How to build a Five Foot Tall Jacob's ladder

This classic climbing arc completes any mad scientist's dungeon. Don't touch the electrodes: they're at 12 kV!

MVI_4415.AVI2 MB

MVI_4416.AVI2 MB

MVI_4417.AVI6 MB

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Step 1: Obtain neon sign transformer

Get a neon sign transformer rated for 9 - 12 kV and 30 mA. Make sure it's an old style, heavy coil transformer and not solid-state. The solid-state transformers won't start the arc.

I got a Transco 12 kV 30 mA transformer on Ebay for $35. It didn't have a wall plug, so I wired one on.

pkrouse says: May 22, 2012. 1:41 PM

I was experimenting with helium + jacob's ladders last year. I had an acrylic tube around my ladder's rods, capped at the top, glued to the bottom. I put a schraeder valve and a bleed tube in the bottom (opening in side the tube, naturally) and filled the thing up with helium. It made a *beautiful* violet arc. I ended up putting a rubber glove on the bleeder valve to handle gas expansion from the heat. I assume I had a leak somewhere, because the effect went away after a few days' time.

Also, the rods were brass, and tarnished. I thought the helium would prevent that ,but it didn't. Been meaning to repeat this with stainless steel rods and a better-constructed tube.

goober6 says: Nov 18, 2010. 8:27 PM

i can only find a 5 kv and 30ma transformer is that ok???

pdub77 in reply to goober6Feb 14, 2012. 4:47 PM

This link should help you: http://teravolt.org/jladder.php

dwhole says: Jun 27, 2011. 8:31 PM

I just scored a 12kV and a 15kV transformer from a local neon sign company, for on $5 each! Haven't tested them yet, but the guy was cool, and said I can exchange them if they don't work. Halloween is gonna be sweet. Great instructable, one that I've always wanted to do.

dog digger says: Jan 1, 2011. 8:46 PM

I love it.
I love how it temporarily sends the camera out of focus

tinstructable says: Nov 30, 2010. 8:03 PM

You should try cooling the copper pipes with liquid nitrogen and then spreading them apart. Perhaps you could also get your hands on another NST and wire it in parallel with the current one to get twice the length of sparks!

dataa2 says: Nov 6, 2010. 1:34 PM

anyone have a good online source for suitable neon sign transformers for good prices other than the obvious ebay ?

brady911 says: May 30, 2010. 6:53 PM

is it just me or is it true that it will produce nitrogen gas or something of the sort. and it will fill the enclosement with the gas.

uGo in reply to brady911Oct 18, 2010. 11:47 AM

it makes O3 ( ozone) ;)

Jimmy Proton says: Aug 7, 2010. 8:24 PM

thats so cool, im making one. that is...after i get a transformer...

Ora says: Jun 16, 2008. 10:03 PM

I was thinking about making one of these and having it horizontal instead of vertical. Would this work, or does it need to be vertical in order for the spark to travel along the length of the copper pipes?

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ewilhelm (author) in reply to OraJun 17, 2008. 10:27 AM

It needs to be vertical. The spark heats and ionizes the air, which reduces its resistance. This heated air tends to rise drawing the spark up. You can blow the spark around, but doing so in a consistent manner would be a challenge.

freakshow freak in reply to ewilhelmAug 2, 2010. 11:50 AM

Having air entering top and bottom seems to help the spark rise, making a kind of chimney i suppose.

Ora in reply to ewilhelmJun 17, 2008. 9:56 PM

Okay, thank you very much.

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killerjackalope in reply to ewilhelmJun 17, 2008. 10:54 AM

Maybe a setup using a computer fan, something quite gentle, it would have to reacht the length of the arc rods though, you could use the power supplies case fan as a source of vaguely warm moving air, if it was a little warmer than room temp it would lower the heat gradient needed to make the arcs move, I think, cold air might have a more pronounced effect for a very powerful and slow moving arc...

Ora in reply to killerjackalopeJun 17, 2008. 9:57 PM

Hmm, that might work. If I give it a try I'll be sure to let you know.

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killerjackalope in reply to OraJun 18, 2008. 1:49 AM

It should work ok if you can get the right airflow...

Hightechk in reply to killerjackalopeJun 11, 2011. 8:34 PM

This would be very interesting if done inside a vacuum

sarosh6 says: Apr 3, 2010. 7:18 AM

Im using a similar NST rated 9kV and 30mA for my tesla coil. It was two brown terminals on the side (similar to yours but on the sides). One side has two such terminals and the other side has only one. Which one of these is input and which one is the output? Also, what wires have you used for connecting the mains to the transformer and what wires do I use with the output current? Thanks!

strmrnnr says: Jan 10, 2010. 4:59 PM

I just had a vision while reading this Eric.

I saw a similar ladder but with smaller, more flexible, tubing being used and the tubing was bent into curves and loops, some similar to a helical staircase. The sparks were traveling around the track of the tube in amazing patterns.

Idonet says: Dec 4, 2009. 10:05 PM

Can you tell anything about the circuitry you use to power that thing?

