Introduction

I’ve remember when I learned about oscillators, multivibrators, flip-flop and so on in the university, it wasn’t pleasant at all..

Example of what horrified me:

tim20.gif

Astable Multivibrator tutorial

But then, I’ve heard how the people of hackaday talks about the Timer 555 as a reference in sentences like:

“An Arduino for that?? I could use a 555 and it will better than your project”

So, I’ve decided to investigate.

What is the timer 555

The wikipedia says:

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element.

In other worlds, it is a small chip, not at all expensive, and very old in the market (From 1970!) but very used in all kind of applications.

The IC 555 has three operating modes: Astable, Monostable and Bistable.

555_Pinout.svg

You can read the datasheet from Texas Instruments

How to use it

This tutorial includes good examples about how to use the timer 555 even if there are hundreds of examples.

On the other hand, the http://www.555-timer-circuits.com/ page describes everything we want to know about this little thing.

And of course, the tutorials from sparkfun can’t miss.

Basic Astable 555 Oscillator Circuit

We are going to build a basic astable with the timer 555. For that, I have two references:

This is a basic layout:

tim47.gif

And the formules to calculate the passive components in function of how much frequency, duty cycle etc, you want

tim49.gif

tim50.gif

With this calculator, we can calculate the passive components that we want for our cycle.

In this case, for a cycle high and low around 350ms each, I choose the components:

  • C = 100uF
  • R1 = 1k
  • R2 = 4.7K

Testing

Simple Output Double Output
PCB_Front.JPG PCB_Back.JPG

Video:

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