Grove - Temperature&Humidity Sensor

Introduction

This temperature & humidity sensor provides a pre-calibrated digital output. A unique capacitive sensor element measures relative humidity and the temperature is measured by a negative temperature coefficient (NTC) thermistor. It has excellent reliability and long term stability. Please note that this sensor will not work for temperatures below 0 degree.

Features

  • Relative Humidity and temperature measurement
  • Full range temperature compensation Calibrated
  • Digital signal
  • Long term stability
  • Long transmission distance(>20m)
  • Low power consumption

Tip

More details about Grove modules please refer to Grove System

Applications Ideas

  • Consumption product
  • Weather station
  • Humidity regulator
  • Air conditioner

Hardware Overview

Specifications

Key Specifications

Items Min
PCB Size 2.0cm*4.0cm
Interface 2.0mm pitch pin header
IO Structure SIG,VCC,GND,NC
ROHS YES

Electronic Characterstics

Items Conditions Min Norm Max Unit
VCC - 3.3 - 5 Volts
Measuring Current Supply - 1.3  2.1 mA
Average Current Supply - 0.5 - 1.1 mA
Measuring Range Humidity 20% - 90% RH
Temperature 0 - 50 °C
Accuracy Humidity - - ±5% RH
Temperature ±2 °C
 Sensitivity Humidity - 1% RH
Temperature 1 °C
Repeatability Humidity ±1% RH
Temperature ±1 °C
Long-term Stability ±1% RH/year
Signal Collecting Period 2 S

Usage

When MCU sends a trigger signal, sensor will change from low power consumption mode to active mode. After the trigger signal sensor will send a response signal back to MCU, then 40 bit collected data is sent out and a new signal collecting is trigged.(Note that the 40 bit collected data which is sent from sensor to MCU is already collected before the trigger signal comes.) One trigger signal receives one time 40 bit response data from sensor. Single-bus data is used for communication between MCU and sensor. The communication process is shown below:

It costs 5ms for single time communication.The high-order bit of data sends out first. Signal Data is 40 bit, comprised of 16 bit humidity data, 16 bit temperature data and 8 bit checksum.The data format is:

8bits integer part of humidity+8bits decimal part of humidity
+8bits integer part of temperature+8bits decimal part of temperature
+8bits checksum.

Programming

Connect the Temperature and Humidity sensor to analog port A0.Then you can use the following programme to gain the temperature and humidity of the environment.(The code is for seeeduino only,if you use seeeduino mega you should change the code a little. See below, if you use seeeduino mega, you should change PINC to PINF, change DDRC to DDRF and change PORTC to PORTF)

#define DHT11_PIN 0      // ADC0

byte read_dht11_dat()
{
    byte i = 0;
    byte result=0;
    for(i=0; i< 8; i++){

        while(!(PINC & _BV(DHT11_PIN)));  // wait for 50us
        delayMicroseconds(30);

        if(PINC & _BV(DHT11_PIN))
        result |=(1<<(7-i));
        while((PINC & _BV(DHT11_PIN)));  // wait '1' finish
    }
    return result;
}

void setup()
{
    DDRC |= _BV(DHT11_PIN);
    PORTC |= _BV(DHT11_PIN);

    Serial.begin(9600);
    Serial.println("Ready");
}

void loop()
{
    byte dht11_dat[5];
    byte dht11_in;
    byte i;
    // start condition
    // 1. pull-down i/o pin from 18ms
    PORTC &= ~_BV(DHT11_PIN);
    delay(18);
    PORTC |= _BV(DHT11_PIN);
    delayMicroseconds(40);

    DDRC &= ~_BV(DHT11_PIN);
    delayMicroseconds(40);

    dht11_in = PINC & _BV(DHT11_PIN);

    if(dht11_in){
        Serial.println("dht11 start condition 1 not met");
        return;
    }
    delayMicroseconds(80);

    dht11_in = PINC & _BV(DHT11_PIN);

    if(!dht11_in){
        Serial.println("dht11 start condition 2 not met");
        return;
    }
    delayMicroseconds(80);
    // now ready for data reception
    for (i=0; i<5; i++)
    dht11_dat[i] = read_dht11_dat();

    DDRC |= _BV(DHT11_PIN);
    PORTC |= _BV(DHT11_PIN);

    byte dht11_check_sum = dht11_dat[0]+dht11_dat[1]+dht11_dat[2]+dht11_dat[3];
    // 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(dht11_dat[1], DEC);
    Serial.print("%  ");
    Serial.print("temperature = ");
    Serial.print(dht11_dat[2], DEC);
    Serial.print(".");
    Serial.print(dht11_dat[3], DEC);
    Serial.println("C  ");

    delay(2000);
}

Resources

Help us make it better

Thank you for choosing Seeed. A couple of months ago we initiated a project to improve our documentation system. What you are looking at now is the first edition of the new documentation system. Comparing to the old one, here is the progresses that we made:

  • Replaced the old documentation system with a new one that was developed from Mkdocs, a more widely used and cooler tool to develop documentation system.
  • Integrated the documentation system with our official website, now you can go to Bazaar and other section like Forum and Community more conveniently.
  • Reviewed and rewrote documents for hundreds of products for the system’s first edition, and will continue migrate documents from old wiki to the new one.

An easy-to-use instruction is as important as the product itself. We are expecting this new system will improve your experience when using Seeed’s products. However since this is the first edition, there are still many things need to improve, if you have any suggestions or findings, you are most welcome to submit the amended version as our contributor or give us suggestions in the survey below, Please don’t forget to leave your email address so that we can reply.

Happy hacking