A control system for an electrochromic (EC) device is capable of monitoring the temperature of the EC device without requiring an external temperature monitoring element, and then controlling the EC device based, in part, upon the temperature readings. The control system also provides methods for heating the EC device using current flowing through the device and for simultaneously heating and changing the transmissivity level of the device. The controller also provides security feedback by detecting glass breakage via a high frequency impedance measurement of the EC device. The controller also provides for methods of determining the bleaching/coloring history of the EC device, determining the transmission state of the EC device and applying a holding voltage to maintain the transmission state of the EC device.