Make: Basic Arduino Projects - 26 Experiments with Microcontrollers and Electronics (2014)

Chapter 9. Multicolor RGB Flasher

Free Running Switcher

In past projects, one or two LEDs, usually red and/or green, were used as visual indicators, letting us know that the Arduino had completed a task or operation. But why limit ourselves to red and green? There is a type of LED that has three different colors all in the same package. An RGB LED has three light-emitting diodes inside of it: one red, one green, and one blue.

In this chapter, you will learn how to use a multicolor LED by building a simple RGB Flasher. The parts you will use for the RGB Flasher are one fixed resistor, a multicolor LED, and an Arduino microcontroller. The RGB Flasher will be built using the handy MakerShield. The Ultimate Microcontroller Pack has all of the project parts you need. Figure 9-1 shows the RGB Flasher block diagram.

Parts List

§ Arduino microcontroller

§ MakerShield kit

§ R1: 330Ω resistor (orange, orange, brown stripes)

§ LED1: multicolor LED

The RGB Flasher block diagram

Figure 9-1. The RGB Flasher block diagram

Circuit Theory

Figure 9-2 shows a typical RGB LED with the wiring pinout names. There are three pins, one for each color, and one common pin for positive attachment to a power supply. Like the ordinary LED, the positive and negative pins are wired to the positive and negative points of a DC (direct current) circuit. To illustrate, Figure 9-3 shows three SPST (single pole, single throw) switches wired to control red, green, and blue LEDs. Closing the contacts on SPST switch SW1 will allow the battery’s (VBattery) current to flow through the red LED, turning it on. The other switches (SW2 and SW3) will turn on the green and blue LEDs as well. The individual colors can be lit sequentially or at random using the three SPST switches. The Arduino microcontroller will provide a sequential switching order, allowing the red, green, and blue LEDs to turn on accordingly.

A typical RGB LED with pinout names

Figure 9-2. A typical RGB LED with pinout names

Three SPST switches controlling an RGB LED

Figure 9-3. Three SPST switches controlling an RGB LED

TECH NOTE

A common anode RGB LED has all of the positive leads connected together to one lead.

The RGB Flasher

The RGB Flasher is an awesome Arduino microcontroller gadget that displays three colors (red, green, and blue) on one LED. You can easily build the circuit on the MakerShield, which will make it portable so you can carry it in your shirt pocket. You can use either the Fritzing diagram shown in Figure 9-4 or the circuit schematic diagram of Figure 9-5 to build the flasher.

The RGB Flasher Fritzing diagram

Figure 9-4. The RGB Flasher Fritzing diagram

The RGB Flasher circuit schematic diagram

Figure 9-5. The RGB Flasher circuit schematic diagram

TECH NOTE

The common anode pin is the longest lead on the RGB LED.

After wiring the components onto the mini breadboard of the MakerShield pictured in Figure 9-6, upload Example 9-1 to the Arduino microcontroller.

The RGB Flasher built on a MakerShield

Figure 9-6. The RGB Flasher built on a MakerShield

Example 9-1. The RGB Flasher sketch

RGB Flasher

Flashes the red, green, and blue LEDs of an RGB LED

Turns on an LED on for one second, then off for one second for each

color LED.

15 Feb 2013

Don Wilcher

// RGB pins wired to the Arduino microcontroller.

// give them names:

int redled = 9;

int grnled = 10;

int bluled = 11;

// the setup routine runs once when you press reset:

void setup() {

// initialize the digital pins as outputs:

pinMode(redled, OUTPUT);

pinMode(grnled, OUTPUT);

pinMode(bluled, OUTPUT);

// turn RGB outputs off:

digitalWrite(redled, HIGH);

digitalWrite(grnled, HIGH);

digitalWrite(bluled, HIGH);

}

// the loop routine runs over and over again forever:

void loop() {

digitalWrite(redled, LOW); // turn the red LED on