Before we add a LED to our Arduino we need to learn a bit about resistors since we will need to use one to hook up a LED.

resistors

• Resistors “resist” the flow of electricity (current). The larger the value the greater the resistance.
• Resistance is measured in Ohms.
• Value of a resistor is represented as a series of colored bands.
• Resistor math.
  • Series R_TOTAL = R1+R2 … + RN
  • Parallel 1/R_TOTAL = 1/R1 + 1/R2 … + 1/R_N

Use the following chart to identify the resistors in your Arduino Development Kit:

Image Source: Wikimedia Commons.