The Door Buzzer

1 Transistors

Learn It

  • In this project you're going to make an electronic door buzzer, like the one shown below.

Learn It

  • To activate the buzzer and the LED, we're going to use a circuit component called a transistor.
  • In this lesson you'll learn what a transistor is and how it can be used as an electronic switch

Learn It

Transistors-white.jpg

  • Transistors come in many shapes and sizes, but they all have one thing in common.

Research It

  • All transistors have three legs - a collector, a base and an emitter.
  • The type of transistor you're going to be using is a BC547B, which looks like this.

bc547b.png

  • Use online resources to help you label the picture above, to show which legs are which.

Try It

  • The circuit symbol for a transistor looks like this.

200px-BJT_symbol_NPN.svg.png

  • The legs have been labelled B,C and E.
  • Now look at the simulation below. This shows a transistor connected to a 5V Power supply, with an LED.

transistor.gif

  • Connected to the base of the transistor is a signal generator.
  • The signal generator produces a varying voltage, going from 0 up to 5V and then back down again.
  • The voltmeter will tell you the voltage being produced by the signal generator.

Badge It

  • Try and explain what is causing the LED to switch on and off again.
  • Make sure your are using the following terms:
    1. Base
    2. Collector
    3. Emitter
    4. Signal Generator
    5. LED
    6. Current
    7. Voltage