Grove Temperature and Humidity Sensor

Hi, I am connecting Grove Temp & Hum Sensor to XBee Carrier + Wifi Bee, I am using the library in the Wiki and use the example like this :

[code]// Example testing sketch for various DHT humidity/temperature sensors
// Written by ladyada, public domain

#include “DHT.h”

#define DHTPIN 2 // what pin we’re connected to

// Uncomment whatever type you’re using!
#define DHTTYPE DHT11 // DHT 11
//#define DHTTYPE DHT22 // DHT 22 (AM2302)
//#define DHTTYPE DHT21 // DHT 21 (AM2301)

// Connect pin 1 (on the left) of the sensor to +5V
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

DHT dht(DHTPIN, DHTTYPE);

void setup() {
Serial.begin(9600);
Serial.println(“DHTxx test!”);

dht.begin();
}

void loop() {
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds ‘old’ (its a very slow sensor)
float h = dht.readHumidity();
float t = dht.readTemperature();

// check if returns are valid, if they are NaN (not a number) then something went wrong!
if (isnan(t) || isnan(h)) {
Serial.println(“Failed to read from DHT”);
} else {
Serial.print(“Humidity: “);
Serial.print(h);
Serial.print(” %\t”);
Serial.print(“Temperature: “);
Serial.print(t);
Serial.println(” *C”);
}
}[/code]

but the result is :

DHTxx test! Read failFailed to read from DHT Humidity: 0.00 % Temperature: 0.00 *C Humidity: 0.00 % Temperature: 0.00 *C Humidity: 0.00 % Temperature: 0.00 *C

==============
and then I tried to use another code :

[code]/* YourDuino.com Example Software Sketch
DHT11 Humidity and Temperature Sensor test
Credits: Rob Tillaart
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=162
terry@yourduino.com */

/-----( Import needed libraries )-----/
#include <dht11.h>

/-----( Declare objects )-----/
dht11 DHT11;

/-----( Declare Constants, Pin Numbers )-----/
#define DHT11PIN 2

void setup() /----( SETUP: RUNS ONCE )----/
{
Serial.begin(9600);
Serial.println("DHT11 TEST PROGRAM ");
Serial.print("LIBRARY VERSION: ");
Serial.println(DHT11LIB_VERSION);
Serial.println();
}/–(end setup )—/

void loop() /----( LOOP: RUNS CONSTANTLY )----/
{
Serial.println("\n");

int chk = DHT11.read(DHT11PIN);

Serial.print("Read sensor: ");
switch (chk)
{
case 0: Serial.println(“OK”); break;
case -1: Serial.println(“Checksum error”); break;
case -2: Serial.println(“Time out error”); break;
default: Serial.println(“Unknown error”); break;
}

Serial.print("Humidity (%): ");
Serial.println((float)DHT11.humidity, 2);

Serial.print("Temperature (oC): ");
Serial.println((float)DHT11.temperature, 2);

Serial.print("Temperature (oF): ");
Serial.println(Fahrenheit(DHT11.temperature), 2);

Serial.print("Temperature (K): ");
Serial.println(Kelvin(DHT11.temperature), 2);

Serial.print("Dew Point (oC): ");
Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));

Serial.print("Dew PointFast (oC): ");
Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));

delay(2000);
}/* --(end main loop )-- */

/-----( Declare User-written Functions )-----/
//
//Celsius to Fahrenheit conversion
double Fahrenheit(double celsius)
{
return 1.8 * celsius + 32;
}

//Celsius to Kelvin conversion
double Kelvin(double celsius)
{
return celsius + 273.15;
}

// dewPoint function NOAA
// reference: http://wahiduddin.net/calc/density_algorithms.htm
double dewPoint(double celsius, double humidity)
{
double A0= 373.15/(273.15 + celsius);
double SUM = -7.90298 * (A0-1);
SUM += 5.02808 * log10(A0);
SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
SUM += log10(1013.246);
double VP = pow(10, SUM-3) * humidity;
double T = log(VP/0.61078); // temp var
return (241.88 * T) / (17.558-T);
}

// delta max = 0.6544 wrt dewPoint()
// 5x faster than dewPoint()
// reference: http://en.wikipedia.org/wiki/Dew_point
double dewPointFast(double celsius, double humidity)
{
double a = 17.271;
double b = 237.7;
double temp = (a * celsius) / (b + celsius) + log(humidity/100);
double Td = (b * temp) / (a - temp);
return Td;
}

/* ( THE END ) */
[/code]

and the result is :

[code]DHT11 TEST PROGRAM
LIBRARY VERSION: 0.3.2

Read sensor: Time out error
Humidity (%): 0.00
Temperature (oC): 0.00
Temperature (oF): 32.00
Temperature (K): 273.15
Dew Point (oC): nan
Dew PointFast (oC): nan
[/code]

I was wondering that the cause is the I/O pin, in both code above they use pin 2 but when I googling around I found that the code is for DHT11 like this :

pin 1 = VCC
pin 2 = Signal/Data
pin 3 = NC/Not Connected
pin 4 = Ground
not a Grove like I am using :

that’s why the both code use pin 2, so I tried to change it to pin 5 as discribed in Xbee Carrier Wiki, although I am not sure that pin 5 means D5 and pin 6 means D6 Grove Connector:

and when I carefully look at the cable, everything is at the right place :
Cable Colour == Xbee Carrier == Grove Temp Hum
Yellow == D5 == SIG
White == D6 == NC
Red == VCC == VCC
Black == Ground == Ground
but the result is the same, timeout or communication failed, anyone can help?

#sorry for my bad english

hi, do you have a multimeter by hand? Can you chenk if the Vcc pin 3.3V ?
btw~ you english is more good than mine~ :smiley:

My friend has just checked VCC pin on both the sensor and Xbee Carrier and the result is around 3.8 V. So, I think that should be enough to powering the sensor.

