Development of Microcontroller Based Digital AC Dimmer for Light Intensity Control

This paper presents the development of an intelligent microcontroller based digital alternating current (AC) dimmer for controlling the ambient light intensity. The domestic AC dimmer that are widely used for controlling the load voltage is based on varying the phase angle of bidirectional triode thyristor (TRIAC) using the time constant value which is manually adjusted using variable resistor or capacitor of gate firing circuit of TRIAC. The AC load connected to these domestic dimmers is isolated using the transformer. The main objective of this work is to implement the digitally isolated forward phase controlled TRIAC based light intensity control from the onsite or at remote location using different topologies that replaces the conventional AC dimmer. The capacitive touch sensor is used for finger touch controlled dimming at the onsite location while the remote dimming is performed using Bluetooth communication interface. To perform onsite dimming, AC input voltage supplied to light source is varied in proportional to the time period elapsed during which the finger is placed over the capacitive touch sensor. In order to facilitate remote dimming, the dimming level signal is supplied from Android based smart phone having the application software for paring connection and data communication with Bluetooth transceiver interfaced with microcontroller.