RGB LEDs

RGB LEDs

Three LEDs in One!

• RGB LEDs combine three separate LEDs in one package
  • Red LED
  • Green LED
  • Blue LED
• These primary colors can be controlled separately to create a multitude of color possibilities

Pins

• RGB LEDs have four pins
• Three pins to each of R, G, B (shorter pins)
• One pin serves as either common anode or common cathode (longer pin)

Recall: Current Flow in LED

• LEDs allow current to flow in only one direction
• Positive voltage applied to the anode
• Cathode connected to Ground

Current Flow in RGB LEDs

• RGB LEDs operate in general same way
• Current flows from anode to cathode
• Positive voltage on anode causes LED to turn on
• But there is a small catch to beware of…
  • There are two types of RGB LEDs

Common Cathode Wiring

• R, G, B pins are anode (positive)
• Connect cathode (longer pin) to Ground (negative)
• Output HIGH (3.3v) on anode turns on, LOW turns off
• This is what we use in class

Common Cathode Wiring

Common Cathode RGB LEDs

• …are physically the opposite of regular LEDs
  • Regular LED: anode is longer pin
  • Common cathode RGB LED: cathode is longer pin
• …are wired the same as regular LEDs
  • Connect anode to Photon 2
  • Output HIGH to turn on

Common Anode Wiring

• R, G, B pins are cathode (negative)
• Connect anode (longer pin) to 3.3v (positive)
• Output LOW on anode to turn on LED; output HIGH (3.3v) to turn off

Common Anode Wiring

Common Anode RGB LEDs

• …are physically the same as regular LEDs
  • LED: anode is longer pin
  • Common anode RGB LED: anode is longer pin
• …are wired the opposite as regular LEDs
  • Connect anode to power
  • Output LOW to turn on

Color Mixing

• Check out https://htmlcolorcodes.com/ to see how R, G, and B mix to create colors

R + G + B = ?

Color Mixing with RGB LEDs

• R + G + B ≠ W
• Due to variations in manufacturing and resistor tolerances

Lab 1

Lab 1 steps

• Stage 1: Create a latch so the on-board LED turn on and stays on when the button is pressed, and the on-board LED turns off and stays off when the button is pressed again
• Stage 2: Change the firmware so when the button is pressed, the following light sequence is displayed on the RGB LED
  • red for 1/2 sec
  • green for 1/2 sec
  • blue for 1/2 sec
  • orange for 1/2 sec
• Stage 3: Change the firmware so when the button is pressed, a random color is show on the RGB LED

Lab 2

Lab 2 steps

1. Wire an RGB LED
2. Wire potentiometer
3. Create code to allow potentiometer to control only the brightness of the red LED, and have the blue and green LED always on
4. Then, allow the potentiometer to control the brightness of all LEDs

Lab 3

Lab 3 steps

1. Wire an RGB LED
2. When switch is to one direction, display your favorite color
3. When switch is other direction, display a random color
4. Rewrite sketch using displayColor(r, g, b) and displayRandomColor()
5. Import rgb-controls library to animate colors

Credit

• CC BY-SA 3.0, Source
• Sparkfun
• Images created with Fritzing