555 Timer

The 555 timer is used as a timer, pulse generator and oscillator, etc. The 555 timer has 3 

modes, namely, monostable, astable and bistable modes. Each have different usage and effects 

on the 555 timer. Here in this example, we will use the 555 timer in astable mode making use 

of it as an oscillator.

Here is a given pin layout of the 555 Timer:

This also has a standard circuit as shown below:

The resistances can be assumed. After having an assumed value for the resistors, the value 


for the capacitance can be computed using the given formula:

where:

Ø  f = frequency of the oscillation

Ø  C = is the capacitance in Farad

Ø  R = Resistance in ohms

Using the computed and assumed values, we can now construct a 555 timer circuit. To 


realize the resulting oscillation, we will connect a LED to the output. This will make the LED 


blink slowly or fast depending on frequency of the oscillation. Higher frequencies will tend to 


make the LED blink at a very fast rate that it will appear as though it did not turn off at all.

As for our final output, here is what we have: