> Wait, so it uses a continuous range of voltages instead of PWM to control the heating element? Heating is either on or of, but it's on the order of "a few ti

> Wait, so it uses a continuous range of voltages instead of PWM to control the heating element? Heating is either on or of, but it's on the order of "a few times per second". The heating action is connected to a small indicator lamp that lights up when the transformer is pushing power through the iron. You can hear the transformer buzzing briefly every few seconds to keep the tip around the set temperature. Touch the tip to a large thermal mass, and the transformer buzzes continuously. I expect there is a Schmitt trigger or a simple comparator in the control board that is in charge of the heating action. Again, check out the schematics to see how simple it is. > Do tips not have an ideal voltage for efficiently emitting IR? What do you mean by emitting IR? A soldering iron doesn't melt tin by radiative heating. You make physical contact with whatever you are intending to heat. Are you perhaps thinking of Curie point soldering (or inductive heating) [0]? Those employ a much more complex process. My Weller goes by the "make the pointy metal stick reasonably hot" principle. [0] https://www.metcal.com/wp-content/uploads/2021/11/how-it-works-inductive-vs-hand-soldering-systems-whitepaper-by-metcal.pdf https://www.metcal.com/wp-content/uploads/2021/11/how-it-wor...