Introduction: JACOB'S FORKS?

Picture of JACOB'S FORKS?

Check It out in my Art Exhibition:

Well, originally I wanted to make a Jacob's ladder which if you haven't already heard can be extremely dangerous! They are high voltage and if you complete the circuit with your finger it can be fatal...So, be very careful or just don't do it.

Most of the instructions I found used a transformer from a neon sign to generate high voltage and make the thing arc. I didn't want to go out and buy a transformer but I did have an old CRT (Cathode Ray Tube) monitor collecting dust. So, I decided to put it to good use and make a variation of a Jacob's Ladder.


Monitor (CRT)
Wire (12 Gauge?)
Plastic Tube
Materials for Insulation

Step 1: SPLICE

Picture of SPLICE

Open any monitor up, and one of the first things you will see is a big suction cup attached to the CRT. Attached to it is a wire that is at a few thousand volts higher than ground because there is a capacitor somewhere that is still charged up.

The first thing you should do is put on some oven gloves, and get a piece of insulated wire. Attach one end of the wire to a ground pin (look around on the circuit boards etc.) and poke the other end of the wire under the suction cup until you hear a spark noise. Do it a few times until you are SUPER sure everything is discharged, and even then use a multimeter to check the voltages of everything your hands come near.

A flyback transformer in the monitor generates a few kV that is used to accelerate electrons in the CRT to hit the screen. There should be at least two large leads coming out of the transformer. One goes towards the suction cup near the front of the screen (thats the super high voltage one), another goes to the rear end of the tube (should be more or less 0v).

Cut the high voltage wire that goes to the suction cup, splice in a wire of your own and solder.


Picture of INSULATE and GROUND

Be sure to insulate the connection with excellent insulation materials such as paper towels and duct tape. (Just kidding, don't do what I did. Use some non-flammable materials to insulate.) This wire will go to one side of the Jacob's ladder.

Follow the other wire coming out of the flyback transformer, and see where it goes. If there is only one red wire coming out of the transformer like was the case with my monitor you will have to find a another place to solder the ground wire. I soldered my ground wire right where the power cable came into the PCB (Printed Circuit Board).

The ground was obvious in my case but you may have to do a little searching to get it right. If you don't ground the circuit right, the electricity will find its own ground, possibly somewhere else on the PCB and cook the whole monitor so good luck! Use a multimeter...



Like I said before, I originally attempted to build a ladder for the electricity to climb. I couldn't get it to work after a lot of time fiddling with it. I don't know if there just isn't enough voltage produced by a CRT to have it work effectively?

I built the ladder using wood dowels and copper tubing. The spacing of the tubing, the height off of the board, the spread at the top were all touchy and too critical. I could only get the arc to go up about 4 inches and most of the time the arc stayed where the tubing was closest. I was not impressed. After doing a little research online, I found out that:

A Jacob's Ladder works on the principle that the ionized air in the arc is a lower resistance than the air around it and heated air rises. The arc strikes at the point of lowest breakdown voltage - the small gap at the bottom. The heated plasma rises and even when it is an inch or more in width is an easier path for the current to follow. Eventually, the gap becomes too wide, the arc extinguishes and is reestablished at the bottom.

The gap between the electrodes at the bottom of a Jacob's ladder can be critical. Too wide and the arc won't strike, and too narrow and it won't make it all the way to the top. The lower voltage makes the gap even more critical. I found a slight enhancement that is supposed to work. It's simply a third electrode placed between the strike gap at the bottom of the vee. It is connected to either one of the main electrodes via two 1M ohm high voltage resistors.

When an arc should occur, the following happens...The voltage on the middle electrode floats to the potential of the electrode it's connected to via the resistors. It's easy for an arc to jump the short distance from the other electrode to the middle one. When an arc has struck and current is flowing, the voltage on the middle electrode flies up due to the high resistance value. The combination of high voltage at the middle electrode and the ionized path makes the arc strike all the way across.

That all sounded too complicated for the time I wanted to spend so I chose plan B...

Step 4: FORKS

Picture of FORKS

So, I chose the next best thing Jacob's Forks! I found a couple of old forks and attached the ground wire to one fork and the high voltage wire to another fork. I clamped them down and plugged it in. The arc jumped back and forth inbetween the prongs of the fork. It was a far more spectacular light show than the failed ladder.

I then created four circular cut-outs with my whole saw attached to my drill to create insulating plugs. I cut a path through one side of each of the plugs so that I could insert the fork.

Remember not to touch it while its plugged in - or until you have depleted the capacitor by connecting the two contacts until you hear a pop...

