Husham wanted simple portable temperature logger that would work outside reliably. He’s built electronic part out of several building blocks where control is given to Arduino Nano. Precise time is kept on RTC module based on DS1307. Temperature is measured with LM35 sensor. Data then is logged in to SD card which also is interfaced by using SD card module. Current temperature and time is also displayed on LCD screen.
Special care is taken on building enclosure and adding basic control. So instead of using regular buttons he decided to add couple Hall effect sensors that would act as switches when magnet is brought close to area. One Hall sensor is used to turn LCD backlight and another for resetting microcontroller. Device is powered with couple Li-Ion batteries. Since it only logs data to SD card, eventually you need to take SD card out in order to load data to computer. Probably wireless interface like Bluetooth could make things much easier.