Today's build is really simple but really cool looking miniature high voltage Jacob's ladder. We assemble "15KV high voltage generator kit", get some basic working principles about Jacob's ladder and maybe some more general tips and tricks.

Heart of the build is cheap 15KV high voltage generator kit, i bought it online for about 1.5.- USD.
Total budget on parts was around 2..3USD :)

You can run it on single 18650 battery but i chose dc jack (At the moment the prices of batteries are too high).

Caution! High voltage can be deadly! This project is not a toy, do not
built his project without prior knowledge of electrical or fire safety. Do not touch or correct output wires while device is powered.

Step 1: Main Components

High voltage generator kit - Aliexpress
Momentary push button - Aliexpress
DC jack - Aliexpress
Ring Crimp Terminals/Connectors - Aliexpress
Pin Screw Terminal - Aliexpress
Scrapped copper wire
Plastic jar lids
some nuts and bolts

Optional:1Megaohm resistors

Step 2: 15KV High Voltage Generator Kit

Assembling this kit is straight forward and simple. Components are marked on PCB, just solder them in their corresponding places. Pay attention to diode polarity, it has band to indicate cathode. It's good to add some thermal paste between transistor and it's heatsink.

In our project we'll replace switch for pin screw terminals, or just solder push button with longer wires so we can mount the button away from PCB.

For this project it's better to have momentary switch instead of latching one, it's safer for Jacob's ladder.

Step 3: Step-up Transformer

Before soldering remove enamel coating from wire tips. I prefer to carefully scrape it off using knife or sandpaper, but you can use flame from lighter or try using hot soldering iron.
Use the schematics to connect transformer to pcb. At the end secure it to pcb using cable-tie from kit.

Original wires for transformer where too short, so let's add longer wires and add extra ring connectors to the output wires (it's easier assemble/replace/modify project later if needed).

Add wires to DC input/power as well, later we'll connect them to input jack or batteries.

If everything is wired correctly you can test it out, you should see high voltage arcing between output wires. Input voltage: DC 3.7V-4.2V

Step 4: Enclosure

Good way to utilize plastic lids is to make enclosures for electronics. The thicker the better. I found 2 lids that slide inside each other perfectly and can be friction fit.
Drill holes using schematics for:
push button
dc jack
output wire connectors

Step 5: Two Vertical Wires - Main Attraction

I soldered ring crimp connectors to the end ow wires. You can alternatively just bend loops using pliers. Using connectors/loops it is easy to attach them using nuts and bolts, later adjustments are easier as well.

Give wires the shape as on schematics. Wires have slight tilt to them, its narrow at the bottom and gets wider at the top. Sometimes it's good to add extra bend at the top to be sure the arc will be terminated.

Step 6: Final Assembly

Time to put everything together.
* Using m3 screws and bolts connect 2 ladder wires and transformer outputs to enclosure.
* Screw down push button to enclosure and connect to transformer PCB.
* Add DC jack and connect it to transformer pcb input.
* Now fit wires and pcb inside the enclosure and it's ready!

Step 7: What Is Jacob's Ladder

* High voltage arc is formed between two wires at the closest point.
* Spark ionizes the air around it which becomes conductive and hot.
* Hot, ionized and conductive air raises.
* Arc follows raising conductive ionized air.
* At some point gap Gets too wide and the arc cannot be sustained any more.
* Whole process starts again from narrowest point and so it goes.

Step 8: Bonus Gabriel Electrode

From bigclivedotcom youtube video i got a good tip how to make ladder more reliable. Just soldered 2 x 1megaohm resistors in series to one of the output ladder wires. It hangs in the air near the narrowest point of two electrodes as shown in the picture.
It helps to jump-start the arc making the whole process more reliable.