User Manual

Lesson 9 Ne555

Introduction

If you ask anyone in the know to rank the most commonly and widely used IC, the famous

555 time base IC would certainly be at the top of the list. The 555 – a mixed circuit composed

of analog and digital circuits – integrates analogue and logical functions into an

independent I C, and hence tremendously expands the application range of analog

integrated circuits. The 555 is widely used in v arious timers, pulse generators, and oscillators.

Components

- 1 * Raspberry Pi

- 1 * Breadboard

- 1 * NE555

- 2 * 104 ceramic capacitor

- 1 * Potentiometer (50KΩ)

- 1 * Resistor (10KΩ)

- 1 * USB cable

- Jumper wires

Principle

The 555 IC was originally used as a timer, hence the name 555 time base circuit. It is now

widely used in various electronic products because of its reliability, conv enience, and low

price. The 555 is a complex hybrid circuit with dozens of components such as a divider,

comparator, basic R-S trigger, discharge tube, and buffer.

555 chip pins are introduced as follows:

As shown in the picture, the 555 IC is dual in-line with the 8-pin package. Thus:

 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;

 Pin 4 (RESET): output low lev el when supplied a low one;

 Pin 5 (CONTROL VOLTAGE): changing the upper and lower level trigger values;

 Pin 6 (THRESHOLD): the input of upper comparator;

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