The ornamental design for a controller for solderingirons, as shown and described.
FIG. 1 is a perspective view of a controller for soldering irons;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken line showing of the controller for soldering irons is included for the purpose of illustrating portions of the controller for soldering irons and forms no part of the claimed design.