“Smart” controllers for windows having controllable optical transitions are described. Controllers with multiple features can sense and adapt to local environmental conditions. Controllers described herein can be integrated with a building management system (BMS) to greatly enhance the BMS's effectiveness at managing local environments in a building. The controllers may have one, two, three or more functions such as powering a smart window, determining the percent transmittance, size, and/or temperature of a smart window, providing wireless communication between the controller and a separate communication node, etc.