Light Emitting Diode9(LED)
- 1. Light Emitting Diode: LED
- 2. What is an LED? Light-emitting diode Semiconductor Has polarity
- 3. LED: How It Works When current flows across a diode Negative electrons move one way and positive holes move the other way
- 4. LED: How It Works The wholes exist at a lower energy level than the free electrons Therefore when a free electrons falls it losses energy
- 5. LED: How It Works This energy is emitted in a form of a photon, which causes light The color of the light is determined by the fall of the electron and hence energy level of the photon
- 6. Inside a Light Emitting Diode Transparent Plastic Case Terminal Pins Diode
- 8. How to Connect a LED: Requires 1.5~2.5V and 10 mA To prevent overloading, use resistor 470 Ω
- 9. How to Connect a LED:
- 10. Connect LED to BS2 LED is on when P0 is high LED is on when P1 is low
- 11. Connect Multiple LEDs to BS2 8 LEDs are connected to BS2 each I/O pin (P0-P7) is allowed to sink 6.25mA
- 12. Case Study: Blinking LED
- 13. Case Study: Blinking LED Pbasic program to make an LED blink output 0 Main: low 0 pause 1000 high 0 pause 1000 goto Main Make pin0 an output Loop begins here Turn LED on Pause for 1 sec Turn LED off Pause for 1 sec Go back to beginning of loop
- 14. Experiments Flash an LED Single LED Multiple LEDs Traffic Light by use of LEDs