Easy Jacob's Ladder




Introduction: Easy Jacob's Ladder

About: My name is Randy and I am a Community Manager in these here parts. In a previous life I had founded and run the Instructables Design Studio (RIP) @ Autodesk's Pier 9 Technology Center. I'm also the author ...

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

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

Please note that some of the links on this page contain Amazon affiliate links. This does not change the price of any of the items for sale. However, I earn a small commission if you click on any of those links and buy anything. I reinvest this money into materials and tools for future projects. If you would like an alternate suggestion for a supplier of any of the parts, please let me know.

Step 2: 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

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

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

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

Step 6: 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

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

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

Step 9: 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

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

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

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)

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

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

Step 15: Close It Up

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

Step 16: Fine Tuning It

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

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.



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    47 Discussions

    Good ! Very aesthetic frame !

    NB : another reason to avoid long run - aside of heat - is ozone production. You should avoid to breath some.

    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?

    4 replies

    Any reasonably thick metal rod should work

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

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

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


    1 year ago

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

    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.


    1 year ago


    "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?

    1 reply

    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.

    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.

    1 reply

    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.


    1 year ago

    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.

    1 reply

    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.


    1 year ago

    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.

    1 reply

    I touched microwave capacitors many times lol..

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