I bought a few of these power modules and fly back transformers from Amazon a few months ago, and decided to throw a quick Jacobs Ladder together.
I used a 12 volt power supply and with a few quick wire connections, I was able to produce a spark of an inch or more. That gives me about 12 thousand volts or 1000 times the input voltage.
This power module has a maximum power of 36 volts, so I could probably ramp up the discharge to power a much larger device.
One thing I like doing is sitting back and watching this in the dark.
I use my timer module I made in a previous Instructable, https://www.instructables.com/id/Portable-Shut-off-... and set it for 10 or 20 minutes, and just watch the electrodes.
It makes for a good meditation time, but that's for a future Instructable.
Update: I've made this unit into a machine to make Litchenberg Figures.
See the Instructable at https://www.instructables.com/id/Making-Fractal-Art...
Step 1: Materials
The power module and flyback transformer came in one package. You'll need some two conductor wire for power, or use a flat connector.
They came from Amazon.com.
SainSmart Zero Voltage Switching Tesla Coil Flyback Driver for Sgtc /Marx Generator/jacob's Ladder + Ignition Coil
Step 2: Power Access
I used a Really Useful box for my project.
Using a knife, awl or drill, make a hole for the power wire.
Step 3: Power Connections
The two blue coils on the side of the Flyback Transformer are connected in the middle. Each end will go into one of the three holes on the output side of the module.
The double (soldered) blue wire goes to the middle connection.
The two single blue wires go on either side.
Power is fed in the other end.
Black on the negative, red on the positive.
Ensure you wire the power correctly or you will blow the circuit.
Step 4: Adjust the Gap.
The connections to the hanger wire are with stainless bolts.
3/8" (1cm) gap at the bottom, sloping up in a smooth arc to about 3 inches (9 cm) at the top.
The coat hanger might have a coating so you should remove it. You can use sandpaper, a sanding block, a grinder, or even a file to clean the wire.
I used the bending jig to bend the wire into the nice shape.
Never go near the spark when it's turned in. This could cause serious damage or kill you. Always be in control of the power when it's turned on and don't let anyone near it.
Do not adjust the gap while the power is turned on, and if you've had it on, but have turned it off to adjust it, the wires will get hot so be careful.