Humidity sensor with led alarm | Arduino project

This page contains Arduino Humidity sensor with led alarm source code. This project is good for someone who wants to make a humidity meter or hygrometer with led alarm if humidity and temperature over a threshold. It's easy to make and doesn't require an external power supply, just use power from an Arduino UNO R3 board (USB power compatible with this project).

Electronic components list:
1 x Arduino Uno R3
1x 20 x4 I2C LCD display
1 x AM 2320 humidity/temp sensor
1 x 5 mm led ( 2 x if you plan to use led for pin 13 instead built-in led)
1 x 1000 ohms resistor ( 2 x if you plan to use led for pin 13 instead built-in led)
Any USB power adapter, 500 mA current at least.

Here is the Arduino code:
AM 2320 library
LCD display i2c library

#include <Wire.h>
#include <AM2320.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x3F, 20, 4);
AM2320 th;
int led2 = 12;

How to repair lcd display problem without paying any money.

My multimeter LCD had the annoying big black spot on it. That made me hard to read numbers, so I decided to fix it without paying money because the multimeter cost not high.

This method is not cost you at all because the material I used was in my bin.

All you need:
a piece of paper

See before and after picture below.

Why old LCD display always have black spots?

Because when LCD display exposes to sunlight, the moisture is slowly degrading glue that attaches to mirror foil. If you do not keep the multimeter away from moisture or the sunlight the multimeter's LCD display will be worst until you cannot see anything.

Below is the video that shows you how to repair the problem completely.