#301 DHT11 Basics
Test basic temperature and humidity readings with the DHT11 sensor.
Notes
The DHT11 sensor is a very cheap and common sensor that provides readings of:
- relative humidity: 20-80% ±5%
- temperature: 0-50°C ±2°C
Circuit Design
I am using a DHT11 that is mounted on an adapter board that includes pull-up resistor for the data line, and a decoupling capacitor, similar to “New Temperature and Relative Humidity Sensor DHT11 Module with Cable for arduino Diy Kit” (aliexpress seller listing).
The schematic below shows the relevant components if a mounting module is not used. Designed with Fritzing: see Basics.fzz.
Demonstration Script
The DHT11 uses a single-wire two-way communications protocol.
For a first test, I’m using a simple DHT11Lib from the arduino playground.
- see LEAP#815 DHT11 Sensor Library Test for a variation using the Adafruit DHT Sensor Library without the unified sensor framework.
- see LEAP#816 DHT11 Unified Sensor Library Test for a variation that uses the Adafruit unified sensor framework.
The Basics.ino sketch simply outputs current readings to the console:
#include "dht11.h"
dht11 DHT11;
const int DHT11_PIN = 2;
void setup() {
Serial.begin(115200);
}
void loop() {
if (read_sensor() == DHTLIB_OK) display_readings();
delay(2000);
}
int read_sensor() {
int status = DHT11.read(DHT11_PIN);
Serial.print("Read sensor: ");
switch (status) {
case DHTLIB_OK:
Serial.println("OK");
break;
case DHTLIB_ERROR_CHECKSUM:
Serial.println("Checksum error");
break;
case DHTLIB_ERROR_TIMEOUT:
Serial.println("Time out error");
break;
default:
Serial.println("Unknown error");
break;
}
return status;
}
void display_readings() {
Serial.print("Humidity (%): ");
Serial.println((float)DHT11.humidity, 2);
Serial.print("Temperature (°C): ");
Serial.println((float)DHT11.temperature, 2);
}
Sample console output:
