Want a temperature-controlled cordless soldering iron? You can’t buy one, but you can build a DIY one for tinkering in the field: Good soldering requires good tools. In particular, a soldering iron that uses feedback to keep the tip at a set temperature works much better than one that doesn’t. That functionality is easy to find in a bench soldering station, but try to find a cordless iron with it, and you’ll be out of luck. This DIY solution solves that problem by marrying the business end of a Weller “Magnastat” soldering iron with a Maglite flashlight.