#nope, my english is not as good as you think :stuck_out_tongue:

I tried another code again from here :

[code]#define dht11_pin 14 //Analog port 0 on Arduino Uno
//#define dht11_pin 54 //Analog port 0 on Arduino Mega2560

byte read_dht11_dat()
{
byte i = 0;
byte result=0;
for(i=0; i< 8; i++)
{
while (!digitalRead(dht11_pin));
delayMicroseconds(30);
if (digitalRead(dht11_pin) != 0 )
bitSet(result, 7-i);
while (digitalRead(dht11_pin));
}
return result;
}

void setup()
{
pinMode(dht11_pin, OUTPUT);
digitalWrite(dht11_pin, HIGH);
Serial.begin(9600);
Serial.println(“Ready”);
}

void loop()
{
byte dht11_dat[5];
byte dht11_in;
byte i;// start condition

digitalWrite(dht11_pin, LOW);
delay(18);
digitalWrite(dht11_pin, HIGH);
delayMicroseconds(1);
pinMode(dht11_pin, INPUT);
delayMicroseconds(40);

if (digitalRead(dht11_pin))
{
Serial.println(“dht11 start condition 1 not met”); // wait for DHT response signal: LOW
delay(1000);
return;
}
delayMicroseconds(80);
if (!digitalRead(dht11_pin))
{
Serial.println(“dht11 start condition 2 not met”); //wair for second response signal:HIGH
return;
}

delayMicroseconds(80);// now ready for data reception
for (i=0; i<5; i++)
{ dht11_dat[i] = read_dht11_dat();} //recieved 40 bits data. Details are described in datasheet

pinMode(dht11_pin, OUTPUT);
digitalWrite(dht11_pin, HIGH);
byte dht11_check_sum = dht11_dat[0]+dht11_dat[2];// check check_sum
if(dht11_dat[4]!= dht11_check_sum)
{
Serial.println(“DHT11 checksum error”);
}
Serial.print("Current humdity = “);
Serial.print(dht11_dat[0], DEC);
Serial.print(”% ");
Serial.print("temperature = ");
Serial.print(dht11_dat[2], DEC);
Serial.println("C ");
delay(2000); //fresh time
}[/code]

the result :

Ready dht11 start condition 1 not met dht11 start condition 1 not met dht11 start condition 1 not met dht11 start condition 1 not met dht11 start condition 1 not met dht11 start condition 1 not met

I also asked on “Question & Answer” section in Xbee Carrier product guide and Jacket Chueng answered :

anyone can give me some more detail what should I do? I am a newbie on Arduino and microcontroller, I just want to make a simple project and develop it later after this has been success.

Ok since I bought this sensor from Gerai Cerdas in my country, so I asked them to check the sensor in case if it is broken, but they said there is no problem. Then I emailed them about this problem and they answered that those sketches I’ve tried is only for simple circuit like Uno, Mega, etc. and told me to make a simple webserver to send the temperature & humidity value but I dont know how to do that, I am only able to send RAW value from sensor to webserver and store it into MySQL and then show the statistic from MySQL to webserver, I am using Wifi Bee and WiShield/WiServer library and it works fine (only RAW value from the sensor). I’ve searched over the internet for 2 months and already posted in some forums but still not solved.

Can anyone teach me how to extract temperature & humidity value? fist I have to try to show in Serial Monitor, if it works then I will go to WiServer.
Here is DHT11 Datasheet if needed :
http://www.micro4you.com/files/sensor/DHT11.pdf

Thanks in advance.
#sorry for my bad english

I look again to Wifi Bee wiki for pin definition :

and try again the sketch :

[code]// Example testing sketch for various DHT humidity/temperature sensors
// Written by ladyada, public domain

#include <DHT.h>

#define DHTPIN 5 // what pin we’re connected to

// Uncomment whatever type you’re using!
#define DHTTYPE DHT11 // DHT 11
//#define DHTTYPE DHT22 // DHT 22 (AM2302)
//#define DHTTYPE DHT21 // DHT 21 (AM2301)

// Connect pin 1 (on the left) of the sensor to +5V
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

DHT dht(DHTPIN, DHTTYPE);

void setup() {
Serial.begin(9600);
Serial.println(“DHTxx test!”);

dht.begin();
}

void loop() {
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds ‘old’ (its a very slow sensor)
float h = dht.readHumidity();
float t = dht.readTemperature();
unsigned char sensorValue = analogRead(5);

// check if returns are valid, if they are NaN (not a number) then something went wrong!
if (isnan(t) || isnan(h)) {
Serial.println(“Failed to read from DHT”);
} else {
Serial.print(“Humidity: “);
Serial.print(h);
Serial.print(” %\t”);
Serial.print(“Temperature: “);
Serial.print(t);
Serial.println(” *C”);
Serial.print("RAW value : ");
Serial.println(sensorValue);
}
}[/code]

but the result still same although it can read RAW value from sensor :

then I move the sensor from D5,D6 to I2C Grove Connector and changed the DHTPIN from 5 to 19 and it works!! XD

Not sure how it become works because I have already tried to move the sensor to I2C connector but that time still didnt work. And I dont know why pin 5 (PD5) cant read sensor value but pin 19 (SCL) can although pin 5 and 19 both are DIO. Cant believe I have been struggling for 2 months only because of this mistake… -_-’

since my problem is solved then I will continue my project, I were already able to store RAW value and store it into MySQL and show the statistic, and now I only have to change the RAW value with temperature & humidity value… :smiley:
many thanks to all who has been assisting me till now. sorry if this newbie have been being troublesome for you all…