KY-015 Temperature and Humidity Sensor Module

The KY-015 Temperature and Humidity Sensor module provides a digital serial interface to measure environment humidity and temperature. Compatible with various microcontrollers like Arduino, Raspberry Pi and ESP32.

KY-015 Fritzing part image
Arduino KY-015 temperature and humidity sensor module

KY-015 Specifications

This module consist of a DHT11 digital humidity and temperature sensor, a 1 kΩ resistor and 3 male header pins. The DHT11 uses an internal thermistor and a capacitive humidity sensor to determine the surrounding conditions, an internal chip is responsible for converting the readings to a serial digital signal.

Operating Voltage3.3V to 5.5V
Humidity measurement range20% to 90% RH
Humidity measurement accuracy±5% RH
Humidity measurement resolution1% RH
Temperature measurement range0ºC to 50ºC [32ºF to 122ºF]
Temperature measurement accuracy±2ºC
Temperature measurement resolution1ºC
Signal transmission range20m

Connection Diagram

Connect the Power line (middle) and ground (-) to +5 and GND respectively. Connect signal (S) to pin 8 on the Arduino.

KY-015Arduino
SPin 8
middle+5V
GND
Temperature and humidity sensor KY-022 Arduino connection diagram

KY-015 Arduino Code

The following sketch uses pin 8 on the Arduino to serially send and receive data from the KY-015 sensor. Serial communication is archived by sending specific series of high/low signals to the sensor and waiting for a response. Temperature and humidity data is read bit by bit and returned as an array of bytes.

int DHpin = 8; // input/output pin
byte dat[5];   
byte read_data()
{
  byte i = 0;
  byte result = 0;
  for (i = 0; i < 8; i++) {
      while (digitalRead(DHpin) == LOW); // wait 50us
      delayMicroseconds(30); //The duration of the high level is judged to determine whether the data is '0' or '1'
      if (digitalRead(DHpin) == HIGH)
        result |= (1 << (8 - i)); //High in the former, low in the post
    while (digitalRead(DHpin) == HIGH); //Data '1', waiting for the next bit of reception
    }
  return result;
}
void start_test()
{
  digitalWrite(DHpin, LOW); //Pull down the bus to send the start signal
  delay(30); //The delay is greater than 18 ms so that DHT 11 can detect the start signal
  digitalWrite(DHpin, HIGH);
  delayMicroseconds(40); //Wait for DHT11 to respond
  pinMode(DHpin, INPUT);
  while(digitalRead(DHpin) == HIGH);
  delayMicroseconds(80); //The DHT11 responds by pulling the bus low for 80us;
  
  if(digitalRead(DHpin) == LOW)
    delayMicroseconds(80); //DHT11 pulled up after the bus 80us to start sending data;
  for(int i = 0; i < 5; i++) //Receiving temperature and humidity data, check bits are not considered;
    dat[i] = read_data();
  pinMode(DHpin, OUTPUT);
  digitalWrite(DHpin, HIGH); //After the completion of a release of data bus, waiting for the host to start the next signal
}
void setup()
{
  Serial.begin(9600);
  pinMode(DHpin, OUTPUT);
}
void loop()
{
  start_test();
  Serial.print("Humdity = ");
  Serial.print(dat[0], DEC); //Displays the integer bits of humidity;
  Serial.print('.');
  Serial.print(dat[1], DEC); //Displays the decimal places of the humidity;
  Serial.println('%');
  Serial.print("Temperature = ");
  Serial.print(dat[2], DEC); //Displays the integer bits of temperature;
  Serial.print('.');
  Serial.print(dat[3], DEC); //Displays the decimal places of the temperature;
  Serial.println('C');
  byte checksum = dat[0] + dat[1] + dat[2] + dat[3];
  if (dat[4] != checksum) 
    Serial.println("-- Checksum Error!");
  else
    Serial.println("-- OK");
 
  delay(1000);
}

Downloads

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Leave a Comment


10 thoughts on “KY-015 Temperature and Humidity Sensor Module”

  1. I think this really needs “dht.begin();” somewhere in the setup block.

    Reply
    • dht variable is not defined. This code only returns value once

      Reply
  2. Strange, it outputs the values once (sometimes even with correct checksum) but then nothing happens until reboot.

    Reply
  3. BUG with extra semicolon?
    in start_test() lines 30-31:
    if(digitalRead(DHpin) == LOW);
    delayMicroseconds(80); //DHT11 pulled up after the bus 80us to start sending data;

    Reply
    • Hi, thanks for reporting the bug! I updated the code and it should work now.

      Reply