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This instructable details the construction of a Jacobs' Ladder display.
If you are not familiar with the Jacob' Ladder, it is a display where an electric arc between two electrodes travels upwards until it reaches the top end of the electrodes, where it extinguishes. The arc then starts again at the bottom, repeating this indefinitely.
I wanted my Jacob's Ladder to be enclosed in a nice looking display case, with any dangerous high voltage points kept out of the reach of anyone.
At this point I have to insert a safety disclaimer.
THIS PROJECT USES HIGH VOLTAGE WHICH CAN ELECTROCUTE YOU.
Make sure that power is disconnected when working on or making adjustments to the unit. Unplug the unit from the wall outlet to be safest. Do not be complacent with safety on this project. Be very careful if you are displaying this to small children or anyone who does not apprectiate the danger.
The construction of a Jacob's Ladder is very straightforward, and there are probably many other plans for this kind of display on this site already. I've detailed my construction in the following steps.
If you are not familiar with the Jacob' Ladder, it is a display where an electric arc between two electrodes travels upwards until it reaches the top end of the electrodes, where it extinguishes. The arc then starts again at the bottom, repeating this indefinitely.
I wanted my Jacob's Ladder to be enclosed in a nice looking display case, with any dangerous high voltage points kept out of the reach of anyone.
At this point I have to insert a safety disclaimer.
THIS PROJECT USES HIGH VOLTAGE WHICH CAN ELECTROCUTE YOU.
Make sure that power is disconnected when working on or making adjustments to the unit. Unplug the unit from the wall outlet to be safest. Do not be complacent with safety on this project. Be very careful if you are displaying this to small children or anyone who does not apprectiate the danger.
The construction of a Jacob's Ladder is very straightforward, and there are probably many other plans for this kind of display on this site already. I've detailed my construction in the following steps.
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Elelectrical Parts List:
*120V power cord. Buy or salvage from an old computer or monitor.
*Receptacle for 120V power cord. I wanted a neat implementation, so I wired the 120V input to a receptacle for the common type of power cords found on computers and monitors.
*Safety Fuse and appropriate fuseholder. I used a common 1 1/4" by 1/4" diameter type fuse and holder. Size the fuse so that it will burn out for currents in excess of the maximum draw from the transformer primary. I used a 5 amp fuse.
*SPST Switch. The switch must be rated to handle more than the maximum current drawn by the primary of the transformer.
*Neon Sign Transformer. The unit I used has a 12 kilovolt secondary output. Transformers will also have a VA rating (volt-amp rating). Divide this number by 120 Volts to get an estimate of the maximum current that will be drawn on the primary side.
The transformer I used is a 360 VA unit, so the maximum current on the 120 volt side will be about 3 Amps.
The best place to find neon sign transformers at a reasonable price is ebay.
*High Voltage Wiring. This is the wiring that leads from the high voltage output terminals of the transformer to the electrodes. I found special high voltage wiring at this web site, Surplus sales of Nebraska:
http://www.surplussales.com/Wire-Cable/HVWire-1.html
The wire I used was the 40kV rated type It is kind of expensive at about $3 per foot, but you only need 2 or 3 feet, so it is worth it. This wire is basically just wire with extra thick insulation.
*Binding Posts . These are used for electrode connection and adjustment. They can be obtained from almost any source that sells electronic components.
*1/8" diameter brass rods for electrodes. The ones I use are for brazing, and can be found where welding supplies are sold. The length will be determined by your specific setup.
Depending on your implementation, some of the items above could be eliminated. For example, you could wire a 120V cord directly to the primary of the transformer without a switch or fuse or removeable socket for the power cord.
Other Parts:
I chose to build a cabinet for my unit. If you choose to construct a cabinet for yours, it will most likely be different from mine, so I won't provide a detailed parts list here. In general, it is constructed from 1/2" and 3/4" plywood for the case, and 1/4" Lexan plastic for the windows. I varnished the wood pieces and added other features like hinged doors and carrying handles.
*120V power cord. Buy or salvage from an old computer or monitor.
*Receptacle for 120V power cord. I wanted a neat implementation, so I wired the 120V input to a receptacle for the common type of power cords found on computers and monitors.
*Safety Fuse and appropriate fuseholder. I used a common 1 1/4" by 1/4" diameter type fuse and holder. Size the fuse so that it will burn out for currents in excess of the maximum draw from the transformer primary. I used a 5 amp fuse.
*SPST Switch. The switch must be rated to handle more than the maximum current drawn by the primary of the transformer.
*Neon Sign Transformer. The unit I used has a 12 kilovolt secondary output. Transformers will also have a VA rating (volt-amp rating). Divide this number by 120 Volts to get an estimate of the maximum current that will be drawn on the primary side.
The transformer I used is a 360 VA unit, so the maximum current on the 120 volt side will be about 3 Amps.
The best place to find neon sign transformers at a reasonable price is ebay.
*High Voltage Wiring. This is the wiring that leads from the high voltage output terminals of the transformer to the electrodes. I found special high voltage wiring at this web site, Surplus sales of Nebraska:
http://www.surplussales.com/Wire-Cable/HVWire-1.html
The wire I used was the 40kV rated type It is kind of expensive at about $3 per foot, but you only need 2 or 3 feet, so it is worth it. This wire is basically just wire with extra thick insulation.
*Binding Posts . These are used for electrode connection and adjustment. They can be obtained from almost any source that sells electronic components.
*1/8" diameter brass rods for electrodes. The ones I use are for brazing, and can be found where welding supplies are sold. The length will be determined by your specific setup.
Depending on your implementation, some of the items above could be eliminated. For example, you could wire a 120V cord directly to the primary of the transformer without a switch or fuse or removeable socket for the power cord.
Other Parts:
I chose to build a cabinet for my unit. If you choose to construct a cabinet for yours, it will most likely be different from mine, so I won't provide a detailed parts list here. In general, it is constructed from 1/2" and 3/4" plywood for the case, and 1/4" Lexan plastic for the windows. I varnished the wood pieces and added other features like hinged doors and carrying handles.
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Your class sounds interesting. Is it a high school or collage type class? Wind turbine tech sounds kind of specific (and unrelated to a jacobs ladder), while electricity sounds more broad and open ended.
I build my unit just for fun. My kids like to see it work.
Good luck with your project!
Thank you for the response and advice. I also used the Surplus sight to purchase high voltage wiring which there are five people in my group and we just split the costs.
Thank you again for your insight and support.
You raise a good safety point that I should add to the instructable. I wouldn't want anyone to start a fire by having the electrodes too close to the top.
On my unit I had to trim the electrodes so that they are about 1.5" down from the inside top to prevent the arc from scorching plywood.
"where can i find very powerful transformers powerful enough to make a 7-12 inch jacobs ladder?"
Don't know if Lexan absorbs UV, but that's a real sneaky danger of the plasma discharge. However, I suspect you're safe as Lexan is an organic polymer- most organics absorb UV.