Introduction: Easy Jacob's Ladder

Picture of Easy Jacob's Ladder

A Jacob's Ladder visualizes electricity by creating a plasma arc that lets you view electricity itself. This project uses exceptionally high voltages and is very dangerous, and should only be done by people confident in what they are doing and who are not working alone.

This Jacob's Ladder is made with two conductive aluminum rulers that have a 12,000V arc continually rising up between them. If that sounds like a lot of voltage, it's because it is a lot.

I know I may be repeating myself, but I cannot stress this enough - this project is dangerous and should not be attempted by anyone who is unsure of what they are doing or working alone! Always make sure someone is nearby while working on this project.

If it sounds like I am trying to scare you, I am. You should have a healthy fear of the amount of electricity that is required to ionize air, and conduct as plasma across an air gap. This is not a toy.

Anyhow, the way the Jacob's Ladder works is that it builds up such a high level of charge it is able to ionize air, and conduct through it from one wire of very high potential to the other wire of much lower potential. When the electricity travels through air, it is basically an electrical short. Thus, not only is it conducting electricity, it is building up a ton of heat. The heat created by arc, begins to heat the air and creates a heated pocket which begins to rise and pushes the arc upwards.

As the arc rises, the distance between the rods increases, and the arc encounters gradually more resistance as the air gap increases. When it begins to reach the top, the resistance of the air becomes too great for electricity to conduct, and the spark breaks. The result of this is that the charge immediately forms again on the bottom (the path of least resistance), and the process starting all over again.

Confused? Learn more about electricity in the Electronics Class.

Step 1: Materials

Picture of Materials

For the Jacob's Ladder you will need:

(x1) 22.5" x 11" x 2.7" shadow box frame
(x1) 12,000V neon transformer
(x1) Right angle power cord
(x2) 12" aluminum rulers
(x2) 1/4-20 x 1-1/2" nylon bolt
(x2) 1/4-20 nylon nuts
(x2) 1/4" x 1" nylon spacers
(x2) 1/4" ring terminals
(x4) 8-32 x 1/2" bolts
(x4) 8-32 nylon insert lock nuts

Step 2: Open the Frame

Picture of Open the Frame

Open your shadow box frame. It must have a glass front. Glass can withstand the temperatures the voltage arc will produce and work as an insulator.

Step 3: Start Measuring the Back

Picture of Start Measuring the Back

To begin with measure 14" from one of the narrowest edges.

Next, draw a line perpendicular to this marking.

Step 4: Find and Mark the Center

Picture of Find and Mark the Center

Find the center point of this line and make a mark.

Make a marking 5/8" to the left and right of the center point.

Step 5: Measure and Mark Another Line

Picture of Measure and Mark Another Line

Next, measure 2-1/2" up from the opposite narrow edge and draw another line.

Step 6: Mark Mounting Holes

Picture of Mark Mounting Holes

Place the high voltage transformer centered upon this line.

Make marks in each of the transformer's mounting holes. Two should land directly upon the line and two should end up between this line and the other line in the center.

Step 7: Drill

Picture of Drill

Drill the transformer's four mounting holes with a 3/16" drill bit. Drill the two holes to the right and and left of the center point with a 1/4" drill bit.

Step 8: Mount the Transformer

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Mount the transformer to the front side of the backing using 8-32 bolts and lock nuts.

Step 9: Trim the Wire

Picture of Trim the Wire

Bring the transformer's output wires to the two center holes, back the wires off about an inch or two and mark the distance on the wires.

Trim the wires at this marking.

Strip about half an inch of insulation off of the ends of the newly shortened wire.

Step 10: Ring Terminals

Picture of Ring Terminals

Slide a 1/4" ring terminals over the ends of the wire and compress their sleeve in place with a crimping tool.

Often a crimp can be found inside the handles of pliers or wire strippers. You likely won't need to get an entirely new tool to do this.

Make sure the ring terminals are firmly attached to the wire by giving them a gentle tug.

Step 11: Attaching the Rulers

Picture of Attaching the Rulers

The rulers will get attached with nylon nuts, bolts, and spacers. Plastic hardware was chosen because it is not conductive.