Step 5: FOAM and TUBE

Picture of FOAM and TUBE

Next, I attached a 3x3x5 inch block of foam to the top of the back of the CRT casing. I cut out a place for the clear tube that will hold the forks. This is to create a place holder and insulate the monitor from the wires. I then placed a clear plastic tube in the space cut out from the foam. The tube will add some protection from the temptation of wanting to grab both ends of the leads and shock myself to death!


Picture of FORK TEST and FINISH

I connected the lead wires inbetween the plugs to insulate and cut holes in the red caps for the wires. I tested the forks first to make sure it all works before I sealed it off. Looks cool huh?

I sealed off the red caps on the end of the tubes with zip ties and voila! Its done!

(Is anyone enjoying this red carpet?)


Picture of LIGHT SHOW

The electricity arcs back and forth between the tongs of the forks. You could use any number of metal objects to achieve different effects. Just remember to be careful.


hruodger (author)2011-04-27

How do you handle the X Ray emission? As I remember, an open monitor, tv, etc, would emit a little amount of x rays. Even if the cover is made of plastic it shields the radiations. Now that it's open, there could be some of these. MOst of th CRT's have a sticker with a warning.

Ian01 (author)hruodger2017-06-09

AIUI, the X-rays are emitted out the front, if at all. CRTs usually have leaded glass at the front to absorb them and avoid irradiating the user of the computer. In this case, even if the glass is unleaded, the X-rays are aimed at the ground.

R.A.T.M (author)hruodger2011-10-23

yell no the tube gets some power but not enoff becuse hes shorting it b 4 t gets to it

SHOE0007 made it! (author)2016-09-04

I made something similar but with a neon transformer sign. Interesting plasma effect.

CirceWelder (author)2011-12-07

Does the monitor still function? Could it be put back together and used as a pc monitor still with the forks lit? That would be a sick pc mod

BrysonReece (author)2011-07-13

Will this still work if I disconnect the monitor 'tube'? I built this and I LOVE it, but I've been wanting to downsize it to just the PCB, no monitor.

R.A.T.M (author)BrysonReece2011-10-23

yes pull out the pcb clip all the grounds you can cut all of the wire excpt fore ground and hv out be carfel ask if u need any help

dog digger (author)2011-04-16

Not back and fourth. That will only happen if the TV is ancient. If it's newer than 1985-1990 it will be DC. One way

natedawg1013 (author)dog digger2011-06-07

I think he means it sparks between two random close tongs, but keeps switching between them. For example, numbered counter clockwise, like a chip, there might be a spark between tongs 1 and 8 for an instant then maybe 3 and 6 next and so on in a random pattern.

lexvtalionis (author)2009-08-06

So, I've got a sack of high voltage transformers salvaged from CRTs, but the low voltage side has a ton of pins (10-15). Do these transformers normally use 12vdc? 120vac? Will Bad Stuff (TM) happen if I run them at the wrong voltage? These were all free so I think I will just experiment.

BuildIt6000 (author)lexvtalionis2011-01-12

This instructable showed a way to power a flyback transformer: I haven't tried it but it looks like it will work. It also shows how to determine the correct pins to power.

emcelhannon (author)2010-07-24

I've done this a couple o times. I get at least a 1 inch spark for about 2 seconds. Then a relay cuts the monitor off. I've considered bypassing the relay, but I don't want to overload the circuit and lose the driver. And I've tried putting 10w resistors, (2k) on our main line from the flyback. That weajend the arc, but it still cut off. What do guys think is the best solution to this problem?

coolfordy (author)2010-05-31

do older screens have higher voltage flybacks?

Technet93 (author)2010-04-02

Use heat shrink and hot glue.

Turnip123 (author)2009-12-02

Do you mean AND until you have depleted the capacitor?

Mudbud (author)2009-08-09

I really want to make thiis but all I have is the computer monitor curcuit. will it still work if the wires that whent to the monitor are gone?

matstermind (author)Mudbud2009-10-12

mattccc (author)2009-08-30

i did this with a portable crt tv

jschmadeke4life (author)2009-08-21

interesting read! Thank you for taking the time to post this... and yes, we enjoyed the red carpet ;)

DIY Dave (author)2009-08-05

What do you do if you don't hear a spark sound.

noahdsmith (author)2009-07-11

awesome, i thought you might like to know that we tried it to and it looked great.... until the monitor died :-) thanks anyway!

blablabla123 (author)2009-07-01

Nice instructable :). I very much like your art as well, good luck.

