This disclosure describes, in part, voice-controlled light dimmers that act as voice-controlled endpoints at which users may provide voice commands. These light dimmers include a front panel module coupled to a power module using a hardware interface. The front panel module may receive input from a user indicating commands for controlling appliances, and send communications to the power module using the hardware interface to control the appliances. In some examples, the communications involve encrypted data sent using an inter-integrated circuit (I2C) protocol using the hardware interface to an electrically isolated power module. The power provided to the appliances may be controlled by the power module of the voice-controlled light dimmer.