Deception In Soldering Iron Ratings

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Great Post. Thanks
 
An example:

Pin connections for the desolder gun 8 pole are:
Pin 1 red and pin 2 Grey+yell = element.
Pin 3 blue and pin 5 black = normally open vac switch. (always on for iron)
Pin 4 brown= case ground.
Pin 6 green and pin 7 white = ‘K’ thermocouple.
Wire colors may vary, but this is the info to transpose their 5 pole to 8 pole connectors.

The element would likely have a resistance <100 ohms.
The thermocouple would read a short, BUT it will also read in mV. and vary with temperature. The hotter the tip is, the more voltage.
My tool, you can remove the element and search for the pins with the same resistance.
I have a solder/desolder station also with hot air, but solder and desolder are separate tools.

At a minimum you have a sensor, and a heating element and likely a shield. With de-soldering, you need a switch as well.

Thermocouples are just one way of measuring temperature.
 
wow thank you so much for the breakdown of a solder iron and how it actually works in terms of a wire diagram.

I feel extremely stupid for saying this... but you would touch which two pins of the above described example with your multimeter testing resistance? 3 and 5?

ty so much, really!
 
yes. But in my example 3 and 5 are a switch or permanently on. On a de-solering tool there is a switch, so the resistance would go from infinate to near zero with the switch depressed or not.

Some reverse engineering isn't hard. Usually the element is removeable so you can check the resistance of just the element and "find" the pins where it appears in the cable plug.

The element and shield should be easy to identify.

Then for a soldering iron in my example, two sets of pins would have nearly zero resistance. They would be the always on switch and the thermocouple.

Which one is the thermocouple. The pair that also measures a few mV. Put a match to the tip and they should increase. The thermocouple polarity is a little harder.

A thermocouple is probably the best choice for temperature measurement. To measure temperature, you need the mV reading and the temperature of the terminals at the other end, a lookup table and a reverse lookup table. Solid state sensors and thermisters are typically used to measure the terminal temperature.

If a thermocouple measuring device is shorted with a wire, it will usually read the temperature of the terminals (room temp) or the lowest temperature the instrument can measure. There are different types of thermocouples too.
 
You can also look for a diagram of your specific iron. You may find a complete pinout so you dont have to guess which pins are for what.
 
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