Introduction: Mini Jacob's Ladder or High Voltage Climbing Arc

Picture of Mini Jacob's Ladder or High Voltage Climbing Arc

I saw another climbing arc project here and thought: Hey, why not make a tiny one!

Step 1: The Transformer

Picture of The Transformer

First you want to find yourself a good neon sign transformer. It can be anything from 6kv to 20kv. Anything under 6kv and the spark will not spark, anything over, and you could damage the small electrodes. For this project, I used a 9kv @ 30mA made my Allenson. It will run about $10 to $20 on eBay. Or, get one from a dumpster behind a bar.

Step 2: The Base

Picture of The Base

I used an old plactic container with holes drilled in it, and the electrodes hot glued into the holes. As you can see, asthetics were not crucial.

Step 3: The Electrodes

Picture of The Electrodes

You can use pretty much anything here. No more than 16 inches though, remember, we are trying to keep it small. I used a metal coat hanger cun in half. The point at which the electrodes join the base can be any small distance, BUT the electrodes will need to be bentcloser, or else the spark will not start. The basic rule of thumb is about 20kv equals 1 cm of initial gap. As the electrodes go higher, they can be flared out, up to sometimes more than 3 inches.

Step 4: Wiring

If you are unsure of how to wire up a transformer, I'm not really sure this project is for you. But, for those determined enough, I will teach you.
1) Connect the wires to the electrodes (I went up underneath, but you can got to the top of the base) 2) Connect 1 electrode to one output, and the outher electrode to the other output. 3) Connect the 120v mains, making sure that the case is grounded properly.


AlanM65 (author)2016-04-21

"First" should be a discussion about electrical safety. Great tutorial, terrible start and terrible show of concern for those ignorant of the potential for injury or death by making and using this.

EricM20 (author)2015-06-15

I successfully made a Jacobs Ladder using a neon transformer. But when I ran two #12 AWG conductors about 40’ to two terminals so I could reproduce the effect on my outdoor deck, it didn't work.

Was that too far or were the conductors too small?

EricM20 (author)2015-06-11

Chazwhit (author)2007-10-27

Would a gas fernace igniter be any good?

Jimmy Proton (author)Chazwhit2010-08-07


Project_Nightmare (author)2006-12-26

Now all we need is a instructable to do a Ven De Graf Generator and a Tesla Coil to complete the set of high voltage toys :) Good work Resurrecting, I might build one myself

Iv'e got state of the arc info on Van De Graaf Generators & Tesla Coils, plus slightly more modern solid stuff for the Tesla Coils - Both are great (especially the Tesla Coils) for ruining nearby radio & T.V. (I don't know about satellite gear, but nowadays I'm not so much surprised by things as somewhat bemused - no it's not old age - you get like this working with clients that ask you to make daft or just downright weird things for them). So, If you are interested I'll try & dig em out! T.T.F.N. THE LEEWIT. 'It ain't what you do, it's the way that you do it! And that's what gets results!

have you tried a trinary coil on a tesla coil? its just in the process of of making one with a quaternary coil.

since you're making a quaternary coil, i assume that you've already made a trinary coil. if so, please, make an instructable of it. I'd really like to see how that works, and see the specs on it. pics of it in operation would be great, too. not to mention pics of the inner workings of it.

You're in luck, I have a Tesla coil in the works, and a nearly completed VDG. I just need a belt for the Van De Graff.

wtf is a tesla coil

sensoryhouse (author)moobrain2008-02-06

r u can any hobbyist not know what a tesla coil is.........change you name to noobrain

I'm almost finished building my Tesla Coil, so I think I might make an Instructable about it. And probably a couple pics of me zapping myself. :p

if you go to the instructable labled "2nd coil" when you look up tesla coil, in the comments someone posted a site with a cheap tesla coil. also this instrucatble is really lame because you don't explain anything. i read it in 5 mins and if i wasn't as smart as i am i'd not know what i'm doin.

hehe good old high voltage :D not so good if you get on its bad side as my dad found out when hes was "fixing" out exstracter fan :D shot him across the kitchine cus he touched a bare wire the fool i was in the living room pissing my self laphing cus im evil like that >:D

i myslef am working on a tesla coil im gonna make it in the summer but its only gonna be 12inches tall - the base and the torid cuz the 30 inch would cost 1000 bucks this ones gonna cost arond 300 nun the less u will be amazed

knoxarama (author)2009-08-22

dang, i only have a 2kv microwave transformer. can i do anything with that?

