POWER JACK CABLE / USB PORT: This Arduino atmega-328 microcontroller can be connected with the other electronic devices by using USB port or power jack cable. Before initializing Arduino user need to code program from computer to the Arduino through usb cable . After code have been upload, the usb can be ejected and the Arduino can be used as a standalone device.POWER SUPPLY: Power supply port is exist at the corner of the arduino. Arduino is powered up by connecting either using external power supply such as ac power supply, or by using dc power supply connected to pins. These power supply is important as a source of energy for Arduino. Arduino can only accepted certain amount of voltage and for Arduino atmega 328 it can only accepted from 0V to 5V. Arduino can be damaged if voltage higher than the required is used.WORKING PRINCIPLE The working of arduino microcontroller is where the proper connection is made. Checking all the input ports as well as the power supply connection. The output of the pins can be connected with the external devices according to their applications. The program to be executed for the applications can be done by using arduino software. From this arduino software, we can edit according to the applications. This software can works on c and c++ programming language. It is fully a high level language. By using the conditions of working, we can create a program to proceed for the applications. Then after, these programs can be uploaded through the arduino microcontroller by using the power jack cable. The program can be uploaded to the microcontroller and ready for further process. ATMEGA-328 microcontroller can saves a program and these IC can acts as a processor to do the process without any error. After by giving an analog or digital input to the system, we can do the process according to the applications. We can control the process of the application by editing the program in the arduino software and again can be uploaded to the arduino microcontroller via power jack cable. There is an option of reset button. The purpose of reset button is to reset the program which means the previous programs are deleted and we can use the arduino for the other application purposes. Likewise, these arduino ATMEGA-328 microcontrollers can be used for n number of applications. These arduino microcontrollers are widely used in automation industries for controlling the process and to work the system in an automation mode.