Idonet says: Dec 4, 2009. 10:00 PM

Wow! This looks really impressive.

hamjudo says: Jan 23, 2008. 9:33 PM

My electronic neon sign power supply works just fine in my Jacob's Ladder. It has safety features that aren't present in the old transformers, and it weighs a lot less. It is current limited, so that nothing bad happens when it is accidentally shorted. It has a builtin GFCI. (Note: a GFCI will only protect stupid people that touch one electrode and create a path to ground. It will not protect stupid people who touch both electrodes!) It has no trouble generating a spark. The power supply is rated at 35ma or 10,000 volts. Since it only draws 175watts, it must not be doing both at the same time. I used a marble floor tile as the base. I glued the transformer and a glass block to the base. I connected the wires to the glass block. It is putting quite a few watts into the arc. Most of that becomes heat, so the copper wires get really hot. The arc is even hotter. The GFCI means that this ladder is far more likely to start a fire, than to electrocute someone. It produces very little RF interference, so I assume there must be some filtering in there somewhere.

Prometheus in reply to hamjudoFeb 7, 2008. 1:05 AM

You have a tolerant "soft-coil" setup, but I should add that it would be advisable to increase the heatsinking capacity of any heatsinks (any aluminum blocks/flanges attached to components) by at least 200%, but do not tie them all together, as voltage potentials may exist between them....do not allow an electrically-compatible connection between them unless one is implied in the circuit. Adding a fan would not be unwise.

The arc itself releases not just the imported power creating the spark, but also adds the atomic level to it. Any electrical arc can create temperatures over 9500C, no matter how minute it may seem, it is fire on a level still not entirely understood by the scientific community. A 100mW transformer can create more than 100W of heat output per minute.....work for you on an atomically-driven perpetual-motion machine, or close to it.

The GFCI has only one purpose: To monitor a current difference between hot and neutral. When one exceeds the other by approx 100mA (depending on calibration), the unit trips, assuming what is called a "ground fault", and promptly disconnects both prongs of the plug through a double-pole contact (both sides removed at once) on what is called a "collapsible circuit" (fault = open with a manual close, in most cases), borrowed from bomb-making technology.

If you have a blown hair dryer, saving the cord and GFCI is smart, even in dry conditions. One day, one may save your life by pure accident, noticing you to be the "ground-fault", which is what they aspire to detect in the long run. The GFCI will immediately recognize a short (probably within 100ms) and trip, and may just prevent a fire as well. Any electrocution will likely be more a lesson learned than a trip to ER....Most Americans need this to ensure safety from themselves and their own ignorance.

All a GFCI needs is a disparity of current on one side or the other....and while it may not save you from a painful shock for stupidity, it may still save your life....Worth using as an additional precaution.

hamjudo in reply to PrometheusFeb 7, 2008. 2:56 PM

I wasn't very precise. The GFCI isn't on the input to the power supply, it is on the two 10kV output leads. I believe this is called a "secondary GFCI", because if the high voltage power supply were a simple transformer, the GFCI would be connected to the secondary winding of the transformer. The 110V portion of the circuit is electrically isolated from the 10kV portion except for a single ground connection, a high voltage current ground fault, even if it goes through a person, is unlikely to create a current imbalance in the power cord. You still want a 110V GFCI to protect against ground faults in the mains portion of the circuit. The neon sign power supply barely gets warm, it has more than adequate heat sinking. Neon sign power supplies have to work when installed in badly ventilated metal boxes as part of an exterior sign of a restaurant in the desert.

Prometheus in reply to hamjudoFeb 12, 2008. 12:54 AM

I might have been unclear as well, the GFCI won't see you from the other side of any isolation transformer, such as neon-sign transformers. A "ground-fault circuit interrupter" can only protect you from the mains current. At the least having one on the kit gives someone a quick and safe way to kill power (by hitting the "test" button), without having to fight a plug loose, but this should not be used as an on/off switch. Tripping the safety manually should be done only in emergency or the potential of one. A GFCI on the secondary side is something I haven't heard of, but it would work in the same way. If one does exist on the secondary side, it will definitely see a person as a ground fault because us bags of meat are far more conductive at 10kV that the current would well exceed 100mA.....but for a secondary-side unit, especially in this application, would trip on at least 5mA. I still prefer the old-school heavy-coil transformer as there is less to go wrong, and it has a purist aspect to it. Solid-state power supplies are prone to the EMF created by an arc, where a heavy-coil type inherently absorbs it. The only remaining RFI escapes directly into the air. "It produces very little RF interference, so I assume there must be some filtering in there somewhere." The filtering is not on the power supply, but rather on other things you expected to pick up the interference. Per FCC rules, it is trying to block out unnecessary interference while not creating any of it's own. I'd give the credit to your other electronics rather than to your kit, as you are using it in ways it wasn't designed for. (In any case, got a make/model for your neon power supply? I'd like to get my hands on one too)

_Manni in reply to PrometheusNov 12, 2009. 9:38 AM

To be on the safe side, how powerful should my transformer be? Note that it is a school project and im taking precautions. lol i don't wna kill anyone.

_Manni

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ewilhelm (author) in reply to hamjudoJan 24, 2008. 1:54 PM

Awesome! Can you post a picture?