Derin (author)2009-06-18

The way you do it,you can play *insert author's fav. game here* while having a light show at the same time!

santy22 (author)2009-06-01

put a wiener between them and see wht happns

welder guy (author)santy222009-06-18

the BBQ of the futuer!!

incorrigible packrat (author)2008-04-13

While it may seem odd to reply to my own reply, I'm taking this opportunity to welcome anyone else reading this thread, to weigh in on the matter. I freely admit to being petty and small-minded, constantly craving affirmation and reinforcement. I am also curious to hear the opinions of third party observers, preferably those with some knowledge of Chemistry (hey Kiteman...)

hey this looks like a fun conversation, to be honest though some of the chemicals may well be produced by electro-weenies they still work as food, hell we drink a good bit of chlorine in drinking water, over time, we accidentally drink pool water... Umm sodium hydroxide can be found in foods and our stomachs make the acids... That and considering the weenie's high resistance not much charge gets to electrolyse the weeny juices... That and you can do worse, like eating micky Ds

Derin (author)killerjackalope2009-05-23

You can also stick LED's into it and have it light up.

Yeah, it's a real joy of a conversation! Curiously enough, I stated most of the stuff that you just did there, but my post was "removed by community request". Strange, I don't recall saying anything overly offensive. I certainly don't recall being consulted on the removal of the comment. Is there a vote on removal of comments? Who is the arbiter of such matters? I mean, I actually did research to make that comment. I spent valuable minutes of time, specially crafting words together in a pleasing fashion, only to have the whole shebang stricken from existence. What's the deal? Mind that I'm not specifically asking just you, killer, I'm addressing anyone who happens to be reading this. (and woe betide anyone whose yen for diversion has struck such new lows as to be reading my own particular brand of inanity...)

btw micky Ds sux! That dang clown Ronald is a mass murderer.

The comments are flagged and a member or staff looks to see if they're appropriate or not, you either said something a little rude or someone thought you were spamming... Odd time I've researched a reply I've gotten stick aswell... Ronald's gonna get drunk, he's going sneak in to ya house, AND RWECK UP THE PLACE!

Funny, if you follow the whole thread, the other feller got rude long before I did. I suppose folks who get all angwy and sulky can go ahead and flag the posts of those who hurt their little feelings, in between their explosions of self-promotion and horn-blowing... (evident if you look for purplish icons elsewhere) But I digress: Ronald's outside distracting everybody, wit' his hands in his big ol' yella pants. Hamburgla's in da house, nickin' everything round and vaguely patty-shaped.

Funny, I thought you a little more mature than that. I have flagged no post since I got on this site, but someone flagged me *actually* defending you for possibly getting flagged. If you were implying that I got rude first, I was not being rude, I was being real. It is you who resorted to insults, thinking you knew the word "remedial" for it's real definition.

Just because you are new to the field of science does not qualify you to imply that I am blowing my own horn. I speak from what I know and that alone. My social experiment on certain other posts has nothing to do with this post. Now you have resorted to incorrigibly immature of you not to maintain tact. Now I have lost all respect for you.

So, calling my ancestry and mental state into question is not considered rude or insulting? How convenient. Please compare your April 10, 6:39 AM post,to my April 10 7:16 PM response, and we'll see who got rude first. Apparently, selective memory also seems to be part of your much-vaunted skill set.

My knowledge or experience with science has very little to do with whether or not you are a hornblower. Your own tootling provides pretty brazen testimony towards establishing that.

As for schooling me on the maintenance of tact, your very first post on this matter is a fairly good example of how not to be tactful. So let's not have any more pot/kettle colour comparisons, shall we.

Respect. I could not give even the tiniest portion of a dook, whether you respect me or not. The tone of your posts indicate that you had no respect for me from the get go, anyhow, so how can you lose something that didn't exist?

Hehe it's funny because it's not a lie, ronald's a rapist and everyone on the internet is a shameless self promotionist I however o it in real life too... Honestly it's quite funny the way that people honestly believe they are the most knowledgable on any subject as well as thinking hat all of the room are below them...

"Ronald beeped up my innards, Pa", quoth young Billy-Joe-Jim-Bob. "And he done made me squeeeaaaal like a pig, too"

And we know how much fun snobs, show-offs and Know-it-Alls are, at real-life parties...

hehe they're a nuisance at parties that's what...

Introduce them to Ronald...

rocksalt2342 (author)2009-04-29

bravo, a great design. probably not a beginner's project though...

The 4th Doctor (author)2009-03-06

And furthermore by the looks of your forks that monitors flyback has a capacitor in it (does it make a buzzing sound while running) so it stores up a charge then pulses. If your flyback didn't have a capacitor you would have a constant arc which would build up heat and rise. as far as I know all monitor flybacks have a capacitor in them therefore monitor flyback jacobs ladder is invalid and forks are boring

Xellers (author)The 4th Doctor2009-04-25

The capacitor in the circuit is the monitor itself, detach the high voltage leads from all of the parts of the monitor (including the suction cup), and it should work fine.

