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;

Combine 3 speakers to one amplifier

I saw a question in my Youtube video about how to combine speakers for one amplifier unit without making any damage to an amplifier. 

An speaker impedance must be match or higher than an amplifier manufacturer specification, if you use lower speaker impedance than an amplifier specification, your amplifier may end up damaged or make a fire when you play loud music.

A commercial amplifier can handle between 4 - 16 ohms speaker impedance and maybe lower to 2 ohms for car subwoofer amplifier. but in a question, he asked me how to combine 3 speakers @ 6 ohms load to one amplifier.

The simple solution is to make 3 separate amplifiers and share same input, but it makes the circuit more complicated and uses many electronic components. However, if connect all 3 speakers in series, it will make impedance equal to 18 ohms and it makes an amplifier output drop so much.

So, I use 2 speakers connect in parallel and series to other speakers like an image below

SP 1 and SP 2 impedance drop to 3 ohms because two 6 ohms speakers parallel 
When series the two speakers with SP 3, the speaker's impedance equal to 9 ohms and that suitable to a commercial amplifier in the market.

Remember: When you series speakers the impedance increase = SP1  + SP2 + SPn....
When you parallel speakers, the speakers' impedance decrease = 


  1. Thanks For The Tricks. So two 8 ohms speakers parallel & series the two speakers with 1 4 ohms = 8 ohms total. Am i right. ANS please


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