spel3o (author)knoxarama2009-12-10

Same here, but those run at an insane 500mA! So a jacob-ladder like ark might be possible...

waldo pollywog (author)2009-09-24

Coat hangars and hot glue will not work for very long as the temp will be way too high. Brass rods purchased at Home Depot will work.Also, these things are potentially deadly even though it's only 30 milliamps.

rginter (author)2009-05-14

That is cool what you did. You can basically take any big device and shrink it down. Please post more.

tyty100 (author)2008-06-27

what if you plugged it right into thje wall???? no transormer would it trip your breaker?

Xellers (author)tyty1002008-11-26

First of all, this operates based upon high VOLTAGE (above a few kV), and not the high CURRENT that the mains provides. If you plugged this in to the mains, nothing would happen. Of course, if you plugged it in and made the electrodes close enough for a small spark, then yes, it would trip your breaker. Do not do this with mains.

livesteamfan (author)2008-11-16

Could I just use a flyback transformer from an old tv or computer monitor?

froggyman (author)2008-10-30

9kw as a minimum lol I made a micro jacob's ladder, it uses 20 volts form a train transformer. It even makes a blue spark that will climb up, its very cool

froggyman (author)froggyman2008-10-30

well i mean it doesnt climb up all that much and well the only thing impressive with it is that it is one of the world' smallest Jacob's Ladder

Chazwhit (author)2007-10-27

If the mains is 230V would that do for a generator built for that voltage?

chriskarr (author)Chazwhit2008-10-06

If the mains is 230V, and you were using a NST rated for 110-120, it would fry the NST.

CameronSS (author)2007-02-11

Could the transformer from a fluorescent tube-type ceiling light work? Even if it only made a spark an inch long, it would still be cool.

thermoelectric (author)CameronSS2008-08-06

They aren't transformers (i think) There just ballasts

Project_Nightmare (author)2007-01-18

Would a jacob's ladder work on DC also? Don't worry, I'm not going to try it.

Yes it would if you could find a diode strong enough to rectify the output of the transforer.

you know, I can't give a definitive answer on that. I would expect that you could do it, but I am willing to give it a try. The easiest (I think) way to test this it to connect a (relatively) low voltage, say 6kv, to a full-wave bridge rectifier made of HV diodes. I don't have any HV diodes, so I will try it with a string of IN4007's and see if they last long enough.

Chazwhit (author)2007-10-27

Would a gas furnace igniter be any good?

chriskim_95 (author)2006-06-28

what about a oil ignitor transformer? Where can I buy one for a cheap price in chantilly VA?

Prometheus (author)chriskim_952007-01-16

oil igniter transfromers are about 2.5kV @ 50mA, so not much good for anything dramatic.

Are you sure about that? I have, among my junk piles, a big jacob's, what I built with a honkin' old oil burner transformer and coat hangers (can't locate it at this very moment or I would relate it's specs) Anyhoo, it starts on a 1/2" gap and will cheerily climb to a 3" and occasionally 4" gap. I can't recall the spark distance to voltage relationship, but a 3" spark requires a fairly substantial voltage. Also, a high current isn't really required here, and could dramatically kill you.

I assume this is a much larger unit than I expect in the typical furnace-igniter. If it can start on a 1/2" gap, it's likely to be about 15kV and a good 25mA to manage 3" in typical humidity. Quite a find, I have to say. For the vague estimate of spark-gap-to-voltage ratio, the approximate is 30kVDC per inch@ 70% humidity. This changes dramatically once a spark has already been formed, such as in a ladder...30kV can travel as far as 4"+ because of the "heated conduit" of the retained spark.

