Mini Plasma Pen & Micro Torch

In a previous project (seen here) I modified an arc lighter to cut paper and other thin materials. In this project I've made an alternate design that allows more versatility for both engraving purposes as well as any purpose that might benefit from a small precision torch. This works especially well for wood burning and has a number of advantages over a hot iron in that respect. First, the view of the burn area is not obscured by the tip of an iron. The wood can be seen clearly beneath the arc as it carbonizes to whatever extent is desired. This lack of physical contact also eliminates tool marks that an iron would produce. Perhaps the best feature for this purpose is that using a plasma arc provides complete combustion of any off-gassing from the wood - meaning there is little to no smoke.

The embedded video above details the full process for making this project and written instructions are included in the following steps of this Instructable.

Parts:

• Arc Lighter (can be purchased on ebay for ~$10)
• Brass Brazing Rod (or any stiff brass/copper wire to act as electrodes)
• Scrap Wood
• Multistrand Insulated Copper Wire
• Solder
• Large Insulating Shrink Tube
• Hot Glue

Optional For Torch Modification:

• Thin Brass Tube (approximately 1/8" - 3/16" in diameter)
• Vinyl Tube (matched to fit over brass tube)
• Micro Air Compressor (made for fish tank bubblers)

The first step to this project is to disassemble an arc lighter. Typically that will involve removing a screw from the bottom of the case which will allow the electronics to pull free. Next the pins that hold the top shroud of the lighter in place are pressed out. This should allow the shroud as well as the lid to come off completely revealing the ceramic protector over the electrode wires. The ceramic pulls off easily enough to give full access to the outputs.

With the output wires accessible the electronics are reinstalled in the case. These wires are then extended with some excess copper wire, soldering the joint so they hold firmly. Some heat shrink tubing should be used to insulate these connections. Since this lighter outputs high voltage good insulation is important or the arc may jump between the wires where it's not intended.

Optionally the lid of the lighter can be reinstalled at this point with the output wires passing through. This completes the power supply for this project.

The electrodes are brass brazing wire. I've selected two sections about 3" long and soldered the end of each output wire from the power supply onto each rod. These rods are then held with hot glue to a small scrap of wood that will act as the pen's body. Toward the front, each rod is bent toward the other so they nearly come to a point. This will be the spark gap between the electrodes and can be adjusted for whatever amount of precision is desired.

Plasma is formed when electricity forces a gas (in this case air, primarily nitrogen) to become conductive. The gas molecules and atoms disassociate into a soup of electrons and nuclei which more easily allows the electricity to pass through. These disassociated particles can be manipulated physically by outside forces, such as being blown around by a stream of air which is what will be happening here to turn this pen into a small torch.

A brass tube is glued to the top of the pen and bent downwards at the front to blow air directly at the spark gap. The tube should overhang at the back of the pen so there is room to press on a vinyl tube to attach the air supply. It works quite well to simply blow through this vinyl tube with lung power, but to make things a little more automated I'm using a small air compressor made for a fish tank bubbler.

The final step is to cover as much of the pen as possible in a big piece of shrink tube. Touching the two electrodes could give you a good shock so that's something that's best to avoid. And that's it! The pen/torch is ready to use. Be sure to check out the video embedded on page one to see this project in use.