555 clock circuit
555 is an IC used to generate a clock .The two attributes of a clock are
- Duty cycle.
Pin Configuration of 555
Both of these can be changed using this IC, however the duty cycle is always <50%. There are two modes in which 555 can run.
As the name suggests; in this mode the output is stable in only one (mono) state i.e. ‘off’ state. Thus it can stay only for a finite time, if triggered, to the other state i.e. ‘on’ state. This time can be set choosing appropriate values of resistances in the formula:
T = 1.1 x R1 x C1
555 in monostable mode
A stable mode
In this mode; the output is stable neither in ‘high’ state nor in ‘low’ state. Hence it oscillates from one state to another giving us a square wave or clock. We can set the clock frequency and Duty cycle D by the formula:
NOTE: Capacitor C2 is just to filter the noise and its value can be suitably chosen to be 0.01μF. It can also be neglected.