Digital Dimmer Circuit – Schematic

The heart of this circuit is the area between the full bridge rectifier and the TRIAC driver. This section of the circuit allows the user to find the zero crossings of the AC signal. The full bridge rectifier creates a fully rectified wave that inputs to an EL817 (photocoupler). This photocoupler sends an input to the Arduino that will trigger an interrupt at the zero crossing. A pulse is generated from the Arduino which is sent to the TRIAC driver which then sends a pulse to the gate of the main TRIAC which allows current to flow through. The potentiometer serves as a means of varying the amount of power sent to the connected load, in this case a blender. Depending on the position of the potentiometer, a proportional delay is implemented before the pulse is sent to the driver which translates to a change in motor speed on the blender.