How to properly use 555 timer

The 555 timer is the most popular integrated chip. It is used as oscillator in electronics circuits, the 555 timer is capable of being used in astable and mono stable circuits. Its output always alternates between VCC and zero volts. 555 timer is usually used in counter IC's and where we need clock pulse, so it is important to know how to properly wire 555 timer circuit and how to set required duty cycle of output clock. 
You can set duty cycle of output clock by changing the values of R1, R2 and C1 as follows
1-    Increasing R1 will increase High Time and increase Low time.
2-    Increasing R2 will increase High Time but will not change low time
3-    Changing C1 will change cycle time and reduce the frequency of output generated clock.
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Note: If your timer is not working check pin number 4 (Reset Pin), as you can see in diagram pin 4 is active low so make sure it is connected to positive terminal.