This is important because it means that there are no high voltage connections found outside of the case. If metal hardware was used, it would be carrying 12,000 volts from the ring terminal, through the bolt, to the nut on the outside of the case. This would highly increase the chances of electric shock. By using the plastic, the high voltage is constrained to the inside of the frame and has no easy pathway out.

Pass a nylon bolt through the top of one of the rulers, and then slide the nylon spacer over its threading. Pass the remainder of the bolt through the frame's backing from front to back, and then fasten it in place with a nylon nut.

Repeat this process for the second ruler.

Once both rulers are fastened tightly in place, position the bottom of the rulers such that they have a small gap of approximately 3/16" between them. They should be arranged so that form a large V-shape with the rulers and are about 3/4" apart at the top.

Step 12: Drill a Plug Hole

Picture of Drill a Plug Hole

Using a spade bit or hole saw, drill a 1-1/8" hole in the bottom corner of the frame on the side that the transformer's plug will ultimately be. This is obviously going to be used to pass the power plug through.

Step 13: Paint the Hole (optional)

Picture of Paint the Hole (optional)

Paint the inside of the hole that was just drilled to match the color of the frame.

This is an optional aesthetic choice.

Step 14: Attach the Plug

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Pass the plug through the hole in the frame and insert it into the transformer.

Step 15: Close It Up

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Insert the backing with all of the hardware attached into the frame, and secure it in place.

Step 16: Fine Tuning It

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Once the case is closed and the frame is set upright, you may plug it in and see if it works.

The arc should start to rise. If it just sits at the bottom, it will start to heat up and melt the metal. Unplug it immediately. The rulers need to be re-positioned.

First things first, whenever you are going to open the frame and work on anything, drape the unplugged end of the power cord over your shoulders. If it is, you will always know that it is not plugged in and it is safe to work on.

Open it back up, slightly tweak the position of the rulers, and then fully reassemble it. It is now safe to plug it back in, and see what happens. If the arc rises to the top and then breaks, then great! You are done. If not, carefully repeat the process of tweaking it until it works.

Step 17: Let 'er Rip

Picture of Let 'er Rip

Once it is working, never leave it running for more than a few minutes as to prevent the excess buildup of heat.

Never leave it unattended.


PaulB535 (author)2017-03-17

What would be a good substitute for the rules? I want more of a mad scientist feel -- would aluminum rods work? any type of metal rod?

randofo (author)PaulB5352017-03-17

Any reasonably thick metal rod should work

GregoryL20 (author)2017-02-07

I used to play with high voltage when I was studying electronics. I made high voltage dc gas laser power supplies using high voltage electrolytic capacitors, high voltage diode voltage ladders, and regulated through high voltage transistors. For transformers I used many types, with the safest being low-potted step down transformers pulled from tvs and monitors (no, not flyback transformers), high voltage transformers I bought from Allied Electronics, starter coils from cars, oil burner transformers, neon sign transformers, and the scariest of them all, high voltage microwave oven transformers. I used a 25,000V neon sign transformer to power a homemade Copper Chloride laser I made from a Scientific American article. I disagree with one person who says "instant death" because it really depends on the capacity of the transformer. For instance, if starter coils were really that dangerous, there would be dead people all over who died from the shock from the spark plug in their lawn mower. But take it from me, seriously, because I once suffered a shock that I thought should have killed me from a discharge of a bank of electrolytic capacitor storing 300uF of 3,000V, ...and I am the son of an electrician, and studied to be an electrician in vocational high have to always know what your body parts are touching, and simply keep all family members, especially children, away from your projects, or you will be very sad for the rest of your life.

AidanF10 (author)GregoryL202017-02-07

you all need to see PhotonicInduction's YouTube channel, then you all will be impressed and think... pfff... just 25k volts....

ovelitsko (author)AidanF102017-02-12

Too bad he hasn't uploaded a video in a while. One of my personal faves is his Mercury arc rectifier. Thing is GORGEOUS!

GregoryL20 (author)AidanF102017-02-08

I would so love to play with lightning.

