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;

lm3914 schematic diagram and test

If you want to make a simple VU meter. LM3914 is the best choice for you. It's easy to make VU meter or 10 dot/bar DC level meter with lm3914. 

lm 3914 can withstand +-35 volts input without any damage so you can make VU meter even you are new in electronic DIY.

The circuit uses minimal component to make the job done.
List of component:
R1 = 1 kilo-ohms
R2,R3 = 4.7 kilo-ohms
R4 = 10 kilo-ohms
ic = lm 3914n-1 (lm3914)
C1 = 4.7 uf at least to 47 uf (better bass respond)
10 LEDs red,green,yellow,orange or whatever you want
9 - 12 volts DC power supply

LM3914 schematic diagram

   Lm3914 VU meter video, the video show step by step guide and circuit explanation.

Now, I add a sine wave rectifier circuit to lm3914, it makes the dot mode more accuracy.

Real dot mode VU meter schematic diagram


  1. 👌 Thanks for great idea for me. Actually I'm not expart. But I'm really interested. Actually i want to build a music vu meter. & I did it by using LM3914 IC with a basic circuit diagram. & I found actually what i want. Sorry for my bad English.

    1. You're welcome. I'm not an English expert so don't worry about it

  2. Sir i need a little help from you. 1➡I don't have 1n4048 diode. Can i replace with 1n4148???

  3. Thanks again & again.
    ➡I want to add more then 10 led using 1 lm3914. Is it possible?


Post a Comment