DHT-11 | DHT-22 | |
---|---|---|
Humidity range | 20%-80%RH (±5%RH) | 0%-100%RH (±2%RH) |
Temperature range | 0-50°C (±2°C) | -40-80°C (±0.5°C) |
Measurement time | 1s per sample | 2s per sample |
There's more humidity sensors around which requires less power to operate, like BME280 or Si7021. See this comparison for in-depth information on their accuracy.
Start by connecting the radio module.
Sensor | Arduino | Comment |
---|---|---|
- | GND | Marked black |
+ | VCC (3.3 - 5.5V) | Marked red |
out (middle) | Digital pin 3 | Marked green |
This example uses a modified version of the external DHT library, which is included in the MySensors external examples. Please install it and restart the Arduino IDE before trying to compile.
For the DHT-11, you can find an example created by michlb1982 here.
/**
* The MySensors Arduino library handles the wireless radio link and protocol
* between your home built sensors/actuators and HA controller of choice.
* The sensors forms a self healing radio network with optional repeaters. Each
* repeater and gateway builds a routing tables in EEPROM which keeps track of the
* network topology allowing messages to be routed to nodes.
*
* Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
* Copyright (C) 2013-2015 Sensnology AB
* Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
*
* Documentation: http://www.mysensors.org
* Support Forum: http://forum.mysensors.org
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* version 2 as published by the Free Software Foundation.
*
*******************************
*
* REVISION HISTORY
* Version 1.0: Henrik EKblad
* Version 1.1 - 2016-07-20: Converted to MySensors v2.0 and added various improvements - Torben Woltjen (mozzbozz)
*
* DESCRIPTION
* This sketch provides an example of how to implement a humidity/temperature
* sensor using a DHT11/DHT-22.
*
* For more information, please visit:
* http://www.mysensors.org/build/humidity
*
*/
// Enable debug prints
#define MY_DEBUG
// Enable and select radio type attached
#define MY_RADIO_RF24
//#define MY_RADIO_RFM69
//#define MY_RS485
#include <SPI.h>
#include <MySensors.h>
#include <DHT.h>
// Set this to the pin you connected the DHT's data pin to
#define DHT_DATA_PIN 3
// Set this offset if the sensor has a permanent small offset to the real temperatures.
// In Celsius degrees (as measured by the device)
#define SENSOR_TEMP_OFFSET 0
// Sleep time between sensor updates (in milliseconds)
// Must be >1000ms for DHT22 and >2000ms for DHT11
static const uint64_t UPDATE_INTERVAL = 60000;
// Force sending an update of the temperature after n sensor reads, so a controller showing the
// timestamp of the last update doesn't show something like 3 hours in the unlikely case, that
// the value didn't change since;
// i.e. the sensor would force sending an update every UPDATE_INTERVAL*FORCE_UPDATE_N_READS [ms]
static const uint8_t FORCE_UPDATE_N_READS = 10;
#define CHILD_ID_HUM 0
#define CHILD_ID_TEMP 1
float lastTemp;
float lastHum;
uint8_t nNoUpdatesTemp;
uint8_t nNoUpdatesHum;
bool metric = true;
MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
DHT dht;
void presentation()
{
// Send the sketch version information to the gateway
sendSketchInfo("TemperatureAndHumidity", "1.1");
// Register all sensors to gw (they will be created as child devices)
present(CHILD_ID_HUM, S_HUM);
present(CHILD_ID_TEMP, S_TEMP);
metric = getControllerConfig().isMetric;
}
void setup()
{
dht.setup(DHT_DATA_PIN); // set data pin of DHT sensor
if (UPDATE_INTERVAL <= dht.getMinimumSamplingPeriod()) {
Serial.println("Warning: UPDATE_INTERVAL is smaller than supported by the sensor!");
}
// Sleep for the time of the minimum sampling period to give the sensor time to power up
// (otherwise, timeout errors might occure for the first reading)
sleep(dht.getMinimumSamplingPeriod());
}
void loop()
{
// Force reading sensor, so it works also after sleep()
dht.readSensor(true);
// Get temperature from DHT library
float temperature = dht.getTemperature();
if (isnan(temperature)) {
Serial.println("Failed reading temperature from DHT!");
} else if (temperature != lastTemp || nNoUpdatesTemp == FORCE_UPDATE_N_READS) {
// Only send temperature if it changed since the last measurement or if we didn't send an update for n times
lastTemp = temperature;
// apply the offset before converting to something different than Celsius degrees
temperature += SENSOR_TEMP_OFFSET;
if (!metric) {
temperature = dht.toFahrenheit(temperature);
}
// Reset no updates counter
nNoUpdatesTemp = 0;
send(msgTemp.set(temperature, 1));
#ifdef MY_DEBUG
Serial.print("T: ");
Serial.println(temperature);
#endif
} else {
// Increase no update counter if the temperature stayed the same
nNoUpdatesTemp++;
}
// Get humidity from DHT library
float humidity = dht.getHumidity();
if (isnan(humidity)) {
Serial.println("Failed reading humidity from DHT");
} else if (humidity != lastHum || nNoUpdatesHum == FORCE_UPDATE_N_READS) {
// Only send humidity if it changed since the last measurement or if we didn't send an update for n times
lastHum = humidity;
// Reset no updates counter
nNoUpdatesHum = 0;
send(msgHum.set(humidity, 1));
#ifdef MY_DEBUG
Serial.print("H: ");
Serial.println(humidity);
#endif
} else {
// Increase no update counter if the humidity stayed the same
nNoUpdatesHum++;
}
// Sleep for a while to save energy
sleep(UPDATE_INTERVAL);
}