In this project two new sensors (DHT11 and HC-SR04) are used with arduino. In the Arduino programming loop following code is used:
float DHT11_humidity = 0.0;
float DHT11_temperature = 0.0;
int chk = DHT11.read(DHT11PIN);
if(chk == 0)//if chk is zero it works properly
{
DHT11_humidity = (float)DHT11.humidity;
DHT11_temperature = (float)DHT11.temperature;
}
lcd.setCursor(0, 0);
lcd.print("H%:");
lcd.print(DHT11_humidity);
lcd.print(" TC:");
lcd.print(DHT11_temperature);
//HC-SR04
long duration, distance;
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH); distance = (duration/2) / 29.1;
if (distance >= 400 || distance <= 2)
{
lcd.print(" Dcm: NA");
lcd.print(" ");}
else
{
lcd.print(" Dcm: ");
lcd.print(distance);
lcd.print(" ");}
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| DHT11 Humidity & Temperature Sensor |
The DHT11 is a basic, digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed). DHT11 specifications are:
- Power supply: 3.0 to 5.5V DC
- Output signal: digital signal via single-bus
- Operating range: humidity 20 to 90%RH, temperature 0 to 50℃
- Interchangeability: fully interchangeable
- Range of meauring humidity: 20％ to 90%RH(0－50℃temperature compensation）
- Range of meauring temperature: 0 to +50℃
- Accuracy of measuring humidity: ±5.0%RH
- Accuracy of measuring temperature: ±2.0℃
- Response time: <5s
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| HC-SR04 Ultrasonic Distance Sensor |
Ultrasonic ranging module HC-SR04 provides 2cm - 400cm non-contact measurement function, the ranging accuracy can reach to 3mm. The modules includes ultrasonic transmitters, receiver and control circuit. The basic principle of work:
(1) Using IO trigger for at least 10us high level signal,
(2) The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back.
(3) IF the signal back, through high level , time of high output IO duration is the time from sending ultrasonic to returning.16x2 LCD displays DHT11 measured humidity as % and temperature in degrees centigrade. Light value is mapped to between 0 and 255. Distance in cm measured by HC-SR04.
The arduino pins are as follows:
//Arduino pins used for LCD
LiquidCrystal lcd(12, 11, 7, 6, 5, 4);
//Arduino pin for DHT11
#define DHT11PIN 13
//Arduino pins for HC-SR04
#define trigPin 9
#define echoPin 2
//Arduino pin for photocell
int photocellPin = A0;
//Arduino pins used for LED RGB
const int red = 3;
const int green = 8;
const int blue = 10;
I also suggest you to read Professional Android Sensor Programming
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