Hello, does anyone knows how to use two DHT11 sensors at same time?
There is a tutorial about using DHT11s here.
They say:
You can add as many DHT sensors as you line on individual pins, just add new lines such as
DHT dht2 = DHT(pin, type);
below the declaration for the initial dht object, and you can reference the new dht2 whenever you like.
Just connect the data pin of each sensor to a different pin
Thank you! so how should i do it in this code?
Im relative new at arduino...
For example i write: #define DHT11_PIN 8 how should i continue?
/*
Program to demonstrate Data Logging/Visualisation using Arduino
###Connection with SD card module###
Vcc->5V
Gnd->Gnd
MISO->pin 12
MOSI->pin 11
SCK-> pin 13
CS-> pin 4
###Connection with DS3231###
Vcc->5V
Gns->Gnd
SCL->pin A5
SDA-> pin A4
###Connection with DT11###
Vcc->5V
Gnd->Gnd
Out-> pin 7
*/
#include <RTClib.h> //Library for RTC module (Download from Link in article)
#include <Wire.h>
#include <SPI.h> //Library for SPI communication (Pre-Loaded into Arduino)
#include <SD.h> //Library for SD card (Pre-Loaded into Arduino)
#include <dht.h> //Library for dht11 Temperature and Humidity sensor (Download from Link in article)
#define DHT11_PIN 7 //Sensor output pin is connected to pin 7
dht DHT; //Sensor object named as DHT
RTC_DS3231 rtc;
const int chipSelect = 4; //SD card CS pin connected to pin 4 of Arduino
void setup() {
Serial.begin(9600);
Initialize_SDcard();
rtc.begin();
}
void loop() {
Write_SDcard();
delay(5000); //Wait for 5 seconds before writing the next data
}
void Write_SDcard() {
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
int chk = DHT.read11(DHT11_PIN);
float t = DHT.temperature;
float h = DHT.humidity;
Serial.println(t, 1);
Serial.println(h, 1);
DateTime now = rtc.now();
File dataFile = SD.open("LoggerCD.txt", FILE_WRITE);
// if the file is available, write to it:
if (dataFile) {
char bufer[50];
sprintf(bufer, "%02u.%02u.%02u,%02u:%02u:%02u,%0u.%0u,%0u.%0u\r\n",
now.year(),
now.month(),
now.day(),
now.hour(),
now.minute(),
now.second(),
uint16_t(floor(t)), uint16_t(t * 10) % 10,
uint16_t(floor(h)), uint16_t(h * 10) % 10
);
dataFile.print(bufer);
dataFile.close(); //Close the file
}
else
Serial.println("OOPS!! SD card writing failed");
}
void Initialize_SDcard() {
// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
Serial.println("Card failed, or not present");
// don't do anything more:
return;
}
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
File dataFile = SD.open("LoggerCD.txt", FILE_WRITE);
// if the file is available, write to it:
if (dataFile) {
dataFile.println("Date,Time,Temperature,Humidity"); //Write the first row of the excel file
dataFile.close();
}
}
Write another line, just like that but with a different pin number and a different name
#define DHT11_PIN1 7
#define DHT11_PIN2 8
and then, create two DHT objects
dht DHT1;
dht DHT2;
and then, everywhere in your code, you use the variable DHT1 if you want to talk to sensor 1 and DHT2 if you want to talk to sensor 2
Thank you!
Do you know what i did wrong? The values in the serial monitor of the second sensor are always 0,00 and in the file on the sd card they aren`t mentioned...
/*
Program to demonstrate Data Logging/Visualisation using Arduino
###Connection with SD card module###
Vcc->5V
Gnd->Gnd
MISO->pin 12
MOSI->pin 11
SCK-> pin 13
CS-> pin 4
###Connection with DS3231###
Vcc->5V
Gns->Gnd
SCL->pin A5
SDA-> pin A4
###Connection with DT11###
Vcc->5V
Gnd->Gnd
Out-> pin 7
*/
#include <RTClib.h> //Library for RTC module (Download from Link in article)
#include <Wire.h>
#include <SPI.h> //Library for SPI communication (Pre-Loaded into Arduino)
#include <SD.h> //Library for SD card (Pre-Loaded into Arduino)
#include <dht.h> //Library for dht11 Temperature and Humidity sensor (Download from Link in article)
#define DHT11_PIN1 7 //Sensor output pin is connected to pin 7
#define DHT11_PIN2 8
dht DHT1; //Sensor object named as DHT
dht DHT2;
RTC_DS3231 rtc;
const int chipSelect = 4; //SD card CS pin connected to pin 4 of Arduino
void setup() {
Serial.begin(9600);
Initialize_SDcard();
rtc.begin();
}
void loop() {
Write_SDcard();
delay(5000); //Wait for 5 seconds before writing the next data
}
void Write_SDcard() {
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
int chk = DHT1.read11(DHT11_PIN1);DHT2.read11(DHT11_PIN2);
float t = DHT1.temperature;
float h = DHT1.humidity;
float t1 = DHT2.temperature;
float h1 = DHT2.humidity;
Serial.println(t, 1);
Serial.println(h, 1);
Serial.println(t1, 1);
Serial.println(h1, 1);
DateTime now = rtc.now();
File dataFile = SD.open("LoggerCD.txt", FILE_WRITE);
// if the file is available, write to it:
if (dataFile) {
char bufer[50];
sprintf(bufer, "%02u.%02u.%02u,%02u:%02u:%02u,%0u.%0u,%0u.%0u\r\n",
now.year(),
now.month(),
now.day(),
now.hour(),
now.minute(),
now.second(),
uint16_t(floor(t)), uint16_t(t * 10) % 10,
uint16_t(floor(h)), uint16_t(h * 10) % 10,
uint16_t(floor(t1)), uint16_t(t * 10) % 10,
uint16_t(floor(h1)), uint16_t(h * 10) % 10
);
dataFile.print(bufer);
dataFile.close(); //Close the file
}
else
Serial.println("OOPS!! SD card writing failed");
}
void Initialize_SDcard() {
// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
Serial.println("Card failed, or not present");
// don't do anything more:
return;
}
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
File dataFile = SD.open("LoggerCD.txt", FILE_WRITE);
// if the file is available, write to it:
if (dataFile) {
dataFile.println("Date,Time,Temperature,Humidity"); //Write the first row of the excel file
dataFile.close();
}
}
I think the SD is not getting the data from the DHT2 because the format string should be
`sprintf(bufer, "%02u.%02u.%02u,%02u:%02u:%02u,%0u.%0u,%0u.%0u,%0u.%0u,%0u.%0u\r\n",`
// YY MM DD hh mm ss t1 t1 h1 h1 t2 t2 h2 h2
And, just to check what may be wrong with DHT2 I would do several tests, such as
switching pins in the following declarations
In case you now get good readings from DHT2 and not from DHT1, I would think of a hardware issue. Check that both sensors are of the same type, especially if you are using the kind that comes in a little board. The board pinouts can be different.
1 Like
This format string defines 10 fields. You have provided 4 additional ones (the second sensor) but have not included them in the specification.
It appears you need to take some time and learn a bit about C/C++ just like we all did.
Also,
needs to use the variables t1 and h1 in both equations [the ones after the comma]
As for why you are reading 0 - is it wired up correctly? How about a picture of your setup?
1 Like
Thank you very much!! Now it works like i wanted!!
Now everything is perfect, my setup is a bit chaotic, but i will revise it...
Yeah, i will learn a more about C/C++
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