1.4 Blinking Breadboard

Most LEDs have a shorter lead and a flattened edge which indicate the cathode.

When we connected our Arduino with the computer we tested the connection by blinking an LED on the Arduino. In this section we will build an external LED circuit for the Arduino to blink. We do not want power running as we build the circuit.

  • Disconnect the USB cable from the arduino in order to remove the power.

LED Driver Circuit

An LED circuit allows electricity to flow through an LED and create light. The Arduino can provide power to the breadboard from the USB cable. We will use a resistor to protect the LED from too much electricity. Take a look at this schematic which shows the circuit.

Power flows from Pin 13 on the Arduino, through the LED and resistor, to ground. It is important to note that electricity can flow through the LED in only one direction. The legs of the LED are called leads. The short lead goes towards ground. We call this lead the Cathode. The long lead, called the anode, goes to power. Many LEDs will also have a flattened edge to indicate the cathode.

  • Connect Pin 13 to one of the numbered rows on the breadboard.
  • Insert the LED into the breadboard with the longer leg in that same row.
  • Insert one side of the resistor into the same row as the shorter leg of the LED.

Now the circuit is set up and ready to run.

  • Reconnect the Arduino to the USB cable.

The blink program we loaded previously blinks the LED on the breadboard. You have your first Arduino project working!

In the next section we will take a look an what is going on in that code we loaded.


There are some videos about these parts in the Discover Electronics Class:
LED Driver Circuit
The Light Emitting DiodeThe Resistor
Solderless Breadboard

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