I dunno, the gap may have been closer to 1/4" (still operating from memory here). I think the tranny (is that an acceptable short form for transformer?) had 10000 v stamped upon it. It's also fairly typical of transfor...( wait a sec. a tesla site I used to look at called them OBIT's for Oil Burner Ignition Transformer. How about that for short. Mind you, I've typed considerably more here about possible short forms of the word transformer, than I would just typing transformer in each instance. Perhaps I should investigate macros, but that's another story)... mers that I have seen, from oil furnaces. The furnaces are usually 1960's 70's vintage, back when men were real men, women were real women, and oil burner ignition transformers were possibly more robust (maybe even chock full of pcb's too, but I'm not about to crack one open and find out.) Thanks for the revelation of the spark traveling farther in the "heated conduit" (can we call it a "plasma conduit"?). I suppose this is like one o' them old school light bulbs, wherein the resistance goes down as the filament heats up. Cheers to anyone who reads through all this gas-bagging, and special props to those who locate and appreciate references to Star Trek, Hitchiker's Guide and Hammy Hamster, all in one overly long post.

Project_Nightmare (author)2007-01-18

Forget about my previous question

Prometheus (author)2006-06-17

TV flybacks can be run from a simple oscillator circuit (look into 2N3055's here: ), but flybacks have very low current capabilities.

A microwave transformer is a thought, but only generates a maximum of about 4.1kV, so you have to be very precise to make a ladder from one of those, but it can be done, I have before. They also draw a lot more power than you really need for this, but again, in a pinch they can work. Be sure to keep the capacitor and diode or you will lose half your output voltage. Replacement mixer diodes can be purchased from many appliance shops, and is often the cause of loss-of-power.

The neon-sign trnasformer is the ideal though, and try to get one from a demolition company (some will save things like this on occasion). Getting one that was discarded may be a crapshoot at best, because usually the primary winding is what burns out.

Best way to find the smallest spark gap is to make just a spark gap starting out too wide (start at 2 inches/5cm), and see at what point it will initiate and maintain a spark. If it will maintain a spark as you try to blow it out, you have a good starting measurement. Do not make the gap to small or you can prematurely burn the transformer out.

Never use wood or wood-products as a separator between electrodes as it is not a good dielectric, and can cause fire. Drill a couple holes in a short length of PVC pipe and bolt it down instead. Your local hardware store will surely have bolts and nuts that match for nearly nothing. Fasteners are the least of the challenge...

edeekiss (author)Prometheus2007-01-01

Okay, so in theory, would the spark gap deter microwaves?

Prometheus (author)edeekiss2007-01-16

the transfromer does not make the microwave energy, that is for the magnetron to do (what it's connected to). Without the magnetron, you just have a 4kv power supply.

Project_Nightmare (author)2007-01-02

Great! I can't wait to see the instructables for them! I'd love to see the TC because the instructions on other sites are confusing.

Jlew.blackout (author)2006-10-22

A good Alternative is to use an oil burner furans transformer (it’s a black box above the motor that injects the oil) that has two terminals and just attach the wire in the same fashion just like that. I find it much better/easier to use. (Sorry I don't have any pictures of it) -Jlew

highvotage (author)2006-06-16

you could take the transfomer from a t.v. or a microwave.

andy (author)2006-06-10

wouldnt running it for extended periods of time melt the glue? im not clued up with high voltage stuff but i can imagine a *high* heat output. maybe a warning, just to those unawares, might be in order? might be an idea to clamp the wires between two wooden blocks (screwed together far away from the wires) and put a guard round it, ive had lower voltage wires (50v from a capacitor)send bits of wire flying just some thoughts, if im wrong, please disregard (can you delete comments?) just dont want anyone getting hurt.

_soapy_ (author)andy2006-06-16

No, because the current and therefore power is very low, despite the high voltage. Nearly all the energy is lost into the air. You might get them to wobble a bit if you didn't secure them properly, but they aren't going to "fly across the room".

ll0ll (author)2006-06-13

I really want to make a mini J.L but I dont have and cant find a power supply (in the UK) is ther eanything else I can use or can I use a smaller transformer and make an even smaller j.l ?

I reccomend eBay, but NorthernTool should have some over the internet. If you really are desperate, go to a pub and ask for any broken neon signs. If they won't give them up, nick them from a dumpster.

Eyegor (author)2006-06-13

I made one of these as a kid. You can use wood as a base so long as it's dry, but the potential for an unwanted shock is higher. For that reason, plastic is better. A good way to attach the electrodes is to drill a couple of 1/4" holes and run two bolts with wingnuts and lock washers through them. Then bend a small loop at the bottom of each electrode and pass the bolt through them. Works MUCH better than glueing and it will also hold each wire securely.

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