Tutorial 2: Two Alternating Blinking LEDs - Geviton

Interesting Facts

Although, LEDs have in recent times become immensely popular it was interesting to find out that LEDs have been around for more that half a century. When LED invented was in 1962 by a 33 year old Nick Holonyak Jr. a General Electric scientist. It is important to understand that led is made up diodes.

Therefore, Light Emitting Diodes (LED) are semiconductor devices. Diode allows current to flow in one direction and does not allow reverse currents. LEDs function as a diode in addition to its ability to emit light. Blinking LEDs is a simple project but, it has a wide range of great applications such as:

Dancing LED circuit used as a visual sign indication in any highway
LED blinking circuit can be used to signal for help
LED blinking can be instrumental as a flashing beacon
Blinking LED can be used as a vehicle indicator

For tutorial 2 we will be blinking led with Arduino from the list provided we have seen the numerous applications of LED applications and now we know why led blinking is important.

Materials Needed

Arduino UNO ( Also Arduino IDE)
LEDs
Resistors 220Ω (led resistor)
Jumper Wires
Breadboard

Connection Procedure

Step 1: Connect the power and ground rails

Step 2: Wire up the first circuit, where the LED anode (the long leg) connected to Pin 4 and the resistor connected to ground rail.

Step 3: Wire up the second circuit, where the LED cathode (the short leg) is connected to short leg to pin 3 and the resistor to 5V rail.

Setup Explanation

The Circuit goes as follows:

In circuit 1 the wire connects from the ground to the 220Ω resistor that is connected to the anode end of the LED to pin 4 of the Arduino.
In circuit 2 the wire connects from the 5V to the 220Ω resistor that is connected to the cathode end of the LED to pin 3 of the Arduino.

The code for the blinking LEDs connected to pins 3 and 4 goes as follows:

The code is an import part of how blinking LEDs work.

Pin 4 circuit (LED circuit 1) that will turn ON using digitalWrite(3, HIGH) on the other hand Pin 3 circuit (LED circuit 2) that will turn OFF using digitalWrite(4, HIGH).

Why? Recall current always flows from a high voltage potential to a low voltage potential.

When Pin 4 is HIGH (5V) therefore, there is voltage difference between Pin 4 and ground thus, current flows from pin 4 to ground. When Pin 3 is HIGH (5V) conversely there is no voltage difference this ensures that no current flows from Pin 3 to 5V.

Code: Blinking Pins 3 and 4