By Jason Thompson
Updated Aug 30, 2022

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If you’ve ever seen a classic sci‑fi or horror film, you’ve probably seen a Jacob’s Ladder in action. This device generates continuous sparks that travel upward between two metal rods or wires, creating a dramatic lightning‑like effect. It works by generating a high voltage across the rods; when the air between them ionizes, it becomes conductive and a spark leaps from one rod to the other. The heat of the spark causes the surrounding air to rise, so the discharge climbs to the top before fading and restarting at the base.

Step 1

Using a drill, create two holes in the bottom of a wooden box. Space them ¼ inch apart. Then, with a hacksaw, cut a shallow notch—about ½ inch wide and deep—in the top of one side wall to allow the transformer’s power cord to exit.

Step 2

Straighten the coat‑hanger wires. With pliers, smooth out any kinks by gripping the wire just below and just above each bend. Depending on your transformer’s output terminals, you may want to shape one end of each wire into a small hook for easier connection.

Step 3

Connect the coat‑hanger wires to the neon‑sign transformer’s output terminals. Thread the wires through the holes at the bottom of the box so the transformer sits on the floor and the wires extend upward. Position the wires so that they are roughly 3 inches apart at the top.

Step 4

Ensure the transformer’s power cord emerges through the notch you cut. Lay the assembled box on its side, secure the lid, and plug in the transformer to power the device.

Things Needed

• Neon sign transformer
• 2 metal coat‑hanger wires
• Wooden box with lid, slightly larger than the transformer
• Screwdriver
• 4–8 screws
• Drill
• Hacksaw
• 2 pairs of pliers

TL;DR (Too Long; Didn’t Read)

You can use an oil‑burner ignition transformer for this project—its characteristics are similar to a neon sign transformer.

Safety Warning

Never use transformers from microwave ovens; they lack the appropriate characteristics and pose a serious safety risk. Always follow the manufacturer’s safety instructions for your transformer. Do not adjust any electrical components while the device is plugged in. Never touch the sparks produced by the Jacob’s Ladder. Children should use this device only under adult supervision.