Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

Buy Site Supporter Role (remove some ads) | LPF Donations

Links below open in new window

FrozenGate by Avery

The Jacobs Ladder thread

Tech_Junkie said:
Stupid question, but what is the round red coiled thing? I have a few of these, and never knew what they were for. HV I assume.

pwr_arc.jpg
Click to expand...

That be an inductor. The inductor and capacitor setup resonance in the primary and secondary of the EHT transformer (forming a tank circuit). I am going to add these to my ladder, as it currently produces standard spark as in a spark ignition.

The trick is to tune the oscillator frequency to achieve the resonance.
 
Last edited:





I made a jacobs ladder in a nice plexiglass and wood box with welding rods as the electrodes. Don't have any pictures of it unfortunately, still haven't had a chance to pick up from from school when I showed my teacher! I ran it from a 15kV 25mA NST, which will soon become a CO2 laser power supply :)

Be careful though, when I ran my enclosed (There were a few holes in the top) ladder, it started producing a brown gas, which I later found to be something like nitrogen dioxide or something like that, NOT GOOD!
 
Addonex said:
If anyone here has been to the Fry's Electronics in San Marcos CA. you'll probably have seen the 4 massive ladders they have there. 2 outside and 2 inside both encased in glass (I assume this may support what your professor was saying). Two of these slightly smaller monsters were located right inside the store with many displays/electronics within feet of towers.

I took this picture during a visit a while back of the two outer ones, those 2 blue towers on either side of the entrance:

newhpim1305.jpg


Take a look at the people/cars/door to get an idea of how massive these things are, the arcs inside were easily 2 feet across near the top. Quite a sight to behold :bowdown: Hopefully I'll get some video of them next time they turn them on while I'm there.
Click to expand...

I go to this Fry's all the time! I have see those things run too! Behind each pillar is a door that conceals a pole pig. I saw it once while they were doing some maintenance on them.

I've made three different kids of Jacobs ladders in the past. One form just a NST, another with a automotive ignition coil and a quadrac, and one based off a ZVS driver. ZVS drivers make the best ladders. Because they create the highest voltages at the highest currents with an almost silent spark! My ignition coil ladder is noisy as hell and can't arc very far. NSTs make great ladders but they're very heavy and it can be difficult to get the arc to climb if the voltage is <12kv.

I'll get a video of mine up soon.

-Tony
 
K here is a video of my three Jacob's Ladders. I have them running off my variac because it has a fuse to protect my house mains circuit in case something were to happen. Sorry for the fuzzy pics. I took them with my phone.

IMG_0090.jpg

IMG_0099.jpg


The first one in the video is my automotive ignition coil based driver. The arcs are thinner and usually a fuzzy purple/blue and sometimes orange at the edges. Between the three it probably creates the highest voltage ~20kv but at the lowest current. So the initial gap is largest of the three because of the high voltage, but since the current it low the arc cannot stretch very far and it hardly ever makes it to the top. It's also loud and annoying. It's all dusty because it's been sitting in my garage for years. It's the only nicely constructed one of the three because I made it back in high school and used it for my Senior Exhibition project.

IMG_0092.jpg


The next one is a 12kv 60mA NST driven Jacobs Ladder. It makes some very wide white/orange arcs. It's much less noisy, you only hear a 60Hz hum. It's crudely constructed with copper rod. Since the voltage is much lower the initial gap at the bottom is very tricky to get right. Too close and the arc won't climb, too far and it won't even form. You've only got about 1mm tolerance to get the spacing right. You may notice that the rods start to wiggle after a while. That's because the current in the rods creates opposing magnetic fields which repel and force the rods away from one another. It makes very smooth and consistent arcs and is definitely the easiest to make but it's big and heavy.

IMG_0094.jpg


The last one is my ZVS driver based Jacobs ladder. This one is my favorite. The arcs rival that of the NST and the voltage is much higher too. The gap is not as tricky to set. The arcs are pure white and almost silent. I'm running the driver from 35v dc in this video and it's probably drawing close to 10 amps, so it's a few hundred watts of power. IMO it's not a challenging build but its unforgiving if you make a mistake. I love the efficiency of this circuit. Those big heatsinks are way over kill. The mosfets barely even get warm.

IMG_0095.jpg




-Tony
 
Nice J Ladders!

I found that When I had mine I liked stainless rods better when I used copper they would move. :D

Now look what you guys have started I am going to dig out my NSTs and make one for halloween. :beer:
 
Put a mirror under the ladder and put the laser farther away :na:


Tech_Junkie said:
Nice work. How far was the laser away from the ladder? I'd like to put one right under bottom of the ladder, between the rails where the arc starts. But I've heard electronics and ladders dont mix. I wonder if the laser would survive that close. :thinking:
Click to expand...
 
I'm still torn on which to make. The NST and ZVS are going to be around the same price, because I have to get a power supply for the ZVS. I dont think the coil one will be good for what I want.

I did find out, after hours of searching, that you can use a GFI NST to make a ladder. As long as the arc does not hit ground, it wont trip. You cant use the newer solidstate NSTs with GFI though, because they trigger through sensing the current. You also cant use any GFIs for a Tesla coil.
 
I'm sorry, but what does ZVS stand for? Looks like a CRT flyback design...
NST I've got, but the Z has me stumped.
 
ZVS means Zero Voltage Switching. When the mosfets trigger there is no voltage across them, that's why they stay so cool and the circuit is so efficient. It's also know as a Mazilli Driver, or Current Fed Parallel Resonant CFPR driver.

TJ, I'd say invest in a nice DC power supply or variac rather than just buying an NST. The NST would only be good for a JL or TC or a handful of other HV related projects, but a nice DC power supply can be used for almost anything!

-Tony
 
Last edited:
I saw an old one at the fleemarket for $80. I just dont have the cash. I need to make this thing as cheap as possible.
 
I know what you mean man, I'm right there with you. There are sooo many things on my "want" list right now. But there is only so much I can afford as a poor college student ATM. :undecided:

See if you can track down a couple of used PC power supplies for cheap. 24v dc will get you decent sparks off a ZVS driver, maybe 3-4in arcs.

I'd part with that 12/60 NST if you're interested but since you're across the country shipping won't be cheap unfortunately.

-Tony
 
Hey, hey.

Just scored a 12kv/30ma transformer off ebay for cheap. So the build will progress soon.

I'll post build pix when I finish.
 
From the Avatars I see on this Thread....
All that is missing is Moe...:crackup:

@ T_J.... try not to electrocute yourself...:eg:


Jerry
 
NST's are by far the easiest ways of making a jacobs ladder. I remember 5 or so years ago, I bought an ignition coil jacobs ladder kit. Could never get the arc to actually climb. There is soo little current coming out of the thing it doesn't generate enough heat to make the arc climb.

I put 2 in anti-parallel and I get roughly 70kV, but still barely any current.

You don't really need a variac for a NST. They are transformers, the HV is isolated from the mains. Even if you do hit the mains with HV, the GFI in the house trips instantly (I found out the hard way :p )

I've heard of some solid state NST's working, but nothing beats the old clunky iron and tar bricks ;)
 
You must log in or register to reply here.


Back
Top