Jacobs Ladder
DO NOT ATTEMPT TO REPRODUCE ANYTHING IN THIS ARTICLE. DANGER OF DEATH. HIGHLY DANGEROUS PROJECT.
Project of the month: Build a high voltage device that will arc bolts of electrical discharge from one electrode to another. This arc should rise up to the top of the device and dissipate before another generates itself at the bottom!
How will it work:
Something like this: a large heavy duty transformer will create 29 volts of direct current at a high ampage.
This relatively low voltage will be fed to a ZVS switch. A Zero Voltage Switch. A ZVS switch will convert the direct current into a high frequency switching DC voltage more suitable for the next stage. The Flyback Coil.
For the coil we are using a FlyBack transformer; the type found in old CRT television sets. This will take the input voltage and scale it up around 1000 times producing a staggeringly high voltage. Many thousands of volts.
This voltage is fed by cable to two large vertical electrodes. The energy potential between them is sufficiently high that a spark will arc from one electrode to the other.
This will occur at the base of the unit as this is where the electrodes are closest together.
As the spark generates enormous heat the spark will start to rise. As it gets hotter and hotter it will rise and rise pulling the gap necessary to leap larger and larger. As the spark reaches the top of the electrode it disappears off the top. Then the process starts all over again.
My brother and I started by creating the projects base. The main electrodes used were braising rods, which we would later find out were not the best idea. These rods are soft metal, with a relatively low melting point. As it turns out the Jacobs ladder makes everything it touches extremely hot and consequently the rods did some melting when the arc didn’t rise as expected.
The rods were easily bent round in a U shape and bolted to the wooden platform with screws and washers. The wires from the Flyback were terminated with crimped on adaptors and screwed down between the washer and the screw.
Unsure what gap to begin testing with, we left around 3/4 inch as this seemed like a good starting point.
The supplied Flyback transformer had several connectors. A little googling revealed which was the ground and which of the two thick red wires provided the strongest output. Of the two wires, the thicker of the two had a small rubber cup attached to one end. This supposedly connects the Flyback to the CRT tube it was originally designed for. We snipped this off and terminated it with a crimped on spade. The other output was coiled up and the end insulated with heat shrink.
Of the many terminals on the bottom of the Flyback, one had been pre-wired with a grey wire which is the ground cable. This would be attached to one of the electrodes.
All the components were screwed to the wooden base neatly and the wires kept out of each other’s way as best as possible. The electrodes were brought up straight as possible with curved ends to ‘encourage’ the spark to dissipate as it flew off the top.
The power supply was a very old Farnell 24 volt unregulated supply that provides 10amps. The last safety test notice stated 1991, but the old PSU was still working beautifully. The supply actually output 28.8volts unloaded, and as our ZVS demands 12-36 this seemed perfect.
First turning the device on resulted in a arc being generated at the base of the electrodes. The arc did not rise, but a small adjustment to the electrodes gave a great improvement, seeing the arc rise dramatically up the full length of the electrodes.
The Jacobs Ladder ran well for about 3 minutes. There was a sudden cessation with no obvious cause. Adjustments to the primary coil of the Flyback resurrected the device temporarily but I suspect the secondary potted coil of the Flyback has been damaged. Testing the ZVS reveals normal working conditions, so the next step will be to replace the fly back and try and get the JL working again.
Finally, above is a short video of the Flyback rewound with thinner wire, creating a 1 inch arc between two nails.
And below: The moment it died! 🙁
