DHT11, Arduino Temperature and humidity Sensor.

The DHT11 is a basic,  low-cost digital temperature and humidity sensor.It's fairly simple to use, but requires careful timing to grab data. 

Technical Details


    Low Cost    3 to 5V power and I/O    2.5mA max current    Good for 20-80% humidity readings with 5% accuracy    Good for 0-50°C temperature readings ±2°C accuracy    No more than 1 Hz sampling rate (once every second)    Body size 15.5mm x 12mm x 5.5mm   

Test sketch

//

//   FILE:  dht11_test1.pde

// PURPOSE: DHT11 library test sketch for Arduino

//

#include <dht11.h>

dht11 DHT;

#define DHT11_PIN 7
void setup(){
Serial.begin(9600);
Serial.println("DHT TEST PROGRAM ");
Serial.print("LIBRARY VERSION: ");
Serial.println(DHT11LIB_VERSION);
Serial.println();
Serial.println("Type,\tstatus,\tHumidity (%),\tTemperature (C)");
}
void loop(){
int chk;
Serial.print("DHT11, \t");
chk = DHT.read(DHT11_PIN);    // READ DATA
switch (chk){
case DHTLIB_OK: 
Serial.print("OK,\t");
break;
case DHTLIB_ERROR_CHECKSUM:
Serial.print("Checksum error,\t");
break;
case DHTLIB_ERROR_TIMEOUT:
Serial.print("Time out error,\t");
break;
default:
Serial.print("Unknown error,\t");
break;
}
// DISPLAT DATA

Serial.print(DHT.humidity,1);
Serial.print(",\t");
Serial.println(DHT.temperature,1);
delay(1000);
}

    A tutorial on how to connect a DHT11  Sensor to your 

    Arduino

Simple Arduino Breathalyzer

Simple Arduino Breathalyzer

 Introduction

The MQ series of gas sensors use a small heater inside with an electro-chemical sensor.
They can be calibrated more or less but a know concentration of the measured gas or gasses is needed for that. 
 They are sensitive for a range of gasses and are used indoors at room temperature.
The output is an analog signal and can be read with an analog input of the Arduino. 

SainSmart MQ-3
The analog gas sensor - MQ3 is used in gas leakage detecting equipments in consumer and industry markets, this sensor is suitable for detecting LPG, i-butane, propane, methane ,alcohol, Hydrogen, smoke.
It has a high sensitivity and fast response time.And the sensitivity can be adjusted by the potentiometer.

 The MQ-3 is an alcohol gas sensor that is available for about $5.

 Connetting

 Sensor-Arduino 

    GND - GND
    A0   -  A0
    VCC -   5V


Arduino Schetch

Test Code: 


int val=0;

void setup(){

Serial.begin(9600);
}

void loop(){

val=analogRead(A0);

Serial.println(val);

delay(100);
}

Link App

https://drive.google.com/file/d/1naIS3WD_Boty_EjX_9em6Vw1NMy59dps/view?usp=sharing

Arduino Tutorial - Easy secret knock detector

In this project I build a circuit with a Led and a piezo to function as a on and off a Led when it receives a number of knocking sounds within a given range.

Step 1: Things you need

 Hardware

• LED
• Diode(Zener 5.1v).
• Piezo Buzzer
• 470Ω Resistor
• 1MΩ Resistor
• Arduino uno
• jumper wire
• Breadboard

Software

• Arduino IDE

Step 2: Watch the video tutorial

Step 3: Schematics

 

The circuit is so simple:
Arduino Pins: Breadboard:
Pin A2 --------------------------1MΩ-------------------Gnd
Pin A2 ------------------------Diode-------------------Gnd
Pin A2 ------------------Piezo Buzzer---------------Gnd
Pin 8 -------------------------470Ω-------Led 1------Gnd
Gnd-------------------------------------------------------Gnd

Step 4: Arduino Sketch

"const int outputPin = 5; // led indicator connected to digital pin const int knockSensor = A2; // the piezo is connected to an analog pin const int thresholdHIGH =120; // threshold value to decide when the detected knock is hard (HIGH) const int thresholdLOW = 70; // threshold value to decide when the detected knock is gentle (LOW) const int secretKnockLength = 3; //How many knocks are in your secret knock /* This is the secret knock sequence * 0 represents a LOW or quiet knock * 1 represents a HIGH or loud knock * The sequence can be as long as you like, but longer codes increase the difficulty of matching */ const int secretKnock[secretKnockLength] = {0, 0, 1}; int secretCounter = 0; //this tracks the correct knocks and allows you to move through the sequence int sensorReading = 0; // variable to store the value read from the sensor pin void setup() { //Set the output pin as an OUTPUT pinMode(outputPin, OUTPUT); //Begin Serial Communication. Serial.begin(9600); } void loop() { // read the piezo sensor and store the value in the variable sensorReading: sensorReading = analogRead(knockSensor); // First determine is knock if Hard (HIGH) or Gentle (LOW) //Hard knock (HIGH) is detected if (sensorReading >= thresholdHIGH) { //Check to see if a Hard Knock matches the Secret Knock in the correct sequence. if (secretKnock[secretCounter] == 1) { //The Knock was correct, iterate the counter. secretCounter++; Serial.println("Correct"); } else { //The Knock was incorrect, reset the counter secretCounter = 0; Serial.println("Fail"); digitalWrite(outputPin, LOW); }//close if //Allow some time to pass before sampling again to ensure a clear signal. delay(100); //Gentle knock (LOW) is detected } else if (sensorReading >= thresholdLOW) { //Check to see if a Gentle Knock matches the Secret Knock in the correct sequence. if (secretKnock[secretCounter] == 0) { //The Knock was correct, iterate the counter. secretCounter++; Serial.println("Correct"); } else { //The Knock was incorrect, reset the counter. secretCounter = 0; Serial.println("Fail"); }//close if //Allow some time to pass before sampling again to ensure a clear signal. delay(100); }//close if else //Check for successful entry of the code, by seeing if the entire array has been walked through. if (secretCounter == (secretKnockLength) ) { Serial.println("Welcome"); //if the sececret knock is correct, illuminate the LED for a couple seconds digitalWrite(outputPin, HIGH); //Reset the secret counter to 0. secretCounter = 0; }//close success check }//close loop".