Resistance is central to traditional soldering irons and to the Cold Heat iron. Electricity moves more easily through substances with lots of free electrons, like copper, than it does through substances with fewer free electrons, like carbon. In other words, substances like carbon have greater resistance. Moving current through substances with high resistance can create heat and sometimes light. This is the same principle that makes light bulbs work -- a light bulb has a resistive filament that gets hot and bright when current flows through it.
The Cold Heat tool's wires
The heart of a Cold Heat tool is a broken circuit that travels from a few AA batteries to a tip that has two halves. The tip can look like one solid piece, but a dark insulating material keeps the two halves electrically isolated from one another.
When you turn the Cold Heat tool on, the switch closes a circuit that also includes a small light. This light lets you know that the tool is on. But a parallel circuit -- the one leading to the tip -- is still broken. This circuit remains broken until you put something conductive, like solder, in contact with both halves of the tip. The solder completes the circuit, also allowing current to pass through a second light.
Because of electrical resistance, both the solder and the tip heat up very quickly, and the solder melts. Dry skin doesn't conduct enough electricity to effectively complete the circuit, so the tip stays cool when you touch it.
Cold Heat Circuitry
We've established that the Cold Heat tool has pretty simple circuitry. The circuit that includes the power switch also includes a small light. A parallel circuit stays broken until both halves of the tip come into contact with a conductive material. A small light on this circuit lights up when it's complete, also.
The Cold Heat tool also has some electronic components beyond basic wiring. A small circuit board is at the end opposite the tip. This circuit board has two diodes, several resistors and a 14-pin integrated circuit. When both halves of the tip come into contact with solder, the chip routes power from the batteries through that branch of the circuit.
So, when you turn the Cold Heat tool on, current flows from the negative pole of the batteries through a wire that leads to a small light. From there, it flows to the circuit board and then to the positive battery terminal. As long as solder isn't in contact with both halves of the tool's tip, that's the end of the process. Once you apply solder, the chip routes lots of power through the portion of the circuit that includes the tip. The electricity moves:
1. From the circuit board to one half of the tip
2. Through that half of the tip
3. Through the solder
4. Through the other half of the tip
5. Back to the circuit board
6. From the circuit board to the positive battery terminal, passing through another small light on the way
The tip
The original marketing materials for the Cold Heat tool described its tip as a patented composite material known as Athalite. We suspect it's made from graphite (a form of carbon) or a substance primarily composed of graphite. Here's why:
* It physically resembles graphite.
* Carbon has 2,500 to 7,500 times the resistance of copper, so it can heat up quickly when exposed to electrical current.
* Some resistance soldering systems use graphite for thicker probes.
* The company has declined to identify the material, but it has said that it's natural and used in blast furnaces and the locomotive industry [Source: Seattle Post-Intelligencer]. Coal, which is mostly carbon, fits that description.
* The Cold Heat tool's patents describe its tip as graphite. The patents also identify the insulator between the tip's halves as mica.
If the tip is really made from a patented compound, another company owns the patent for it. Hyperion Innovations, maker of the Cold Heat tool and owner of the patents describing it, does not own a separate patent for a compound material. In addition, the only patents that list Grigore Axinte -- inventor of the Cold Heat soldering iron -- as the inventor describe tools, not compounds.
from [url]http://.howstuffworks.com[/url]
