User Manual

45
Lesson 9 555 Timer
Introduction
The NE555 Timer, a mixed circuit composed of analog and digital circuits, integrates analog
and logical functions into an independent IC, thus tremendously expanding the
applications of analog integrated circuits. It is widely used in various timers, pulse
generators, and oscillators. In this lesson, we will learn how to use the 555 timer.
Components
- 1 * Raspberry Pi
- 1 * Breadboard
- 1 * NE555
- 3 * Resistor (1 * 1KΩ, 2 * 10KΩ)
- 2 * Capacitor (100nF)
- Jumper wires
Principle
555 IC
A 555 timer is a medium-sized IC device which combines analog and digital functions. With
low cost and reliable performance, it just attaches external resistors and capacitors so as to
achieve the functions of multivibrator, monostable trigger, Schmitt trigger and other circuits
which can generate and transform pulses. It is also used frequently as a timer and widely
applied to instruments, household appliances, electronic measurement, automatic control
and other fields.
Its pins and their functions:
As shown in the picture, the pins are set dual in-line with the 8-pin package.
 Pin 1 (GND): the ground
 Pin 2 (TRIGGER ): the input of lower comparator
 Pin 3 (OUTPUT): having two states of 0 and 1 decided by the input electrical level