that wiki entry points out. It is very dangerous and I seldom power it on. So anybody who may now be thinking about making one please make sure you know what you are doing and be careful.

View Mauritius's profile


96 posts in 4281 days

#12 posted 07-31-2009 04:57 AM

Damn, there go my plans for curious cat domination. Thanks for all the info guys, it seems like this may be a better science project than a weekend project!

View bayspt's profile


292 posts in 4760 days

#13 posted 07-31-2009 05:37 AM

Made a small one in high school with a electric fence transformer for Electronics class.

-- Jimmy, Oklahoma "It's a dog-eat-dog world, and I'm wearing milkbone underwear!"

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150 posts in 5000 days

#14 posted 07-31-2009 07:25 AM

Very cool. On my list of things to do now.

Here’s another version:

-- Matt - Syracuse, NY

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10635 posts in 5302 days

#15 posted 07-31-2009 04:48 PM

Very cool project except all the dangers of lasering your eyes blind and entering a different dimension and blasting holes in the sun, very cool. Nice warning though.

-- (You just have to please the man in the Mirror) Mike from Michigan -

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