Nader79 (author)GregoryL202017-02-07

Actually im looking for 2kv@250uf i want 5 i have one, 6 in total, if you have 5 for real good price im willing to buy. Let me know .

Re: Nader

SeanM124 (author)GregoryL202017-02-07

wow, just wow. great job

neondave (author)2017-02-09

I have made one with a 14400v 10kva pole transformer, nice hot arcs. Caution, please

ilpug (author)2017-02-09

Could graphite rods be used to fight heat buildup? I feel like those would have less chance of melting than the aluminum.

Wolf6774 (author)2017-02-09

Good job, but I would rather not spend all my money on an NST, just use a flyback transformer and a driver. Equally dangerous though.

BozoM (author)2017-02-08


ILykMakin (author)2017-02-08

"as to prevent the excess buildup of heat." Would putting a plastic screen in the top and bottom mitigate that since air could be drawn thru?

randofo (author)ILykMakin2017-02-08

I suppose that might work. You would want to be careful on top to make sure it is away from the arc and has a high melting temperature.

ILykMakin (author)2017-02-08

Aesthetic: Paint the inside bottom 1/3 of the glass black to obscure the transformer and point where leads connect to hide the "What is that?" so that people are asking "How does that work?!"

I'd strip the rulers bare too, but that's just personal taste.

randofo (author)ILykMakin2017-02-08

I initially covered it and liked it better with the transformer exposed. You could just flip the rulers backwards also if you don't want to see the marking.

GertF (author)2017-02-08

Wow! Well done. Simple and well thought out. I have always been Interested and admire projects like this. I will, one day, make one when I get over my fear of high voltage.

kbouchard1 (author)GertF2017-02-08

Have never built one, but is cool. If adjusted right, should be able to get it to be like in the movies, where the arc rises, and starts over from the bottom repeating itself over and over. Certainly a smart idea would be to build a plexiglass plastic cylinder as big around as possible. Keep it safer this way. I would however set it up to be that you can adjust the gap to experiment One could drill the ends of the rulers, attach plastic rulers, and have them sit in slots, that you can then adjust the gap to get best effects.

jjon (author)2017-02-07

Great project cool idea. You can also use a Microwave oven transformer commonly called MOT on pages like this. You can just use the coil as is and use two metal hangers as the electroids. Here is a video of the one I made.

josephlebold (author)jjon2017-02-07

I touched microwave capacitors many times lol..

I do always make sure I short their terminals first though.

TonyM251 (author)2017-02-07

Nice Instructable! The only thing missing is a video of it in action.

redlof1 (author)2017-02-07

May a fluorescent light transformer be used instead?

jimmie.c.boswell (author)redlof12017-02-07

probably not using a self saturable reactor fluorescent lamp ballast. it would be very difficult to get an arc start. most fluorescent lamp ballasts are under a 1000 volts.

and there are three main ways to get an arc, high voltage, high current or high frequency. but high current, requires and arc start and is very dangerous. causing flash burns, burns and dangerous high uv radiation, fire danger, blinding, melting electrodes besides the greater electrocution danger.

high voltage low current is better to use. as long as you do not exceed 25 KV, where it would begin to generate significant amount of x-rays and ultraviolet c band. but better to stay within the range of 10 KV to 20 KV and less than 50 Ma.

high frequency, will start and arc at a greater distance for any given voltage or current. but stay well below, infrared and microwave frequencies that will cook you before you become aware of this. and to not interfere, with radio frequencies beginning at 500 KHZ. the diathermy frequency, of below 50 KHZ is a good rule of thumb. and keep the current low, since high frequency burns are very painful and difficult to heal.

GregoryL20 (author)redlof12017-02-07

If you can get your hands on an oil burner transformer, you might try one of those (~10,000 v).

randofo (author)redlof12017-02-07

Typically, not high voltage enough.

qdogg (author)2017-02-07

Be aware that modern gas tube transformers are protected with a device that will no allow them to be used as a Jacob's Ladder. I found out the hard way by getting one at the salvage yard. I had to put in a request at a local sign co. and wait over a month for them to find an outtake from an old sign.

