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.
The 555 timer has the given pin layout:
It also has the standard circuit as:
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:
- f is the frequency of the oscillation
- C is the capacitance in Farad
- R is the 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.
Pictorials:
Pictorials:
