We worked on different small powerful projects. the major one was smart charger.
The idea of the device (Smart Charger) is to protect the battery from over charging. The working of this device is as follows.
Arduino is the major component of this device which will control all the rest components (LCD, Keypad and Relay) connected to each other.
First of all we will convert 220V to 5V by using step down transformer to operate the Arduino. We will also give 220V to relay as soon as Arduino will operate the relay 220V directly goes to the socket.
Now as we turn on our device the instructions will be shown on the LCD. Then we will set the time (hours and minutes) by using keypad. After setting the time we will press the # twice from keypad which will act as Enter key. After pressing # the counter will start and Arduino will operate the relay, as soon as relay operates, it will give 220V from the AC source to socket and our mobile will start charging. The mobile will be charged for the sake of particular time that we set on the counter. After the charging process complete then Arduino will give signal to the relay, and relay will cut off the voltage (220V) to the socket and our charger will be disconnected, and a message timeout will be shown on the LCD.