Chuck666 (author)2017-02-07

yes the oil furnace transformer works great. I made a Jacobs ladder for a grandson (Jacob, who could resist) using 1/4 Inch brazing rods for the ladder and an oil burner transformer.

I wrapped a sheet of clear plastic around the ladder to keep breezes from stopping the climb and keep fingers out.

This ruler idea is great.

quietthomas (author)2017-02-07

Shouldn't the ground-fault-interupt (GFI) in that neon light transformer stop this from working?

Sam Grove (author)quietthomas2017-02-07

GFCI devices respond to current imbalances between the primary inputs which indicate that some current is being diverted to ground. They do not protect against shorts in transformer secondaries. That's a job for fuses or temperature sensors.

randofo (author)quietthomas2017-02-07

It doesn't. I believe it is because the air provides resistance so it is not technically shorting (or grounding) the circuit.

GregoryL20 (author)randofo2017-02-07

I agree, it is not really a short circuit, and the ionized air probably has some resistance. Another thought that occurs to me is the possibility of a current limiting high W ballast resistor of some sort, attached directly to one of the metal ruler pieces. But since it works without, probably unnecessary.

dreasen (author)2017-02-07

In the early days of City Museum in Saint Louis, MO we made a Jacobs ladder with a 200 amp panel, a buck/boost transformer and two 8-foot long 1/2inch diameter stainless steel rods. The arc collapsed at around a foot. Yikes! It was expensive to operate though.

randofo (author)dreasen2017-02-07

Oh. That's really cool! I always wanted to go to the City Museum. I drove a car across country last year and tried to convince my uncle (who was with me) to drive a day out of the way to go there, but he wanted to make sure he got home in time for Thanksgiving. Some people and their priorities... :)

Nader79 (author)2017-02-07

I have a 10kv neon transformer will it be ok to use it instead of the 12kv one?

GregoryL20 (author)Nader792017-02-07


randofo (author)Nader792017-02-07

It should theoretically work.

apsteinmetz (author)2017-02-07

Might this work for a temperature limiting auto-shutoff? It's design to turn ON a fan when a space gets too hot but has a "firestat" feature that shuts it off again when the temp is over 183 deg. F. As long as the ON temp is below ambient it should work.

Ventamatic XXFIRESTAT 10-Amp Adjustable Thermostat with Firestat for Power Attic Ventilators

tbirdcw (author)apsteinmetz2017-02-07

Thermostat Temperature Switch 80C 5A Normally closed ???

apsteinmetz (author)apsteinmetz2017-02-07

Never mind. This particular product uses a melting circuit breaker, like a turkey pop-up thermometer. It will work exactly once. I left the comment there because someone else might respond with a better idea.

mmmelroy (author)2017-02-07

Always with making the neat stuff! used to dream of making one of these when i was a kid, but never knew the science to execute. Hopefully some other kid in the next generation doesn't have to dream anymore...

thank the internet for all it offers us.

GregoryL20 (author)2017-02-07

Watching this person making marks on the frame, another interesting version idea comes to me...Has anybody ever tried skipping the metal conductor, and instead using graphite lines drawn on an insulative, high-dielectric surface, such as glass?

guerroloco (author)2017-02-07

The rulers are a nice touch.

random_builder (author)2017-02-06

This is really cool! Please add a video.

gm280 (author)2017-02-05

I have made these with Neon sign transformers and even 555 timer circuits and car coils before. Make absolute positively sure nobody can get into any part of this while on and running. The amount of current the transformers puts out at that high a voltage is instant death. While the are great fun to build and even watch working, it is NOT for a beginner to make one without someone that seriously understands the danger and concept. But nice project all the same.

makendo (author)2017-02-05

Nice. Love these things. A few questions: what were the spacings (top and bottom gaps) that you ended up optimizing to? Might be a good starting point for those who might like to make one. Any difference between steel vs. aluminum rulers (noise?)? Did you consider using a receptacle timer to auto-limit it to a few minutes?

About This Instructable




Bio: My name is Randy and I founded the Instructables Design Studio. I'm also the author of the books 'Simple Bots,' and '62 Projects to ... More »
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