How glue gun heating element works?

I've got this little glue gun. On the package it said: 10 watts, AC 120-240V. First of all how is it the same wattage at 120 and 240 volts? I wouldn't think it could be.

Another question. I took it apart expecting to find a coil of nichrome like in a soldering iron. That is not what I found.

Instead I found that the power cord was soldered to two inch long twisty tie wire looking, insulated wires. I dont know what type of wire that would be. It appeared to be brass or copper on the inside coated in what looked like steel though the wire was not magnetic. These two inch long sections of wire had two little paddle contacts on the end and between them was a little rectangular chunk of aluminum. THe contacts and the aluminum chank were wrapped in orange cellophone it looked like. then Sandwiching that were two more flattish rectangular pieces of aluminum. That whole deal was tightly clipped with a steel clip to the alumium housing/nozzle inside of which the glue melts.

My question is-where is the resistor here? Measuring the resistance of the whole glue gun, cold, at the prongs of the plug, the resistance is around 1900 Ohms. I'm seeing some wires hooked to a chunk of aluminum. What am I missing thats creating 1900 Ohms of resistance? It must be that thin cellophane wrapper no? How this type of element works I do not understand. Help?

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nathanaloysiusbash (author) 2 years ago

Hold up, what I thought was a little chunk of aluminum between the paddle contacts, I now don't think is aluminum. Maybe ceramic? It looked shiny but I think that was thermal paste. I measured the resistance, 2500 Ohms. Somewhat approximately the 1900 ohms I was looking for. Do you suppose it's ceramic. Looked kind of like brake pad composite material.

That sounds like a piece of mica insulator. High temperature electrical insulation.

nathanaloysiusbash (author) 2 years ago

I dont know though...It just looks like a little chunk of metal

nathanaloysiusbash (author) 2 years ago

Found out it's a PTC element. See link here: http://dgbizhuo.en.alibaba.com/product/1485338659-...

From wikipedia:

  • PTC Ceramic elements: PTC ceramic material is named for its positive thermal coefficient of resistance (i.e., resistance increases upon heating). Most ceramics have a negative coefficient, whereas most metals have positive values. While metals do become slightly more resistant at higher temperatures, this class of ceramics (often barium titanate and lead titanate composites) has a highly nonlinear thermal response, so that it becomes extremely resistive above a composition-dependent threshold temperature. This behavior causes the material to act as its own thermostat, since current passes when it is cool, and does not when it is hot. Thin films of this material are used in automotive rear-window defrost heaters, and honeycomb-shaped elements are used in more expensive hair dryers and space heaters.

Expensive hair dryers, space heaters, and of course-mini glue guns from the dollar store.

nathanaloysiusbash (author) 2 years ago

I guess I left out the orange cellophane wrapper in the picture. Think a little piece of cellophone big enough to wrap up the paddles with that little chunk of aluminum between them.