handheld water temperature monitoring system.
A 5 voltage power supply, a USB for ICStation Mega, a ICStation Mega development board compatible with Arduino, a breadboard, a 1602 LCD module, a DS18B20 temperature detecting probe, a buzzer module, three switches, five 1K resistors, a 10K resistors, a adjustable resistors, a red LED, a yellow LED and 31 jumper wires.

Next, we will briefly introduce the working principle of this handheld water temperature monitoring system.
This system can detect the temperature by the DS18B20 probe. You can set a highest temperature and lowest temperature by the switches. The temperature that DS18B20 detects, the highest temperature and the lowest temperature will display on the 1602LCD. When the DS18B20 probe detects that the temperature is higher than the highest temperature, the buzzer module will alarm, and the red LED will light. When the temperature is below the lowest temperature, the buzzer will alarm,and  the yellow LED will light. 

When start up, the 1602 LCD will display the current temperature that the DS18B20 detects. You can see the current temperature is 31 centigrade, the highest temperature is 40 centigrade, the lowest temperature is 20 centigrade. The key1 and key2 are used to adjust the temperature. The key3 is to switch between the setting of highest temperature and lowest temperature. Here are two bottles of water, a bottle of hot water, and another is the cold water. Now we set the highest temperature 45 centigrade and lowest temperature is the 15 centigrade. 

When we put the temperature probe into the hot water, the probe detects that the temperature of hot water is higher than the highest temperature, the buzzer will alarm and the red LED lights. Then we put the probe into the cold water, and wait for a while, the probe detects that the temperature of cold water is below the lowest value, the buzzer will alarm, and the yellow LED lights.  [email][/email]