arduino using tachometer

Hi Balaji,

This circuit diagram (click on the link) should be sufficient to connect you IR module to your Arduino. 

Explanation:

The IR module is digital sensor module which works on 5V supply voltage. The module itself will have 3 pins. They are Vcc, Gnd, and Output pin (Here referred as DO for digital output). The Vcc is connected to the 5V pin of the Arduino and the Gnd is conected to Arduino's Gnd. The output of the module is connect to 4th Analog pin A4 (18th pin). 

Hope that answered your question, if not let me know your quires in detail. 

Thank you!