Basics

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If you are working on a project that responds to sounds, your circuit will require some type of microphone to transduce the sound into a modulated voltage and, most likely, some type of amplification of this modulated voltage. I like to use electret microphones to transduce sound because they require relatively simple circuits. For example,

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The following schematic demonstrates a simple infrared (IR) photodiode circuit using a analog-to-digital converter (ADC) to monitor the photodiode. An analog pin on an Arduino used with the analogRead() function will do the job. Photodiodes are two-pin analog devices. This makes them relatively easy to use and makes their output graded. Some of my students