Jacob’s Ladder


[jandgse812] shows us how to build a Jacob’s Ladder from mostly household parts.   The bulk of the instructions for this project are included in the downloadable document, there is a downloadable video as well. Be sure to follow to the end where he shows us a much safer and possibly better looking revision. The Jacob’s Ladder has become standard fair for any mad scientists laboratory. If you plan on having a workshop suited for world domination, it absolutely must have one of these in it. Be careful though, the high voltage can be deadly.

28 thoughts on “Jacob’s Ladder

  1. I’ve thought about making one from an ignition coil, but I think a neon sign transformer works better. And they usually use some sort of flyback topology with the transformer to make sure the current stays below a certain level. Makes it a little less deadly.

  2. Neon xformers limit current to 30 ma which is not as likely to kill you. Don’t use the kind with a GFCI as they won’t work since the GFCI will trip. They do work wonderfully without the GFCI tho. I had a 30″ tall ladder with a 10″ gap at the top that made an awesome show using a 15kv xformer.

    1. That’s a very dangerous misconception. 30mA at a few kilovolts certainly does qualify as deadly. Many of the neon transformers go up to 25kV (especially when unloaded) and some can deliver even 120mA. That’s anywhere between 40W to 3kW of power! That’s a very serious amount of energy we are talking here.

      How much current you get through your body depends on the skin resistance and insulation. A dry skin has about 100kOhm resistance, so at only 2kV we are already talking 20mA of current passing through your body. If it doesn’t kill you outright, it is going to be an extremely painful and unpleasant experience. At 20kV it is 200mA – that’s guaranteed lethal if the source can deliver at least 100mA of current (many can).

      Even 10mA is enough to kill you if it goes through vital organs – heart or brain (e.g. because you have closed the circuit with your hands). At the very least a shock from one of these will throw you across the room. Then there are secondary problems like high voltage/frequency burns that are difficult to heal and get infected easily.

      Rubber soles, gloves and keeping one hand in your pocket/behind your back (or simply staying away from it!) would go a long way to keep you alive when tinkering with these things.

  3. In my electronics class in high school, our teacher had one he made years before and told us not to get near it. Supposedly, somebody left it on over night and a janitor came in and thought it would be cool to light his cigarette on it but instead got the shit shocked out of him. I don’t know if that is true or not, but it sure is funny.

  4. speaking of mad science, i was amused to see that this page served me an advert for the following:


    “The tesla shield™ emits a positive tachyon field with a radius of approximately 10 meters which is capable of penetrating any material substance or living organism.”

    “the tesla shield™ has the ability to transfer specific information rich energy from the schumann resonance field to the human bioenergetic field. the schumann resonance field is a natural magnetic field with a unique harmonic frequency of 7.83hz.”


  5. Me and my dad made a Jacobs Ladder a few years ago. I wanted it for a Halloween decoration, and when we were eating breakfast in a restaurant, I saw a guy changing the transformers for a big neon sign. After going out to talk to him, he gave us a smaller transformer, I don’t remember the voltage jump, but it was the smaller of two, the larger would shoot a 2″ spark that probably would have maimed me. *__* After some re-bending clothes hangers, we had a 3′ Jacobs ladder. I don’t think it’s been on in a while unfortunately :( It really need a plexi case as to not kill anything.

  6. I did it with a microwave transformer once.

    It produced wicked sparks, but the voltage wasnt high enough for the arc to start if the gap was less than a few milimeters.

    It ended up being “manually operated”, I.e you had to jam a screwdriver in the gap to get each arc going.

    Kind of scary. A one-off novelty project at best but too dangerous to really keep out.

  7. I build one a while ago:

    (Hey, what do you know, that video has sound now. Youtube actually got good codecs).

    It was not as nice as this one – no home made driver circuit, just ripped the circuit directly from an old TV. Dangerous as hell, but the amperage was only 50mA or so, so it wasn’t fatal.

    And before you lament the high pitched speaking, that’s not me, that’s the kid filming it.

  8. You can make a simpler jacobs ladder if you can get the transformer off of a discarded oil furnace burner. The ignition transformer on the old burner puts out 10,000 volts at 20 ma. The newer transformers put out 15,000 volts at 20 hertz and 20 ma I think. The newer one is a solid state power supply, 120v in. The older one is a straight transformer. On the old transformer you can half wave rectify the input and get half wave dc on the output.

  9. @roshamboe: To each his own. But, I prefer to look at this as a proof-of-concept or educational project. There are a lot of hacks that one could consider a “waste of time.”

    I built on of these long ago for a science fair project. It was a project out of Popular Electronics or one of those hobby mags. It used a Quadrac and a couple of other current-limiting things. The assembly minus the rods was enclosed in a metal box with just the terminals sticking out. The project didn’t say anything about not using a two-prong cord, so when you turned it on, you got a nice, healthy shock (and electrical interference) from the corona discharge at the cap of the ignition coil.

  10. I built one of these also with an oil burner transformer. This isn’t the best one I’ve seen but it’s an alright use of the automotive coil. You can make really tiny ones that just sit on your desk with smaller automotive coils.

  11. We built one about 30 years ago with a transformer that had a porcelain standoff marked “65KV” that my friend got from somewhere unknown (we kind of assumed it was a neon sign transformer.) We were too scared to power it with 120 VAC so we used two D-cells hooked in series with a mechanical buzzer. Two bent coat hangers later, and we had a working Jacob’s ladder.

  12. high voltage is fun, and not to be (too much of) a buzzkill, but, guys talking about 30 mA or 50 mA being okay, think again, that can be very dangerous, depending on the path. more than 10 mA can make it so you can’t let go!

    from OSHA on effects of ac electricity:
    * >3 mA- Painful shock- cause indirect accident
    * >10 mA- Muscle contraction – “No Let Go” danger
    * >30 mA- Lung paralysis, usually temporary
    * >50 mA- Ventricular fibrillation, usually fatal
    * 100 mA to 4 A- Certain ventricular fibrillation, fatal
    * Over 4 A- Heart paralysis, severe burn

    always use the one hand behind the back deal, a path through the heart is the real issue — i.e., if you grab the ladder with both hands!

  13. me podria explicar alguien como construir una escalera de jacob con un transformador de microondas me refiero al montaje si puede ser con fotos y en español mejor gracias

  14. Awsome movie loved it! it got leaked.. I watched it a couple days ago online b4 it got out. for those of you who are interested in the site I watched it at here it is: “nowonhd.com” the quality is pretty good..

  15. This movie got leaked.. watched it a couple days ago.. for those of you that are interested on were i saw it at here’s the link: “nowonhd.com” the movie was pretty good i liked it alot.. quality was also great..

  16. When some one said that gfci equip neon transformers dont work, in reality they do. My boyfriend has a 1530bpx120 from allanson, and fired it up 5 ft tall jacobs ladder. Just don’t let the arc hit ground, or it will turn off the transformer. Then you will have to pull the plug to reset it. And or push the bypass button to restart it. He also used the solid state units, and the 9kv to 12kv works the best. If it is a solid state you want to go, get the neon-pro models like the (me-120-12000-30) type of unit also you can try hongba model as well. They will work, but again don’t let any of the arks hit ground. Or you will have to reset the unit. Your best bet is to make sure that you get the right insulators for the job. Do not use any wood, dry or treated of any kind, because high voltage will go through it.

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