As discussed in Chapter 1, LEDs have a voltage drop of approximately 2 volts across their internal junction, and the voltage can vary depending on the size, color of the LED, and forward current. We will use an analog input on the Arduino and measure the exact value of the voltage drop. Because the microcontroller is digital, the analog information must be converted into the binary system to be processed. In general, when we go from analog to digital we use a device called an analog-to-digital converter (ADC). Going the other way, coming from the digital realm to the analog world, we use a digital-to-analog converter (DAC). For us to measure an analog voltage, as opposed to a logic level, the Arduino ADC will convert the voltage to a binary number between 0 and 1,023.