The 4th Doctor (author)2009-03-06

Correct me if I'm wrong but if your using any ground that isent directly on the flyback/before any components after the flyback aren't you risking frying the drive circuitry of the monitor

locofocos (author)2008-05-31

I tried making this, and it works! Or it did. Let me tell the whole story. I went out and got an old CRT monitor for free that was destined for the garbage. I took it apart and it had the suction cup thingy on the back. I tried to discharge it, and there was no zap. So I assumed it was discharged (it was). I then began to cut the wire going to the suction cup thingy and attached a 12 gauge wire to the end going to the transformer. There was another wire coming out of the transformer, but I decided to go with grounding at another spot (probably where I went wrong). I looked on the pcb for something like GND or GRD but couldn't find anything. Near where the power came in, the ground plug (biggest plug, on the bottom) split into two wires. One of the two wires went off somewhere, one went to the metal casing. I decided to attach my ground wire to the metal casing right next to where the ground wire attached to it. Then I put the plastic case back on, running the wires through a hole I made near the back. I bent the wires, already stripped, into a shape where they were pointing towards each other. There was a gap of about an inch. I hooked it up with an extension cord, and sure enough it worked. It wasn't very loud at first. The arc wasn't very bright, and it was kinda red, maybe a little orange. I came back to it after lunch and made a ghetto jacobs ladder out of some bailing wire, duct tape, and styrofoam. This didn't work. It seemed like the electricity was going through the styrofoam, so I shut it off and unhooked it. I put the wires back into their original shape to try it again. The arc was the same color and brightness as it was before for a few seconds. Then it suddenly turned blue and bright like I expected it to be at first. It also started making a rather loud buzzing sound, not like any jacob's ladder I've heard before. I tried moving the wires apart some while it was turned off and turning it back on. It worked, but it started sputtering and then eventually shut off. Now when I turn it on, it just makes a short soft humming noise every few seconds. I tried playing with the gap of the wires and tested the power socket, nothing worked. I'm going outside to try it again to see if it works. I'll reply to this with what I find.

locofocos (author)locofocos2008-05-31

yeah, still getting nothing but a noise every second or so. i think the ground wire may have come loose cause i didn't attach it too well. I'll try opening it up again and see what I can do. if i dont reply again, that means nothing worked and i'm probably gonna go back for another monitor pretty soon :P EDIT: It's broken. I even tried hooking it up right, but I already fried something important. But, I will be going out to get another free one on monday (writing this saturday night). One thing that was odd about mine was that it never held a charge after I unplugged it. When I first got it and tried to discharge it, I didn't get anything from it. Then once I started it up (grounded to the body of the monitor instead of the other transformer lead) and unhooked it, it still didn't hold a charge. But I'll post how the next one turns out.

The 4th Doctor (author)locofocos2009-03-06

bit of a delayed response It probably went arye because using the mains ground probably fried a few things on the monitors control board it didn't happen to this guy so I guess it wont destroy some monitors but it isent a good idea

imthatguy1125 (author)2009-01-20

Hes right this is just plain dangerous

awkrin (author)2008-05-31

this is not something I wanna do! well if I had a workshop, maybe.. this thing is really dangerous. I once tried to put back a computer I just took all the pieces apart, it kinda worked, but I wanted to see if the big cooling block is too hot(from the power supply, which wasn't in it's case) and got shocked, cuz I didn't connected all the ground wires. it was quite pleasant, more like a wave going across my hand, but this thing can kill u

0xCyrusx0 (author)awkrin2009-01-18

Perhaps you shouldn't be taking things apart you know nothing about. Computer power supplies were NOT made to be taken apart by the end user. I've taken many apart however, and usually the heat sinks themselves say 'RISK OF SHOCK- DO NOT TOUCH'

junits15 (author)awkrin2008-12-05

that is bacause the two big capicitors in it were still charged, if you had let the PSU sit for a little while you wouldn't have got shocked.

Inmate1440 (author)awkrin2008-11-06

i had a similar thing happen but a wave not so much more a tsunami of pain and rapid contraction of muscles that i didn't even know i had lucky i just suffered to burns on my fingers and not a heart atttack

topmack (author)2008-10-16

Jacobfork, have you ever seen a 'trick' using a paper towel tube, two pieces of aluminum foil, a 9v battery and some type of RC circuit, that will cause an increasing, building shock if the two pieces of aluminum are connected between the hands?

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