Thread: Jacobs Ladder

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I'm thinking of building a Jacobs Ladder for this years haunt. They're pretty straightforward to make from an electronics point of view but I'm curious if anyone else has built one and can offer any tips?

Thanks!

Originally Posted by OpenTrackRacer

I'm thinking of building a Jacobs Ladder for this years haunt. They're pretty straightforward to make from an electronics point of view but I'm curious if anyone else has built one and can offer any tips?

Thanks!

Mine was built around a 15KV neon sign transformer and 4 ft sections of 1/2" copper pipe for the rods. The rods were fitted into PVC pipe fittings and mounted to the top of the transformer with about 2 inches of space from the rod ends to the transformer. Car spark plug wires and connectors are fine for the high voltage side connections. I ran into two issues with mine that I had to solve. The first issue was to be able to adjust the spacing between the rods so that the arc would start and travel consistently. Second was to block wind from interfering with the arc and more importantly keep hands out of the way.
I built a solid wood base under the transformer and wood sides then placed 1/8" plexiglass panels on the front and back with a small gap at the top and bottom to allow heat to escape. Once your spacing at the top and the spacing at the bottom (spark gap) is set, it should run and restart on it's own.

I have built several of these, very similar to Deathly's method. I picked up some Carlin Model 41000 Oil Igniter Transformers (14KV) on E-bay for under $20.00 each. The nice thing about this transformer is that when it sits flat, the high voltage terminal posts point straight up. I had some scrap 10 gauge copper wire, I bent it so the gap at the terminal end was about 3/8" and tapers up to about 1.5 inches - you do have to play with your gaps to get it right. I cover the wires with 4" clear acrylic tubes (also from Ebay). You definitely want to keep these protected from wandering hands. Great prop for an evil laboratory!

Joe

I built a couple a few years back, and they are pretty simple. As everyone else has pointed out, electrode gap is the biggest problem, along with avoiding spark 'stall out' where it just sits there and fails to fire. A remedy for this is the use of a Gabriel electrode. It consists of a third, small electrode connected to one of the outputs by two 1 Megohm resistors and placed at the central base of the long electrodes. This acts as a starter for the spark and insures consistency. You can find a good description and pictures here: Make a Jacobs ladder.

Here's mine (ignore the music)
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Hey, bradg--your jacobs ladder looks awesome!!
I'd be afraid I'd kill someone if I made one. Possibly myself!

Darn, one of my dads friends worked for a transformer company and sold 15k transformers
and he got fired. The company was called franceformers google it.

Originally Posted by Calloween

Darn, one of my dads friends worked for a transformer company and sold 15k transformers
and he got fired. The company was called franceformers google it.

Check and see if you've got any sign companies around (one's that make/repair neon signs). They usually have several old transformers laying around the shop. I bought four used ones from a local shop at $10 each. I've used the oil ignition type before but they do not put out much current (5milliamps) where as a neon transformer will put out around 30milliamps and a nice fat arc.

Thanks for all the comments. I'm going to start looking around locally for a transformer. They're not light so finding one in town will probably save me some money. My biggest concern has been the cabinet and massive amounts of plexiglass required. I was going to build it out of wood instead with a plexi front and Brad's looks a lot like what I had in mind. I was going to mirror the inside but I think I like it blacked out better so I'm glad I got a chance to see the video.

I'm debating between copper pipe and just using steel rods. Brad, can you tell me what you used?

I'll definitely mock it up first to get the gaps figured out before I permanently mount anything.

This should be a good effect and worth the time, as long as I start now!

I used brass brazing rods, 3/16th I think, they can be found at Home Depot or any hardware store that has brazing/welding supplies. Nice, thin solid rods with excellent conductivity. Usually come in about 3' to 4' length. And yes, I just built a wood cabinet with a plexi front piece, easy too see and maintain.

I finally got my transformer. It's a 15,000 volt neon unit that has screw terminal secondaries under a cover at the top. I found someone local who delivered it for $15! I also found the exact insulator standoffs I was looking for today. They'll allow me to adjust the bottom gap as desired with ease (the nails will be replaced by screws).





I was wondering where to get the wire? I'd rather no deal with spark plug wires but no one I've checked locally so far has high voltage wire. I found places on-line selling 20,000 volt wire (14 gauge) for electric fences but I'd rather not buy 50 feet worth.

One more question about the rods... how long do you think I can get away with using a 15,000 volt transformer? I'd like to make it as tall as possible. Also, would steel or aluminum rods work well or is brass the best bet?

Thanks!!!