Young's double-slit experiment is commonly used in undergraduate physics laboratory to show the wave nature of light. As an alternative to expensive commercial kits, here we present an automated, low-cost light intensity measurement setup that allows real-time visualization of the interference pattern. The light intensity is measured by a light dependent resistor placed on the head of a dot matrix printer. The head motion is controlled by an Arduino which also collects the data and send them to a computer. The interference pattern obtained by the setup is in agreement with a model that includes the degree of the coherence of the light source and the effective size related to the light collecting area of the resistor. The apparatus allows quantitative data analysis from the measured light patterns and is suitable to be used in undergraduate physics laboratories.